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8/3/2019 Animal Proteins

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BYH U G H G A R N E R B E N N E T T , M . S c . ( L E E D S )MEMBER OP THE SOCIETY OF LEATHER TRADES' CHEMISTS; FORMERLYASSISTANT LECTURER AND DEMONSTRATOR AT THE LEATHERINDUSTRIES DEPARTMENT OF THEUNIVERSITY OF LEEDSAUTHOR OF "THE MANUFACTURE OF LEATHER"


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G E N E R A L P R E F A C ET H E r a p i d d e v e l o p m e n t o f A p p l i e d C h e m i s t r y i n r e c e n t y e ah a s b r o u g h t a b o u t a r e v o l u t i o n i n a l l b r a n c h e s o f t e c h n o l o gT h i s g r o w t h h a s b e e n a c c e l e ra t e d d u r i n g t h e w a r , a n d tB r i t i s h E m p i r e h a s n o w a n o p p o r t u n i t y o f i n c r e a s i n g i n d u s t r i a l o u t p u t b y t h e a p p H c a t io n of t h i s k n o w l e d g e t o tr aw m at er i a l s avai l ab l e i n t h e d if ferent p a r t s of t h e wo rT h e sub j ec t i n t h i s seri es of ha nd bo ok s will be t r e a t e d f rot h e c h e m i c a l r a t h e r t h a n t h e e n g in e e ri n g s t a n d p o i n t . Ti n d u s t r i a l a s p e c t w i l l a l s o b e m o r e p r o m i n e n t t h a n t h a t t h e l a b o r a t o r y . E a c h v o l u m e w ill b e c o m p l e t e i n itself, awi l l g i ve a gener a l sur vey of t he i ndus t r y , showi ng hoc h e m i c a l p r i n c i p l e s h a v e b e e n a p p l i e d a n d h a v e a f f e c tm a n u f a c t u r e . T h e in flu en c e of n e w i n v e n t i o n s o n tdevel opment of t he i ndus t r y wi l l be shown, as a l so te f f ec t of i ndus t r i a l r equi r ement s i n s t i mul a t i ng i nvent i oHi s t or i c a l not es wi l l be a f ea t ur e i n deal i ng wi t h td i f f er ent br anc hes of t he subj ec t , but t hey wi l l be kew i t h i n m o d e r a t e l i m i t s . P r e s e n t t e n d e n c i e s a n d p o s si bf u t u r e d e v e l o p m e n t s w i ll h a v e a t t e n t i o n , a n d s o m e s p aw i ll b e d e v o t e d t o a c o m p a r i so n of i n d u s t r i a l m e t h o d s apr ogr ess i n t h e c hief pr od uc i ng c ou nt r i es . T he r e wi l l b egeneral bibl iography, and also a selec t bibl iography to fol lo


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v i GENERAL PREFACEt h e o r t h o d o x t e x t b o o k m a n n e r , n o t o nl y t o m a k e t li e t r e a t -m e n t o r i g i n a l , b u t a l s o t o a p p e a l t o t h e v e r y l a r g e c l a s s o fr e a d e r s a l r e a d y p o s s e s s i n g g o o d t e x t b o o k s , o f w h i c h t h e r ea r e q ui t e suf f ic i e n t. T h e bo ok s sho ul d a lso b e f ound use fu lb y m e n of a ff ai rs h a v i n g n o s p e c i a l t e c h n i c a l k n o w l e d g e , b u tw h o m a y r e q u i r e f r o m t i m e t o t im e t o re fe r t o t e c h n i c a lm a t t e r s i n a b o o k of m o d e r a t e c o m p a s s , w i t h r e fe re n c e s t ot h e l a r g e s t a n d a r d w o r k s f o r f ti lle r d e t a il s o n s p e c i a l p o i n t si f r e q u i r e d .T o t h e a d v a n c e d s t u d e n t t h e b o o k s s h o u l d b e e sp ec ia lly -v a l u a b l e . H i s m i n d i s o f t e n c r a m m e d w i t h t h e h a r d f ac t sa n d d e t a i ls o f h i s s u b j e c t w h i c h c r o w d o u t t h e p o w e r ofr e a li z in g t h e i n d u s t r y a s a w h o l e . T h e s e b o o k s a r e i n t e n d e dt o r e m e d y s u c h a s t a t e o f a f f ai r s. W h i l e r e c a p i t u l a t i n g t h ee s s e n t i a l b a s i c f a c t s , t h e y w i ll a i m a t p r e s e n t i n g t h e r e a l i t yof t h e l i v in g i n d u s t r y . I t h a s l o n g b e e n a d r a w b a c k of o u rt e c h n i c a l e d u c a t i o n t h a t t h e c o l le g e g r a d u a t e , o n c o m m e n c i n gh i s i n d u s t r i a l c a r e e r , i s p o s i t iv e l y h a n d i c a p p e d b y h i sa c a d e m i c k n o w l e d g e b e c a u s e of h is l a c k of in f o r m a t i o n o nc u r r e n t i n d u s t r i a l c o n d i t i o n s . A b o o k g i v in g a c o m p r e -h e n s i v e s u r v e y o f t h e i n d u s t r y c a n b e o f v e r y m a t e r i a la s s i s t a n c e t o t h e s t u d e n t a s a n a d j u n c t t o h i s o r d i n a r y t e x t -books , a nd t h i s i s one of t he ch i e f obj e c t s of t he pr e se ntse r i e s . T h o s e a c t u a l l y e n g a g e d i n t h e i n d u s t r y w h o h a v es p e c i a l i z ed i n r a t h e r n a r r o w l i m i t s w i l l p r o b a b l y fin d t h e s eb o o k s m o r e r e a d a b l e t h a n t h e la rg e r t e x t b o o k s w h e n t h e yw i s h t o r e f r es h t h e i r m e m o r i e s i n r e g a r d t o b r a n c h e s of t h es u b j e c t w i t h w h i c h t h e y a r e n o t i m m e d i a te l y c o n c e r n ed .

T h e v o l u m e w i l l a l s o s e r v e a s a g u i d e t o t h e s t a n d a r dl i t e r a t u r e o f t h e s u b j e c t , a n d p r o v e o f v a l u e t o t h e c o n -s u l t a n t , s o t h a t , h a v i n g o b t a i n e d a c o m p r e h e n s iv e v ie w oft h e w h o l e i n d u s t r y , h e c a n g o a t o n c e t o t h e p r o p e ra u t h o r i t i e s f o r m o r e e l a b o r a t e i n f o r m a t i o n o n s p e c i a l p o i n t s ,a n d t h u s s a v e a c o u p l e o f d a y s s p e n t in h u n t i n g t h ro u g h , t h el i br a r i e s of sc i e nt i f i c soc i e t i e s .A s f ar a s t h i s c o u n t r y i s c o n c e r n e d , i t is b e li e v ed t h a tt h e g e n e r a l s c h e m e o f t h i s s e r i e s o f h a n d b o o k s i s u n i q u e ,a n d i t i s c o n f i d e n t l y h o p e d t h a t i t w i ll s u p p l y m e n t a l


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GENERAL PREFACEm unitions for tlie com ing industrial war. I h av e beefortunate in securing writers for th e different vo lum es w hare specially connected with the several departments Industrial Chemistry, and trust that the whole series wcontribute t o th e further dev elopm ent of app lied ch em istrthroughout the Empire.

S A M U E L R I D E A I . .


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A U T H O R ' S P R E F A C EI T h a s b e e n t h e a u t h o r ' s c h ief c o n c e r n t h a t t h i s v o l u mshoul d fu l f i l i t s own pa r t i n t he progra mme se t for t h D r . E i d e a l ' s G e n e r a l P r e f a c e .

T h e l e a t h e r , g l u e , a n d k i n d r e d t r a d e s h a v e b e e n fm a n y y e a r s r e c o g n i z e d a s c h e m i c a l i n d u s t r i e s , b u t t h e g r ede ve l opme nt of co l l o i d che mi s t ry i n t he l a s t fe w ye a rs hg i v e n t h e s e t r a d e s a m o r e d e f i n i t e s t a t u s a s s u c h , a n d t hc a n n o w b e p l a c e d i n t h e c a t e g o r y o f a p p l i e d p h y s i cc h e m i s t ry . T h e t i m e is p r o b a b l y n o t f ar d i s t a n t w hsome knowl e dge of pure physi ca l che mi s t ry wi l l be a f ie s s e n t i a l t o s t u d e n t s , c h e m i s t s , c h e m i c a l e n g i n e e r s , a n d a ll e n g a g e d i n t h e s e i n d u s t r i e s in s u p e r v i s io n , a d m i n i s t r a t i oo r c o n t r o l . I t i s h o p e d t h a t t h i s v o l u m e w i ll s t i m u l a t e ts t u d y o f t h e s e i n d u s t r i e s f r o m t h a t s t a n d p o i n t .

A s t h e a u t h o r h a s p r e v i o u s l y w r i t t e n u p o n o n e of ti n d u st ri e s i nv o l ve d h e r e in ( " T h e M a n u f a c t u r e of l e a t h e r Con st a bl e & Co. ) , he ha s , ra t h e r i n e v i t a bl y , foun d i t d iff ict o a v o i d a l t o g e t h e r h i s o w n p h r a s e o l o g y . T h e c h a n g e s a d e c a d e , h o w e v e r , t o g e t h e r w i t h t h e w i d e r f i e l d a n d n e wvi e w-poi nt , ha ve ma de poss i b l e a ra di ca l d i f fe re nce t r e a t m e n t .T h e a u t h o r d e s i r e s t o a c k n o w l e d g e t h e h e l p h e hr e c e i v e d f r o m t h e m a n y b o o k s , e s s a y s , a n d r e s e a r c h e s w h ia r e m e n t i o n e d i n t h e r e f e r e n c e s a t t h e e n d o f e a c h s e c t i oe sp ec i ally t o P r o c t e r ' s " P r i n c i p l e s of L e a t h e r M a n u f a c t u ra n d a ls o t o t h a n k D r . R i d e a l fo r m a n y u s e fu l s u g g e s t i o nT h e a u t h o r w o u l d l ik e a ls o t o a c k n o w l e d g e h e r e h i s i n d e b t ene ss (a s we l l a s t ha t of t he t ra de ge ne ra l l y ) t o t he work


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x AUTHOR'S PREFACED r . J . G o r d o n P a r k e r , w h o , t h r o u g h h i s r e s e a rc h e s , l e c t u r e s ,a n d t e a c h i n g w o r k , h a s d o n e m o r e t h a n a n y o t h e r m a n t od i s s e m i n a t e a k n o w l e d g e o f p r a c t i c a l m e t h o d s o f t a n n i n g .

T h e a u t h o r ' s t h a n k s a r e al s o d u e t o h i s b r o t h e r , M r . W .G o r d o n B e n n e t t , M . S c , A . I . C . , M . C ., fo r a s s is t a n c e i n p ro o frev i s i o n , an d t o h i s fa t h er , R ev . J o h n B en n e t t , fo r so mel i t e r a r y c r i t i c i s m .H . G A R N E R B E N N E T T .

BEVERLEY,June t 1921.


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CONTENTSGENERAL PREFACE vAUTHOR'S PREFACE ixCONTENTS xiINTRODUCTION I

PART I.HI D ES F OR HEAVY LEAT HERS .

SECTION1. TH E RAW M ATE RIAL OF HEAVY L EATHE RS . . . 72. TH E PREPARATION OF PE L T 163. VEGETABLE TANNAGE 274. FINISHING PROCESSE S 495. SOLE LE ATHER 556. BEL TING LE ATHER 657. HARNESS L E ATHE R. . 718. UPPER LEATHERS . . 7 69. BAG L E ATHER 35

10. PICKING BAND BUTTS gO

PART II.


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x ii CONTENTSSECTION pAGE2. GOATSK INS - 993 . S E A L S K I N S I 0 64. S H E E P S K I N S n o5. CAL FSKINS i 2 o6 . J AP A N NE D A ND E N A M E L L E D L E A T HE R S . . . . 1 2 3

P A R T I I I .C H R O M E L E A T H E R S .

1. T H E N A T U R E O F C H R O M E L E A T H E R S 1272 . G E N E R A L M E T H O D S O F C H RO M E L E A TH E R M A N U FA C TU R E 1393 . CH RO M E CA L F 1564 . CH RO M E G O A T A ND S H E E P 1635 . H E A V Y C H R OM E L E A T H E R S 170

P A R T I V .M I S C E L L A N E O U S T A N N A G E S .

1. ALUM TANNAGE S 1742. FA T TANNAG ES 1783. OI L TANNAGES 1814 . F O RM A L D E H Y D E T A N N A G E 1855 . S Y N T H E T IC T A N N I N G M A T E RI A L S 1876. COM BINATION TANNA GE S 1917 . T H E E V O L U T IO N O F T H E L E A T H E R IN D US TR Y . . . 1 9 4 .

P A R T Y .G E L A T I N E A N D G L U E .

1 . P RO P E RT I E S O F G E L A T I N E A N D G L U E 2002 . RA W M A T E RI A L S A ND P RE L I M I N ARY T RE A T M E N T . . 220


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CONTENTS xSECTION PA3. E XTRACTION .

4. CLARIFICATION AND D E COLO RIZATION 5. BL EA CHING 6. E VAPORATION 7. COOLING AND D RY ING 28. USE S OF GE L ATINE AND GL UE 9. THE E VOL UTION OF THE GE L ATINE AND GL UE IND US TRY

P A R T V I .M IS C E L L A NE O U S PR O T E I N S A ND B Y E - P RO D U C T S .

1. BYE -PROD UCTS OF T H E L E A TH E R TRAD E S . . . . 2. BYE-PRODUCTS OF THE GE L ATINE AND GL UE TRAD E S . 3. FOOD PROTE INS 4 . M ISCELLANEOUS ANIM AL PROTE INS

INDEX 2


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A N I M A L P R O T E I N S

I N T R O D U C T I O NP R O T E I N S a r e o r g a n i c c o m p o u n d s o f n a t u r a l o r i g i n , b e i n gf o u n d i n p l a n t s a n d i n a n i m a l s , t h o u g h m u c h m o r e p l e n t i -f ully i n t h e l a t t e r . T h e y a r e c o m p o u n d s of g r e a t c o m p l e x i t yof c o m p o s i t io n , a n d of v e r y h i g h m o l e c u l a r w e i g h t . T h ec o n s t i t u t i o n of n o n e of t h e m is f ully u n d e r s t o o d , b u t a l t h o u g ht h e r e a r e a g r e a t n u m b e r o f d i f f e r e n t i n d i v i d u a l p r o t e i d s ,t h e y p r e s e n t t y p i c a l r e s e m b l a n c e s a n d d i v e r g e n c e s w h i c hserve to d i f ferent ia te them from other groups of organicbodies , and a lso f rom one another .P r o t e i n s r e s e m b l e o n e a n o t h e r i n b o t h p r o x i m a t e a n du l t i m a t e a n a l y s i s . T h e y c o n t a i n t h e u s u a l e l e m e n t s i no r g a n i c c o m p o u n d s , b u t i n p r o p o r t i o n s w h i c h d o n o t v a r yo v e r v e r y w i d e l im i t s . T h i s r a n g e of v a r i a t i o n i s g i v e na p p r o x i m a t e l y b e l o w :

E lement. Per cen t.C a r b o n 4 9 t o 5 5H yd ro ge n 6*4 t o 7*3O x y g e n 1 7 t o 2 6N i t r o g e n 1 3 t o 1 9S u lp h u r 0*3 t o 3*0T h e m o s t c h a r a c t e r i s t i c f e a t u r e o f t h e p r o t e i n g r o u p i st h e a m o u n t of n i t r o g e n u s u a l l y p r e s e n t . T h i s i s g e n e r a l l yn e a r e r t h e h i g h e r l i m i t , s e l d o m f a l l i n g b e l o w 1 5 p e r c e n t .T h i s r a n g e f o r t h e n i t r o g e n c o n t e n t i s d e t e r m i n e d l a r g e l yb y t h e n a t u r e of c o n s t i t u e n t g f o u p s w h i c h g o t o f o r m t h ep r o t e i d m o l e c u l e . R o u g h l y s p e a k i n g , p r o t e i n s c o n s i s t of


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2 ANIMAL PROTEINSc o m p o u n d s a t t a c h e d . I n t h e s e c h a i n s a n a c i d r a d i c a l m a yc o m b i n e w i t h t h e a m i d o g r o u p o f a n o t h e r a m i d o a c i d , t h eac id group of the la t te r c ombining wi th an amido group ofa n o t h e r a m i d o a c i d , a n d s o o n . H y d r o g e n m a y b e s u b s t i t u t e din thes e c hains by a lk yl or a rom at ic groups . T h ere i sobvious ly inf in i te pos s ibi l i ty of var ia t ion in c ons t i tu t ionfor c om pound s of th is c harac ter , th e genera l na t ur e of whic hvar ies very l i t t le . Pra c t ic a l ly a ll of th e pro te ins a re foundi n t h e c ^ ^ d ^ t a t e ^ a n d t h i s m a k e s t h e m v e ry diffic ult t op u r if y a n d r e n d e r s t h e u l t i m a t e a n a l y s i s in m a n y c a s esdoub tful . I t is , for exa m ple , often difficult to asc ertaintheir mois ture c ontent , for many are eas i ly hydrolyzed wi thwater only , and many par t eas i ly wi th the e lements of water ,w h i l s t o n t h e o t h e r h a n d m a n y a r e l y o p h i k c o j l q i d s a n dprac t ic a l ly c ann ot be de hy d ra te d or driec T. A few, s uc has ge la t in and s ome a lbumins , have been c rys ta l l ized .

T he c ons t i tuent groups have been inves t iga ted c hief lyb y h y d ro l y t ic m e t h o d s . T h e c h a i n s of a m i d o a c i d s a r es p l i t u p d u r i n g h y d r o l y s i s , a n d i n d i v i d u a l a m i d o a c i d s m a yt h u s b e s e p a r a t e d . T h e h y d r o l y s i s m a y b e a s s is t ed e i th e rby ac ids , a lkalies or ferments , but follows a different coursea c c o r d in g t o t h e n a t u r e of t h e a s s i s t a n t . U n d e r a p p r o x i -m a t e l y c o n s t a n t c o n d i t i o n s o f h y d r o l y s i s , t h e p r o d u c t so b t a i n ed ar e i n a p p r o x i m a t e l y c o n s t a n t p r o p o r ti o n s , a n dthis fac t has been ut i l ized by Van S lyke in devis ing a methodof pro xim ate analy s is . I t i s no t pos s ible in th is volum e toenter deeply in to the c ons t i tu t ion of the d i f ferent prote ids .R e f e r e n c e m u s t b e m a d e t o w o r k s o n p u r e c h e m i s t r y ,es pec ia lly to tho s e on ad va nc ed organic c hem is t ry . I t wi llbe in teres t ing, however , to ment ion s ome of the amidoac ids an d grou ps c om m only oc c urr ing in prote ids . T hes ec om pris e orn i th ine ( i : 4 d iamido valer ic ac id) , lys ine ( 1 : 5diamido-c aproic ac id) , a rginine (1 am ido, 4 guanidine va ler ica c id ) , his t id ine , g lyc ine (amidoac et ic ac id) , a lanine (amidopropionic ac id) , amido-valer ic ac id (amido-is o-c aproic ac id) ,l iac ine , pyrol l id ine c arboxyl ic ac id , as par t ic ac id , g lutamicac id (amido-glutar ic ac id) , phenyl-a lanine , s er ine (hydroxy-


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INTRODUCTION 3i ndol de r i va t i ve s {e.g. t r y p t o p h a n e a n d s k a t o l a c e t i c a c i d ) ,cys t i ne ( a t h i ose r i ne a nhydr i de ) , g l ucosa m i ne , a nd ur e a .Th e r e a r e a fe w ge n e r a l r e a c t i ons wh i ch a r e typ i c a l of a l lp r o t e i n s , a n d w h i c h c a n u s u a ll y b e t r a c e d t o d e fi n it e g r o u p i n g si n t h e m o l e c u l e . A m o n g s t t h e s e i s t h e b i u r e t r e a c t i o n : ap i n k c o l o u r o b t a i n e d b y a d d i n g a t r a c e o f c o p p e r s u l p h a t ea n d a n e xce ss of c a us t i c soda . Th i s i s c a use d b y t h e b i ur e t ,N H ( C O . N H 2 ) 2 r a d i c a l o r b y s i m i l a r d i a c i d a m i d e g r o u p s ,e.g. m a l o n a m i d e , o x a m i d e , g l y c i n e a m i d e . A n o t h e r g e n e r a lr e a c t i o n is w i t h " M i l l o n ' s r e a g e n t / ' a s o l u t io n of m e r c u r i cn i t r a t e c o n t a i n i n g n i t r o u s f um e s . O n w a r m i n g t h e p r o t e i dw i t h t h i s r e a g e n t , a c u r d y p i n k p r e c i p i t a t e o r a r e d c o l o u ri s o b t a i n e d . T h i s r e a c t i o n i s c a u s e d b y t h e t y r o s i n e g r o u p(p. o x y a a m i d o p h e n y l- p ro p i o n ic a c i d ) . A n o t h e r g e n e r a lr e a c t i on is t o boi l t h e pr o t e i n wi t h 1 : 2 n i t r i c a c i d f or so m eda ys . A yellow f locculent prec ipi t a te of " x a n t h o p r o t e i ca c i d " i s ob t a i ne d , a nd t h i s d i ssol ves i n a m m on i a a n d c a u s t i ca l ka li e s w i t h a br o w n or or a nge - r e d co l our . A n o t h e rcha r a c t e r i s t i c of pr ot e i ns i s t ha t on dr y d i s t i l l a t i on t he y y i e l dm i xt ur e s of py r i d i n e C 5 H 6 N, pyr r ol C 4 H 5 N , a n d t h e i rd e r i v a t i v e s .

On t he subdi vi s i on , c l a ss i f i ca t i on a nd nom e ncl a t ur e oft he pr ot e i ns m uch i nk ha s be e n spi l l e d , a nd i t i s i m poss i b l ei n t h i s v o l u m e t o g o i n t o t h e v a r i o u s s y s t e m s w h i c h h a v eb e e n s u g g e s t e d . I t s h o u l d b e n o t e d , h o w e v e r , t h a t s o m ew r i t e r s ha bi t u a l l y use t h e t e r m s " pr o t e i d " or " a l bu m i no i d "a s syn on ym s for pr o t e i n . T he c l a ss if ica t i on of pr ot e i n sa d op t e d i n t h i s wor k i s use d be c a use i t i s t h e m os t s u i t a bl efo r a v o l u m e o n i n d u s t r i a l c h e m i s t r y a n d h a s t h e a d d i t i o n a lm e r i t s t h a t i t i s s i m pl e a nd is a l r e a dy u se d i n se v e r a ls t a n d a r d w o r k s o n i n d u s t r i a l c h e m i s t r y . I t is b a s e d u p o nt h e b e h a v i o u r of t h e p r o t e i n s to w a r d s w a t e r , a m a t t e r ofo b v i o u s m o m e n t i n m a n u f a c t u r i n g p r o c e s s e s . O n t h i s b a s i sp r o t e i n s m a y b e d i v id e d in t o y k l b u m i n ^ l c e r a t i n s a n d g d a t i n s .C ol d wa t e r d i ssol ve s t he a l bum i ns , doe s not a f f e c t t he


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4 ANIMAL PROTEINS7 -75 -C, th e ge lat in s ( if swollen) dissolve readi ly, wh i ls tt h e k e r a t i n s o n ly d i ss o lv e a t t e m p e r a t u r e s a b o v e i o o C.A l bum i ns an d ke r a t i n s ma y be d i s t i ngui s hed a l s o fr omg e l a t i n s b y a d d i n g a c e t i c a c i d a n d p o t a s s i u m f e r r o c y a n i d et o t h e i r a q u e o u s s o l u t io n s . A l b u m i n s a n d k e r a t i n s g i ve apr ec i p i t a t e , ge l a t i ns do no t . A no t he r d i s t i ngui s hi ng r eac t i oni s t o boi l w i t h a l c ohol , w as h w i t h e t her , an d hea t w i t h h yd r o-ch lor ic ac id (S .G. 1*2). A lbu m ins give a violet co lour ,ker a t i ns and gel a t i ns do not .

A l b u m i n s m a y be f irst discu ssed. T h ey are typif iedby t he c as e in of m i l k an d by w h i t e of egg . T he i r s o l ut i onsin water are faint ly alkal ine, opt ical ly ac t ive, and laevo-r o t a t o r y . T h e y a re c o a g u l a t e d b y h e a t a n d a ls o b y m i n e r a la c i d s, a lc o h o l, a n d b y m a n y p o i s o n s . T h e t e m p e r a t u r e ofc oagul a t i on ( us ual l y about 72 0 C.) is affected by minerals a l t s, t h e effec t be i ng i n l yo t r op e or der ( s ee P a r t V . , S ec t i onI . ) . T h e c o a g u l a te d a l b u m i n b e h a v e s i n m o s t r e s p e c t s l ik ea ker a t i n . S ome of t h e a l bum i ns ( g l obuli ns ) a r e , s t r i c t l ys peaki ng, not s o l ubl e i n c o l d w at er , but r eadi l y d i s s ol ve i nw eak s ol ut ions of s a l t . T h e a l bu m i ns ar e c oag ul a t ed f romt hes e s ol uti ons , as us ua l , w h en he at ed . I n t o t h i s s pec i a lclass fall m yo sin (of th e m usc les), f ibrinogen (of th e bloo d)an d vi te l li n (of egg yol k ) . B y a gen t l e or l i mi t ed hy dr o l ys i sof the albumins with di lute ac ids in the cold, a group ofc o mpo unds c a l led a l bum i nat es a r e ob t a i ned . T h ey dis s ol vei n e i t her ac i ds or a l ka l ies , an d ar e pr e c i p i t a t ed by ex ac tneut r a l i za ti on . T h ey m ay a ls o be " s a l t ed " ou t by ad di n gs o d iu m c h lo r id e o r m a g n e s i u m s u l p h a t e . T h e y a r e n o tc oagu l a ted by hea t . A f t er f ur t her hyd r ol ys i s w i t h e i t heracids , a l ka l i es or f e r ment s , ver y s ol ubl e c ompounds ar eobt a i ned c a l led a l bum i n pep t ones or a l bum os es . T h es e ar esoluble in alkalies , ac ids an d wate r , an d are readi ly h y d ro -l yzed f ur ther i n t o ami do ac i ds an d a d d am i des . T h ey ar ever y s i mi l ar t o t he pept ones obt a i ned f r om ker a t i ns andgel a ti ns . T hey ar e no t c o agul a t ed by h ea t .

K e r a t i n s ar e t ypif ied by t he ha i r of ani m al s . T he ys of t en s omew hat i n c o l d w at er and even mor e i n hot w at er ,bt t t axe n o t dissolved un t i l digested for som e t im e qt t e r n-


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INTRODUCTION 5r a t u r e s e x c e e d in g i o o C . W i t h s o m e k e r a t i n s , h o w e v e r ,

a t e r , a n d o n b o il in g w i t h w a t e r h y d r o g e n s u l p h i d e i sT h e s u l p h u r c o n t e n t of k e r a t i n s i s o f te n g r e a t e ra n t he a ve ra ge for pro t e i ds . Al l ke ra t i n s a re d i sso l ve dn d h y d r a t e s , e.g. a so l u t i on of sod i um sul p hi de . I n so l u-i o n s o f t h e h y d r a t e s o f t h e a l k a l i a n d a l k a l i n e e a r t h m e t a l s ,r a t i n s b e h a v e d i ff e re n tl y . S o m e d i ss o lv e w i t h g r e a t e a s e ,

if d i g e s t e d w i t h h o t c a u s t i c s o d a . T h e y a r e d is s o l v e d( w i t h h y d r o l y s i s ) b y h e a t i n g w i t h m i n e r a l a c i d s , y i e l d i n gt o n e s a n d e v e n t u a l l y a m i d o a c i d s , a c i d a m i d e s , e t c .a n y k e r a t i n s h a v e a c o m p a r a t i v e l y lo w c o n t e n t of n i t r o g e n .G e l a t i n s a re ve ry d if ficu lt t o d i s t i ngu i sh f rom one

h e y a r e a ls o v e r y re a d i l y h y d r o l y z e d e v e n w i t h w a t e r , a n de p r o d u c t s of h y d r o l y s i s a r e e v e n m o r e s i m i l a r . T h ek n o w n t o g e t h e r , c o m m e r c i a l ly , u n d e r t h ene ral n a m e of ge lat in e . G elat in s of different or igin, ho w -h a v e u n d o u b t e d l y a d i ff er en t c o m p o s i t io n , t h e n i t r o g e no n t e n t b e i n g v a r i a b l e . I f t h e g e l a t i n s a r e n o t b l e a c h e d

y a r e c a l le d " g l u e . " G e l a ti n e i s c o l o ur le ss , t r a n s p a r e n t ,f t a s t e a n d sme l l . I t i s usua l l y b r i t t l e . I t s S .G. i s0 C . a n d d e c o m p o s e s . I t i si n orga ni c so l ve n t s . W he n swe l li ng i n c o l d w a t e rm a y a bs orb up t o 12 t i me s i t s ow n w e i gh t of w a t e r . T h een p ro d u c t is c a l led a "je lly*." Je l l ies easi ly m e l t onhi s " se ts " a ga in to a je l ly on c ool ing, ev en if o nly 1 pe re nt , ge l a t i n (or le ss ) be pre se nt . T h e so l u t i on i s op t i c a l l y

S o m e o b s e r v e rs h a v e t h o u g h t t h a t , t h e d if fe re n t


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6 ANIMAL PROTEINSof a lu min iu m, c h r o m iu m an d i r o n , an d of mer cu r ic c h lo rid e ,z in c s u l p h a te , a m m o n i u m s u l p h a t e , p o t a s s i u m c a r b o n a t e ,.acidified br ine. M a n y of th es e pre c ipi ta t ion s ha ve analogiesfn l e a th e r m a n u f a c t u r e ( s ee P a r t s I . t o I V . ) . T h e g e l a t inp ep to n es o r g e la to ses ar e f o r med b y h y d r o ly s is wi th ac id s ,alkal ies, ferment or even by digest ion with hot water only .A more detai led descr ipt ion of the propert ies of gelat ine isg iv en in P a r t V. , S ec t io n I . Gela t in e i s so met im es ca l led" glut in " and " o s s e i n . "

A n i m a l s a r e m u c h t h e m o s t i m p o r t a n t s o u r c e o f p r o t e i n s ,esp ec ia l ly o f th o se wh ich ar e o f imp o r tan ce in in d u st r ia lch em istr y . Pr o te in s o c c u r in n ear ly ev er y p a r t of a lla n im a l s, a n d t h e " p r o t o p l a s m " of t h e l iv in g c e ll i s its el fa p r o te in . Th e k er a t in s in c lu d e th e h o r n y t i ssu es o fa n i m a l s : t h e e p i d e r m i s p r o p e r , t h e h a i r, h o r n s , h o of s,nails, c laws, th e seb ac eo u s an d su d o r i fer o u s g lan d s an d d u c ts ,an d also th e elast ic f ibres. T h e gelat in s are obta ined fromthe collagen of th e sk in f ibres, t h e bon es, ten do ns, l iga m en ts,car ti lag es, e tc . F is h b la d d er s y ie ld a s t r o n g g ela t in . T h ealb u min s ar e o b ta in ed f r o m th e o v a , b lo o d , ly m p h , mu sclesan d o th er in ter n a l o r g an s of an ima ls .

The classif icat ion of proteins herein adopted f i ts in wellw i t h t h e s c o p e a n d p u r p o s e of t h i s v o l u m e . T h e k e r a t i n sar e o f l i t t le imp o r tan ce in ch emica l in d u st r y , b u t a r e o fi m m e n s e i m p o r t a n c e i n m e c h a n i c a l i n d u s t r y , e.g. the woollent r ad e , wh ich i s b a se d u p o n th e k er a t in co mp r ised b y sh eepwool . T he c ol lagen of th e hi d e an d skin f ibres is of v a s timp o r tan ce to ch emica l in d u st r y , an d i s th e b as is o f th eex ten siv e lea th er t r a d e s d iscu ssed in P ar ts I . to I V . T h ewaste p ieces of th es e t r ad es , to g e th er w i th b o n es , f o rm th er aw mater ia l o f th e man u f ac tu r e o f g e la t in an d g lu e , asdiscussed in P a r t V . T h e pro teid s of anim als ' f lesh andblood, milk and eggs form the source of the food proteins


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P A R T I . H I D E S F O R H E A V Y L E A T H E R

S E C T I O N L T H E R A W M A T E R I A L O FH E A V Y L E A T H E R ST H E te rm " h id e " posse sse s se ve ra l sh a d e s of m e a ni nIn i t s w ide st se nse i t a ppl ie s to the e x te rna l cove r ing a l l a n i m a l s , a n d i s s o m e t i m e s u s e d d e r o g a t i v e l y f o r h u ms k i n . I n t h i s w i d e s e n s e , i t is a l m o s t s y n o n y m o u s w it h e t e r m " s k i n . " T h e t e r m " h i d e / ' h o w e v e r , h a s n a r r o w e r m e a n i n g , i n w h i c h i t a p p l i e s o n l y t o t h e o u tcove r ing of the la rge r a n ima ls , a nd in th is se nse i s usr a t h e r i n c o n t r a s t w i t h t h e t e r m " s k i n . " T h u s w e s p eof horse h ide s , cow hide s , ca me l h ide s , a nd buffa lo h idI t i s use d in th is se nse in the t i t le of Pa r t I . o f th is volumA s s u c h h i d e s a r e f r o m l a r g e a n i m a l s , t h e l e a t h e r w h i c h m a n u f a c t u r e d t h e r e f r o m is t h i c k a n d i n l a rg e p i ec e s , ai s t h e r e fo r e c o m m e r c i a ll y d e s i g n a t e d a s " h e a v y l e a t h eF r o m t h e s t a n d p o i n t o f c h e m i c a l i n d u s t r y h i d e s a r e a m o n gt h e m o s t i m p o r t a n t o f a n i m a l p r o t e i n s , a n d t h e i r t r a nf o r m a t i o n i n t o l e a t h e r f o r b o o t s , s h o e s , b e l t i n g , s t r a ph a r n e s s , a n d b a g s c o m p r is e s t h e " h e a v y l e a t h e r t r a d ew h i c h i s o n e o f t h e l a r g e s t a n d m o s t v i t a l i n d u s t r i e s o f tc o u n t r y . T h e h e a v y l e a t h e r t r a d e p r e d o m i n a t e s o v e r o t hb r a n c h e s of le a t h e r m a n u f a c t u r e , n o t o n l y b e c a u s e of t


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8 ANIMAL PROTEINSof t h e h e a v y l e a t h e r i n d u s t r i e s . I n a v e r y n a r r o w s e ns eth e te rm is a l so so m e t im e s a p p l ie d o n ly t o o x h id e s ,w h i c h fo r m o s t h e a v y l e a t h e r s a r e t h e i d e a l r awm a t e r i a l .

T h e H o m e S u p p l y o f h id e s fo rm s a la rg e im p o r ta n tp r o p o r t i o n o f t h e t o t a l r a w m a t e r i a l . I t s i m p o r t a n c e ,m o r e o v e r , i s r a p i d l y i n c r e a s i n g , fo r t h e e x c e l le n c e a n da b u n d a n c e o f t h e h o m e s u p p l y d e t e r m i n e s t h e e x t e n t t ow h i c h i t i s n e c e s s a r y f o r t h e i n d u s t r y t o p u r c h a s e i t s r a wm a te r ia l a b ro a d . T h e p o si t io n of o u r n a t io n a l f in an cesm a k e s t h i s a n i n c r e a s i n g l y s e r io u s m a t t e r , f o r h i d e s a r ec o m p a r a t i v e l y a v e r y e x p e n s i v e m a t e r i a l .Th e q u a l i ty o f o u r h o m e su p p ly o f h id e s i s v e ry v a lu -a b l e , b e i n g d e t e r m i n e d b y t h e c o n d i t i o n s o f t h e a n i m a l ' slife, i t s p r e c i s e b r e e d , a n d b y o t h e r f a c t o r s s u c h a s a g ea n d s e x . T h e b e s t h i d e s a r e u s u a l l y o b t a i n e d f r o m a n i m a l sw h i c h h a v e b e e n m o s t e x p o s e d t o e x t r e m e s o f w i n d a n dc o l d , a s s u c h c o n d i t i o n s t e n d n a t u r a l l y t o d e v e l o p a t h i c k e ra n d m o r e c o m p a c t c o v e r in g . B r o a d l y s p e a k i n g , t h e s e

i n c l u d e t h e h i d e s f r o m c a t t l e o f t h e n o r t h e r n a n d h i l l yd is t r i c t s . Th e a g e of th e a n i m a l w h e n k i l le d i s a l so ado m ina ting fac tor . Calf skin s are ve ry soft, f ine gra ine da n d c o m p a c t , t h e s t a t e o f r a p i d g r o w t h f a v o u r i n g t h ee x i s te n c e of m u c h i n t er f ib r i ll a r s u b s t a n c e . T h e y o u n g e s ta n i m a l s s u p p l y s u i t a b l e r a w m a t e r i a l f o r v a r i o u s l i g h tl e a t h e r s ( see P a r t I I . , S e c t i o n V . , p . 1 2 0 ) , a n d a r e a l s o v e r ys u i t a b l e fo r c h r o m e w o r k ( see P a r t I I I . , S e c t i o n I I I . , p . 1 5 6 ) .B u l l a n d c o w h i d e s , o n t h e o t h e r h a n d , a r e f r o m a n i m a l sw h o s e g r o w t h i s c o m p l e t e , a n d s h o w i n c o n s e q u e n c e a l a c kof interf ibri l lar substance, coarse f ibres and a rough ando f te n w r i n k l e d g r a i n . T h e r e s u l t i n g l e a t h e r t e n d s c o n s e -q u e n t l y t o b e s p o n g y , t h i n , e m p t y a n d n o n - w a t e r p r o o f .I n t e r m e d i a t e b e t w e e n t h e s e e x t r e m e s a r e t h e h i d e s o f t h eo x a n d h e i fe r , la rg e , y e t o f g o o d te x tu re , a n d we l l su p p l ie dw i t h i n te r fi b ri ll a r s u b s t a n c e . T h e s e h i d e s a r e m u c h t h ebe st for sole lea the r , a f irm, smo oth -gr ain ed a n d well-f i lledle a th e r b e in g n e e d e d . T h e te rm " k ip " is o f te n a p p l ie dt o s m a ll h i d e s a n d t o h i d e s f r om l a r g e c a l v e s . I n t h e


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THE RAW MATERIAL OF HEAVY LEATHERS gt r a d e , h o w e v e r , " k i p " i s so m et im es u sed a lso fo r la rg eh i d e s , a s a v e r b a l e n h a n c e m e n t of v a l u e ; j u s t a s a m aw i t h a f ew o l d f ow l s i s s a i d t o k e e p " c h i c k e n s / ' C o w h i d et e n d t o b e " s p r e a d y , " i.e. t o h a v e a l a r g e a r e a p e r u n iw e i g h t , a n d a r e t h e r e f o r e m o r e s u i t a b l e f o r d r e s s i n g l e a t h e rB u l l h i d e s a r e t h i c k e r i n t h e n e c k a n d b e l l y , a n d t h i n n ei n t h e b a c k , w h i c h c h a r a c t e r i s t i c s r e d u c e t h e i r c o m m e r c i av a l u e .

M a r k e t h i d e s a r e s o ld b y w e i g h t , a n d a r e t h e r e f o rc l a s s i f i e d c h i e f l y b y t h e i r w e i g h t , w h i c h i s m a r k e d o n n e at h e t a i l b y a s y s t e m of k n i f e - c u t s . T h e a n i m a l s a r e fla yea f t e r c u t t i n g t h e h i d e d o w n t h e b e l l y a n d o n t h e i n s i dof the legs .Of t h e v a r i o u s b r e e d s , " S h o r t h o r n s " y i e l d a l a r gs u p p l y o f u s e f u l h i d e s . T h e n a m e , h o w e v e r , c o v e r s v a r i e t y o f s i m i l a r b r e e d s , a n d t h e h i d e s t h e r e f r o m a rr a t h e r v a r i a b le i n t e x t u r e a n d q u a l i t y . T h e y t e n d t o bg r e a s y o w i n g t o h i g h f e e d in g . T h e " H e r e f o r d s , " o bt a i n e d f r om M i d l a n d m a r k e t s , a r e g e n e r a l ly e x c e l l e n t h i d efo r so le an d h a rn e ss lea th e rs . T h ey g iv e a g o o d y ie ld ob u t t p e l t , a s t o u t a n d s m o o t h s h o u l d e r , a n d a r e n o t o f t eg r e a sy . " D e v o n s " y i el d a g o o d - t e x t u r e d a n d w e l l- g ro wh i d e , b u t a r e o f t e n b a d l y w a r b l e d (se e p . 1 0 ) . T h" S u s s e x " c r o ss b r e e d s y i e ld s o m e w h a t l a r g e r h i d e" S u ffo lk R e d P o l l s , " c o m m o n i n E a s t A n g l i a , y i e l d a g o ob u t t , a n d t h e c o w h i d e s m a k e g o o d d r e s s in g l e a t h e" C h a n n e l I s l a n d " c a t t l e y i e l d v e r y t h i n h i d e s , b u t w i t h fine u n d a m a g e d g r a i n . S c o t c h h i d e s p o s se s s d e s e r v e d lt h e v e r y h i g h e s t r e p u t a t i o n . T h e c l i m a t i c c o n d i t i o nf a v o u r t h e p r o d u c t i o n o f a h a r d y r a c e o f c a t t l e w i t h t h i cw e l l- g ro w n h i d e s , y i e l d i n g a l a r g e p r o p o r t i o n of b u tT h e s e h i d e s a r e a m o n g s t t h e b e s t o b t a i n a b l e f o r h e a v


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i o ANIMAL PROTEINSq u e n t l y y i e l d o f t e n a m o r e s p r e a d y h i d e . T h e W e l s h b r e e d sfo r r a t h e r s i m i l a r r e a s o n s a l so y i e l d v a l u a b l e h i d e s . T h eI r i s h " K e r r y s " a r e s m a l l b u t s t o u t , a n d y i e l d h i d e s s u i t a b l ef or l i g h t s o le l e a t h e r . I r i s h c r o s s b r e e d s , S h o r t h o r n s , h a v ea ra t h er b ad rep u t at i o n , an d are o f t en i l l f l ay ed .

A l l t h e v a r i e t i e s of t h e h o m e s u p p l y a r e s u b j e c t t ov a r i o u s d e f e c t s , w h i c h i n f l u e n c e s e r i o u s l y t h e i r c o m m e r c i a lv a l u e . O n e of t h e s e d e fe c t s is w a r b l e h o l e s o r m a r k s ,c a u s e d b y t h e O x W a r b l e f l y (Hypoderma bovis). Th i s i sa t w o - w i n g e d fly a b o u t h a lf a n i n c h l o n g . T h e l a r v a oft h i s fly , t h e " W a r b l e m a g g o t / ' l iv e s a n d t h r i v e s i n t h e s k i nof c a t t l e , a n d c au ses a so re a n d swel li n g . T h e l i fe-h i s t o ryo f t h i s i n sec t i s s t i l l i n d i sp u t e , b u t i t i s g en eral l y t h o u g h tt h a t t h e e g g s a r e l a i d i n t h e h a i r o n t h e a n i m a l ' s b a c k ,a n d t h e y o u n g l a r v a e a t s i t s w a y t h r o u g h t h e h i d e u n t i lj u s t b el ow t h e d e r m i s , a n d t h e r e f e ed s u n t i l m a t u r e . I tt h e n c r e e p s o u t of t h i s " w a r b l e h o l e , " fa ll s t o t h e g r o u n d ,p u p a t e s fo r a m o n t h , a fte r- w h i c h t h e i m a g o o r p e r f e c ti n s e c t e m e r g e s f ro m t h e c h r y s a l i s . H i d e s w h i c h h a v e b e e nt h u s i n f e c t e d h a v e , i n c o n s e q u e n c e , o f t e n q u i t e a n u m b e r o fh o l e s t h r o u g h t h e m o s t v a l u a b l e p a r t o f t h e h i d e , t h e r e b yr e n d e r i n g i t u n s u i t a b l e f or m a n y k i n d s of l e a t h e r . E v e no l d " w a r b l e s " w h i c h h a v e m o r e o r l e s s h e a l e d u p a r e aw e a k n e s s , a n d w a r b l e d h i d e s a n d l e a t h e r f e t c h a d e c i d e d l yl o w e r p r ic e t h a n u n d a m a g e d . A n o t h e r of t h e s e d e fe c t s i sb a d f laying. Clearly th e hi de sho uld be as l i t t le c ut asp o s s i b l e , b u t m a n y o f o u r m a r k e t h i d e s a r e a b o m i n a b l yg a sh e d an d o f t en c u t rig ht t h ro u g h . Th i s , of c o u rse , o f t enr e d u c e s s e r io u s l y t h e c o m m e r c i a l v a l u e of t h e h i d e . C a r e le s st r e a t m e n t a ft e r fla yin g a l s o r e s u l t s i n a n o t h e r c o m m o nd e f e c t , v i z . t a i n t . A s t h e t e r m i m p l i e s , t h e h i d e i s p a r t l yp u t r e f ie d , s o m e t i m e s o n l y i n p a t c h e s , b u t s o m e t i m e sa l s o s o e x t e n s i v e l y a s t o r e n d e r t h e h i d e q u i t e r o t t e n a n dq u i t e i n c a p a b l e of b e i n g m a d e i n t o l e a t h e r a t a l l . H i d e sa r e of c o u r s e p u t r e s c i b l e , a n d d i r t , b l o o d , d u n g a n d w a r mw e a t h e r e n c o u r a g e r a p i d p u t r e f a c t i o n . A s m a r k e t h i d e saT e u s u a l l y u n c u r e d , t h i s d e f ec t i s c o n s t a n t l y a p p e a r i n g ,a n d i s a c au s e of c o n si d erab l e l o ss . O t h e r d efec t s ar e d u e


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THE RAW MATERIAL OF HEAVY LEATHERS nto injur ies to the animal before i t i s ki l led, e.g. b r a n d s ,s c r a t c h e s d u e t o h e d g e s a n d b a r b e d w i r e , o l d s c a b s , g o a da n d t a r m a r k s . A l l t h e s e r e d u c e t h e v a l u e of t h e h i d e .Al l th e defec ts in hides invo lve a ver y ser io us loss tot h e c o m m u n i t y , a n d t h e t i m e i s r a p i d l y a p p r o a c h i n g w h e nt he i r c on t i nua n c e i s i nsuff e r abl e . T he l oss i s n o t us ua l l yv e r y c o n s i d e r a b l e t o a n y i n d i v i d u a l , t h o u g h v e r y l a r g e i n t h ea gg r e ga t e . T he h i d e i s a m inoT p a r t of t h e b e a s t ' s va l ue ,a n d a s o m e w h a t d a m a g e d h id e d o es n o t i n v o l v e a v e r ys e ri o u s lo s s t o t h e f a r m e r . S o m e w i t h t y p i c a l s t u p i d i t yr e g a r d a f e w w a r b l e s a s " t h e s i g n o f a h e a l t h y b e a s t . "Th e se de f e c t s i nv ol ve pr a c t i c a l l y n o loss t o t h e h i dem e r c h a n t , t a n n e r o r c u r r i e r , a s e a c h p a y s l e s s f o r d a m a g e dm a t e r i a l . T h e l os s f al ls u p o n t h e c o m m u n i t y , a n d t h e t i m ei s r i pe f or t he com m uni t y t o i ns i s t upon t he e l i m i na t i on oft he s e de f e c t s . Th e na t i o na l r e sou r c e s wi ll be f or som ey e a r s s t r a i n e d t o t h e i r u t t e r m o s t , a n d p r e v e n t a b l e d a m a g em u s t b e c o n s i d e re d i n t o l e r a b l e . T h e p r i n c i p a l d e f e c t s i nh i d e s a r e p r e v e n t a b l e , a n d o u g h t t o b e p r e v e n t e d . T h ewarble f ly could, by a uni ted effor t , be rendered before longp r a c t i c a l l y e x t i n c t , a t a s k w h i c h i s f a c i l i t a t e d b y t h e f a c tt h a t i t i s n o t m i gr a t i ve . B a d fla ying a n d c a r e l e ss t r e a t -m e nt of h i de s r e sul t i ng i n put r e f a c t i on a r e s t i l l m or e e a s i l yr e m e d i e d . T h e c o m m u n a l s l a u g h t e r - h o u s e i s l o n g o v e r d u ef r o m t h e s t a n d p o i n t o f p u b l i c h e a l t h , a n d w o u l d , u n d e rc o n d i t io n s of c l ea n li n es s a n d s k i l le d w o r k m a n s h i p a n dove r s i gh t , a l so so lve t h e pr ob l e m of il l- fl aye d a n d t a i n t e dh i d e s .

Th e que s t i on of t h e r a w m a t e r i a l i s of firs t i m po r t a nc et o t h e l e a t h e r t r a d e s . T h e r e w a s , b e fo r e t h e c o m m e n c e m e n to f t h e E u r o p e a n W a r , a s t e a d i l y i n c r e a s i n g s c a r c i t y o f h i d e s ,c a u s i n g a c o n s t a n t i n c r e a s e i n t h e i r p r i c e . T h i s w a s d u ep a r t l y t o t h e f a c t t h a t c a t t l e w e r e i n c r e a s i n g a t a l e s s r a t et h a n t h e p o p u l a t i o n , p a r t l y t o t h e g r o w t h o f c i v i l i z a t i o n ,a n d m o r e e x t e n s i v e u s e o f l e a t h e r i n p r o p o r t i o n t o t h ew o r l d 's p o p u l a t i o n , a n d p a r t l y t o t h e c o n s t a n t d i s c o v e r y


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12 ANIMAL PROTEINSs e r io u s e n o u g h . T h e t e rr i fi c s l a u g h t e r , n e c e s s a r y a t t h es a m e t i m e t o p r o v i d e t h e b e ll ig e r e n t s w i t h f o od a n d t h earmy wi th lea ther , i s bound to resul t in a ser ious cr i s i s fort h e l e a t h e r i n d u s t r i e s ; a n d i n c o n j u n c t i o n w i t h t h e c o u n t r y ' sfin an c ia l c o n d i t i o n , w il l m a k e i t a b s o l u t e l y n e c e s s a r y t h a ta l l c a r e s h o u l d b e t a k e n w i t h t h e r a w m a t e r i a l o f o n e o f o u rm o s t i m p o r t a n t i n d u s t r i e s . T h e f a r m e r w h o p a y s n o h e e dt o th e w arble fly , th e m a n who gash es th e hide in f layinga n d w h o a l lo w s t h e h i d e t o p u t r e f y , a r e e q u a l l y c r i m i n a lw i t h t h e m a n w h o t h r o w s b r e a d c r u s t s i n t o t h e d u s t b i n .

I t i s i m p o s s i b le t o f o r es e e , a s y e t , a n y t h i n g i n t h e n a t u r eo f a s a t i s f a c t o r y s o l u t i o n t o t h e p r o b l e m o f r a w m a t e r i a l ,e s p e c i a l l y i n r e s p e c t t o h e a v y l e a t h e r p r o d u c t i o n , f o r t h efood quest ion wi l l ra n k f irst in th e po pu lar min d, an d th ee a r l i e r s l a u g h t e r e n j o i n e d f o r t h e m o r e e c o n o m i c a l p r o d u c -t i o n o f m e a t w i ll s c a r c e l y t e n d t o in c r e a s e t h e p r o p o r t i o no f h e a v y h i d e s .T h e F o r e i g n S u p p l y of h ides i s a l so of grea t importance

a n d v a l u e . I n t h e c a s e of i m p o r t e d h i d e s p r e c a u t i o n s t op r e v e n t p u t r e f a c t i o n a r e e s s e n t i a l , a n d s o m e m e t h o d o f" c u r i n g " i s a l w a y s u s e d .S a l t i n g t h e h i d e s is o n e of t h e m o s t s a t i s f a c t o r y m e t h o d sf or t e m p o r a r y p r e s e r v a t i o n . T h e a c t i o n of s a l t i s h y g r o -s c o p ic , a n d m i l d ly a n t i s e p t i c . M o i s tu r e i s w i t h d r a w n f r o mt h e h i d e s , w h i c h a r e t h e n u n d e r c o n d i t i o n s n o l o n g e r f a v o u r -i n g t h e g r o w t h of b a c t e r i a . W e l l - s a lt e d h i d e s w i ll k e e p f o r

ye ars , especia l ly if qu i te c lean . A l ight sa l t i ng is a l so usefulf o r a s h o r t p r e s e r v a t i o n , a n d i s b e c o m i n g c o m m o n i n h i d em a r k e t s a n d t a n n e r ie s d u r i n g t h e s u m m e r a n d a u t u m nm o n t h s . S a l ti n g i s a m e t h o d u s e d e x t e n s i v e l y in t h eU n i t e d S t a t e s . T h e " p a c k e r h i d e s " of t h e s t o c k y a r d sa r e c a r ef u ll y a n d s y s t e m a t i c a l l y s a l t e d w i t h a b o u t 2 5per c ent , of sa l t an d s tore d in cool c e l la rs . Th e hid es ares o p i le d u p i n h e a p s , t h a t b r i n e e a s il y d r a i n s a w a y . T h eg r e a t d i s a d v a n t a g e of s a l t in g i s t h e s o - c a l le d " s a l t s t a i n s / 'T h e s e s t a i n s h a v e b e e n a s c r i b e d t o t h e i r o n i n t h e s a l t , t ot h e i r o n i n t h e b lo o d , t o c a l c i u m s u l p h a t e i n t h e s a l t , a n d


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THE RAW MATERIAL OF HEAVY LEATHERS 1b y s a l t i n g . T h e re l a t i v e i m p o r t a n c e of t h e s e fa c t o rs i s n oy e t s a t i s fa c t o r i l y d e t e rm i n e d , b u t c l e a n l i n e s s a n d p u re s at e n d t o e l i m i n a t e t h e t r o u b l e .

D r y i n g t h e h i d e s i s a le ss s a t i s fa c t o ry c u r e . T hp r i n c i p l e is s i m i l a r , v i z . re m o v a l of m o i s t u r e . D r i e d h i d eare , h o w e v e r , m u c h d r i e r t h a n s a l t e d , a n d a r e q u i t e h a ra n d h o r n y , h e n c e t h e n a m e " f lin t h i d e s . " T h e h i d e s a lsl o s e m u c h w e i g h t , a c o n s i d e r a b l e a d v a n t a g e i n r e d u c i nfre ight . T ro pic a l h id es are of ten flint-dry, a n d w he rp re s e rv a t i v e s a re e x p e n s i v e o r u n p ro c u ra b l e , i t i s o f t e n t ho n l y p r a c t ic a b l e m e t h o d of c u r e . N e v e r t h e l e s s , t h e m e t h oh a s m a n y s e r i o u s d i s a d v a n t a g e s , a n d i s d i f f i c u l t t o e x e c u t eI f d r i e d t o o s l o wl y t h e h i d e s p u t re fy p a r t i a l l y ; i f t o o q u i c k lt h e y d r y o n t h e o u t s i d e , a n d t h e i n t e r i o r i s l e f t t o p u t r e f yT h e f a c t t h a t h i d e s a r e o f u n e v e n t h i c k n e s s , a n d t h e c l i m a toften hot , increases the di ff icul ty , and of ten resul ts ip a r t i a l d e s t ru c t i o n o f t h e f i b ro u s s t ru c t u re o f t h e h i d eW h e n d r i e d , m o re o v e r , t h e h i d e s a r e s t il l s u b j e c t t o t ha t t a c k s of i n s e c t l arv ae , fo r t h e p re v e n t i o n of w h i c h t hu s u a l s p r i n k l i n g o f n a p h t h a l e n e o r a rs e n i c i s o n l y a n i m p e rfec t re m e d y . Th i s m e t h o d of c u re is a l so a n u i s a n c e t o t ht a n n e r , w h o h a s t o e m p l o y l a b o u r , p i t s a n d t i m e i n a t t e m pi n g t o re s t o re t h e h i d e s t o t h e i r o r i g i n a l c o n d i t i o n , a n d o f t elo s es u p t o t e n p e r c e n t , of t h e g o o d s i n s o d o i n g . D r i eh i d e s a re a l s o s u b j e c t t o t h e p re s e n c e o f a n t h ra x .D r y S a l t i n g t h e h i d e s i s a n e x c e l le n t m e t h o d of c u r i n gA s t h e n a m e im p l ie s , i t c o m b i n e s m e t h o d s of d r y i n g a ns a l ti n g w h i c h a r e u s e d a l t e r n a t i v e l y . T h e m e t h o d i s u s ee x t e n s i v e ly i n S o u t h A m e ri c a . A m o d i f ie d fo rm of i t ia ls o u s e d fo r p r e s e r v i n g t h e " E . I . k i p s , " w h i c h a r e c u r e dh o w e v e r , n o t w i t h c o m m o n s a l t , b u t w i t h e a r t h c o n t a i n i nu p t o 7 0 p e r c e n t , of s o d i u m s u l p h a t e . D r y - s a l t e d h i d e s a r


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14 ANIMAL PROTEINSS t e ri li zi ng t h e h id e s h a s b e en f r e q u e n t l y s u g g e s t e d

b u t n o m e t h o d h a s y e t b e e n a d v o c a t e d w h i c h d o e si n t e r f e r e e i t h e r w i t h t h e t a n n i n g p r o c e s s e s o r w i t hqu ali ty of th e f inished lea th er .H i d es f ro m t h e E u r o p e a n C o n t i n e n t , u s u a l ly w e t s a l t ea n d w ell flayed, e x h i b it m u c h t h e s a m e v a r i ab l e q u a l i ta s t h e ho m e s u p p l y , t h o se fro m h i g h l a n d d i s t r i c t s t e n ci ng t o b e t h i c k , y e t e ve n , w e ll g r o w n , t i g h t t e x t u r e d a r is m o o th g ra in e d , w h i l st t h o s e fro m l o w l a n d r e g i o n s a r

less s a ti sf a c to r y. T h u s h i d e s fro m t h e S w i ss A l p s a nvS c andinavia h a v e r a n k e d h i g h , w h i l s t t h e s p r e a d y D u t ec o w s a re t y p i c a l of a l o w la n d h i d e . I n t h e h i d e s w h i eo nc e c a m e fr om G e r m a n y t h e s am e f e a t u r e s a p p e a r . Bv a ri an h ig h la n d h i de s h a d a n e x c e l l e n t r e p u t a t i o n , w h i lt h o s e fro m B e r l i n , C o lo g ne , e t c . , t e n d e d t o b e l o n g i n s h a x xa n d n o t w e ll g r o w n . F r e n c h h i d e s a r e o f t e n i ll fla ye d, a nS p a nis h a n d P o r tu g u e s e a r e o fte n s u b j e c t t o s c r a t c h eI t a li a n h id es h a v e a v e r y g o od n a m e , b e i n g s m a ll b u t s t o ui n b u t t .T h e A m e r ic a n s u p p ly is i m p o r t a n t . S o u t h A i n e r i c ry i el d s a n e x c e l l en t c l a s s of h i d e , s a l t e d o x d r y - s a l t e d . T h ea re from an e x c e l le n t b r e e d of a n i m a l s , s l a u g h t e r e d a nflay ed w i t h e v e r y c a r e , a n d e f f ic i e n t l y c u r e d . A m oserio u s d efec t in th is c lass of h id e i s t h e " b r a n d / 1 w h i c

i s b o t h d ee p a n d la r g e a n d in t h e m o s t v a l u a b l e p a r t o f t f ch i de . O ne s id e , h o w e v e r, is u s u a ll y u n b r a n d e d , s o t h a t e a ch i d e y i el d s o n e g o o d " b e n d . " T h e s e h i d e s , e.g. " F r i g o rfic s," h a v e r e c e n t l y b e e n m u c h m o r e e x t e n s i v e l y t a n n e d IB r i ta in b ec a u se of t h e sh o r ta g e i n t h e h o m e s u p p l y of m a r kh id es c a used b y t h e E u r o p e a n W a r . S o u t h A m e r i c a a ly ie ld s go od h o rs e h i d e s . N o r t h A m e r i c a n h i d es a r e u s u a lwet- sa l ted (e.g. p a c k e r h id es ) . T h e y a r e u s u a ll y g o oC e n t r a l A m e r i c a y i e l d s m o s t l y d r i e d h i d e s e x h i b i t i n g t i iusual defects .


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THE RAW MATERIAL OF HEAVY LEATHERS 1a n d als o t h e d r y - s a l te d " E . I . k i p s / ' o b t a i n e d fr o m a s m ab r e e d o f I n d i a n c a t t l e , a n d e x t e n s i v e l y m a d e i n t o u p pl e a t h e r . T h e A s i a t i c h u m p e d c a t t l e a l s o p r o v i d e a l i m i t es u p p l y . T h e A f ri c a n s u p p l y is of i n c r e a s i n g i m p o r t a n cT h e t r o p i c a l p a r t s y i e l d d r i e d h i d e s o f u n c e r t a i n q u a l i tb u t t h e m o r e t e m p e r a t e p a r t s of S o u t h A fr ic a y i e l d a g r o w i nsupply of good quali t}?.

REFERENCES.*' The M anufacture of L eather " (Bennett), pp . 27-37." Principles of L eather M anufacture " (Proc ter), p p. 33-56." The Ox Warble or Bot Fly " (E . Ormerod)." The M aking of L eather " (Procter), pp. 2-22.


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S E C T I O N I I . T H E P R E P A R A T I O N O F P E L TB E F O R E h i d e s a r e t a n n e d i t i s n e c e s s a r y f o r t h e m t o p a s st h r o u g h a s e r ie s of p r e p a r a t o r y p r o c e s s e s . T h e o b j e c t oft h e s e p r o c e s s e s i s t o o b t a i n f r o m t h e h i d e t h e t r u e h i d es u b s t a n c e i n a p u r e a n d s u i t a b le c o n d i t i o n . E a c h c l a s s ofl e a t h e r h a s i t s o w n a p p r o p r i a t e p r o c e s se s , t h e a d j u s t m e n tof w hic h larg ely dete rm ines th e qua l i ty of th e f inisheda r t i c l e . S o p r o m i n e n t i s t h e i nf lu e n c e of t h e s e p r e p a r a t o r ym e t h o d s t h a t t h e p a r a d o x " g o o d l e a t h e r i s m a d e b e f o r et a n n i n g " i s i n t r a d e c ir c le s a l m o s t a p l a t i t u d e . T h e s ep r o c e s s es , s o m e t i m e s l u m p e d t o g e t h e r u n d e r t h e g e n e r a ln a m e of " W e t w o r k / ' c o m p r is e s o a k i n g , l im i n g , b e a mhou se w ork an d del im ing. These wil l be discu ssed int u r n .

T h e t e r m a p p l i e d t o t h e h i d e a f t e r t h e s e p r o c e s s e s , b u tb e f o r e t a n n a g e , i s " p e l t . "S o a k i n g h a s fo r i t s o b je c t t h e c l e a n s in g a n d s o ft e ni n gof t h e h i d e s , c h i e fl y b y m e a n s of w a t e r . I t a i m s a t t h er e m o v a l o f d i r t , b l o o d , d u n g , a n d c u r i n g m a t e r i a l s b yw a s h i n g . T h e p r o c e s s i s u s u a l l y s i m p l e , a n d i s m u c h t h esa m e for a l l c lasses of leathe r . Th e ideal to be a im ed at

i s t o r e s t o r e t h e h i d e t o i t s c o n d i t i o n w h e n i t l ef t t h e a n i m a l ' sb a c k . C l e a n li n e ss i n l e a t h e r m a n u f a c t u r e i s a s e s s e n t i a la t t h e c o m m e n c e m e n t a s a n y w h e r e , f o r t h e h i d e i s i n i t sm o s t p u t r e s c i b l e s t a t e . T h e s o lu b le p r o t e i d s ( b l o o d, l y m p h ,p a r t of du ng , e tc . ) whic h a lwa ys "adhere to hide s en-c o u r a g e t h e r a p i d g r o w t h o f p u t r e f a c t i v e b a c t e r i a , a n dc a n n o t b e w a s h e d a w a y t o o s o o n . D u n g i s o f t e n d if fi c u ltt o r e m o v e , b e i n g c a k e d o n t h e b u t t e n d a m o n g s t t h e h a i r .So a k i n g o n l y s o f t e n s i t , a n d m e c h a n i c a l r e m o v a l i s u s u a l l yn e c e s s a r y . I f s u c h s u b s t a n c e s a r e n o t r e m o v e d , t h e y g o


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THE PREPARATION OF PELT 17f D i " " v v a r d w i t h t h e g o od s i n t o t h e l im e l iq u o r s , c a u s in g s t a i n sS o f l i id e s u b s t a n c e , a n d c o u n t e r a c t in g p l u m p i n g .d e t a i le d m e t h o d a n d t i m e of s o a k i n g a r e d e t e r m i n e db y t h e n a t u r e of t h e c u r e . O n e of t h e p u r p o s e s os o a k l iq u o r s i s t o d i ss ol ve t h e s a lt u s e d in c u r i n g h i d e- t o r e h y d r a t e t h e h i d e a n d m a k e i t a g a i n so ft a n d p l i a b lex o - p e r - c e n t . s a l t s o l u t i o n e x e r t s a s o l v e n t e f f e c t o n h i d

, i t is necessary soon to change the f i l rs t soak l iquoo f 3 a J L t : e d g oo ds.^ M t h id e s , w h ic h a r e u nc u re d, r e q u ir e t h e le a st h e c l e a n s i n g e ffe c t b e i n g m o s t n e e d e d . T ha , r e i n s e r t e d i n t o p i t s ( " w a t e r d y k e s " ) of w a t e r f of e w h o u r s , a n d t h e w a t er c h a n g ed o nc e o r t w ic e . T hk s h o u l d n o t b e p r o l o n g e d a s t h e h i d e s a r e s o p u t r e, a n d w h e r e i t i s c u s t o m a r y t o l e a v e t h e g o o d s i n l i q u o r o v e r n i g h t , i t is a d v a n t a g e o u s t o a d d a l i tt l e sl a kel i m e - t o t h e w a t e r b efo re i n se r ti n g t h e g o o ds . T h i s n o t o nls o f " t e r x s h a r d w a t e r , b u t is m i ld ly a n t i se p t ic a n d p l u m p i n ga x x d f o x m s a s u i ta b l e i n t r o d u c t i o n t o t h e l im i n g p r o p e rJ v a o J h . p i t c o n t a in s a " p a c k " of 3 0 -5 0 h id e s, a c c o rd in g ti t s c a p a c i t y , w h i c h v a ri es in different t a n n e r ie s fro m 100t o 3 0 0 0 g allo ns . T a i n t e d g oo ds, w h ic h a r e i nd ic a te d ba o l i s t x a c t e r i s t i c w h i t e c o lo ur o n t h e flesh s id e a n d b y lo osh a . i x , n e e d a p r e li m i n ar y w a s hi ng e i t h er in a " d r u m ,t u m b l e r " o r in a " p a d d l e . " T h i s e n s u r e s a r a p ic h a x x g e of l iq uo r a n d t h e r em o v a l of m o s t of t h e p u t r ef a c t i v e a ge nc ie s . B a d c a se s m a y n ee d t h e a pp lic a t io n oa n t i s e p t i c s , su c h a s im m e rs io n in 0 1 p er c e n t, c a rb o lia c i d ; b u t if p o ss ib le t h e s e s h o u ld b e a v o i d e d , a s t h e


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18 ANIMAL PROTEINSd r u m or p a d d l e b e fo re p i t s o a k in g is e x t r e m e l y u s e f u l effec t t h e r a p i d r e m o v a l of s u p e r fi c i a l s a l t , a n d i s a lu s ef ul a f te r p i t s o a H n g t o r e m o v e t h e l a s t t r a c e s .

D r ie d a n d d r y - sa l te d go od s n e e d a s o a k i n g s ti ll m op r ol o ng e d , u p t o o n e w e e k if w a t e r a l on e b e u s e d . W it h e a s s i s t a n c e o f c a u s t i c s o d a , h o w e v e r , t h e p r o c e s s c a n . fs h o r te n e d t o a b o u t t w o d a y s . T h e fixst s o a k l i q u o r s h o uc o n s i st of a o *i p e r c e n t , s o l u t i o n of c a u s t i c s o d a , a n d a f tt h e g oo ds h a v e b e e n i n se r te d t w e n t y - f o u r h o u r s , t h e y wb e m a t e ri a ll y i m p r o v e d b y a fe w h o u r s ' d r u m m i n g p a d d li n g . A n o t h e r c a u s ti c s od a s o a k w i ll c o m p l e t e tp ro c es s. S o d iu m s ul ph id e c r y s ta ls m a y r e p l a c e c a u ss od a, b u t a b o u t t h r e e t i m e s t h e w e i g h t w i l l b e n e e d eC a r b on a te of s o d a a n d c a u s t i c l im e a ls o a r e a c o n v e n i ec o m m e rc i a l s u b s t i t u t e fo r c a u s t ic s o d a . F o r 1 0 l b s . c a u ss o d a , u se 36 l b s . c a r b o n a t e a n d 7 l b s . l i m e . E x t r a l i ms ho u ld b e a d d e d i n a ll c a s es w h e n t h e w a t e r i s h a r d . A cl iq u o r s w i ll a ls o s o ft e n d r i e d a n d d r y - s a l t e d g o o d s , t rs u c h p ro c e ss es d o n o t fit i n s o w e ll w i t h t h e s u b s e q u el im i n g. T h e u se of p u t r i d s o a k s a n d s t o c k s m a y h e n oconsidered out of da te .L i m i n g fo llo ws s o a k in g , a n d c o n s i s t s e s s e n t i a l l y i m m e r s i n g t h e h i d e s f or 7 - 1 0 d a y s i n m i l k o f l i m e . T hc h ief o b j e c t i n v i ew i s t o l oo s en t h e h a i r a n d p r e p a r e fi t s m e c h a n i c a l r e m o v a l . L i m i n g t a k e s p l a c e i n p i t s , t lt o p s of w h i c h a r e l e ve l w i t h t h e l i m e y a r d flo or. T h e l i mis s la k ed c o m p l e te ly a n d m i x e d w e ll w i t h w a t e r i n t h e p ib e in g p a r t i c u l a r l y w e ll p l u n g e d j u s t b e f o re t l i e i n s e r t i oof a p a c k of g o o d s. S a t u r a t e d H m e w a t e r is o n l y a 0 * 1p e r -c e n t . s o l ut io n . T h e g oo ds a r e o c c a s i o n a l ly " h a n d l e di.e. h a u l ed o u t of t h e p i t a n d r e i n s e r t e d a f t e r p l u n g i n( " h a u l i n g " a n d u s e t t i n g " ) . T h is is n e c e s s a r y t o k e et h e li qu o r s a t u r a t ed w i t h l im e . T h e h i d e s a r e i n s e r ton e b y o n e, e a c h b ei ng " p o k e d d o w n " t o e n s u r e i t s c o n t aw i t h t h e l i q u o r . T h e g o o d s a re i n v a r i a b l y i m m e r s e d fixi n a p r ev i o us ly u s e d l im e l iq u o r . M o st t a n n e r i e s n o w c a r


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THE PREPARATION OF PELT 19l a b o r i o u s t o c a r r y o u t t h e w h o l e p r o c e s s i n o n e p i t . I n t h i s" o n e - p i t s y s t e m " t h e g o o d s a r e - i n s e r t e d f o r ( s ay ) f o u rda ys i n a n o l d use d l im e l i quor , w i t h oc c a s i ona l h a n dl i n g ;t h i s l i q u o r i s t h e n r u n t o t h e d r a i n a n d a n e w l i q u o r m a d eu p i n t h e s a m e p i t , i n t o w h i c h t h e g o o d s a r e in s e r t e d f or( s ay ) fiv e d a y s . T h e y a re t h e n h a u l e d a n d s e n t t o t h eu n h a i r e r s . E a c h p a c k t h u s g e t s t w o l i q u o r s , o l d a n d n e w .

A b e t t e r m e t h o d is t h e " t h r e e - p i t s y s t e m / ' I n t h i sc a s e e a c h p a c k re c e i v e s t h r e e l iq u o r s a n d h a s ( s a y) t h r e ed a y s i n e a c h , f irst a n " o ld l i m e , " t h e n a " m e d i u m l i m e / ' a n dfinally a " n e w l i m e . " Th i s sys t e m e ns ur e s a gr e a t e r r e gu -l a r i t y o f t r e a t m e n t , a n d i s d e s e r v e d l y t h e m o s t p o p u l a rm e t h o d f or l i m i ng h i de s f or so le l e a t h e r . Af t e r be i n g use do n c e a s a " n e w li m e , " a l iq u o r t h e n b e c o m e s a " m e d i u ml i m e , " a n d a f t e r b e i n g t h u s u s e d b e c o m e s t h e " ol d l i m e "w h i c h r e c e i v e s t h e g r e e n h i d e s f ro m t h e s o a k s . T h es y s t e m i n v o l v e s t h e g o o d s b e i n g s h i f t e d t w i c e t o a n o t h e rp i t , w h i c h i s m o r e l a b o r i o u s t h a n r e i n s e r t i o n i n t o t h e o l dpi t , but i f t he l i m e ya r d be a r r a nge d i n " se t s " or " r ounds "of t h r e e p i t s , t h e sh if t is usu a l l y on l y t o t h e a d j a c e n t p i t .O n e s p e c i a l a d v a n t a g e of t h i s s y s t e m is t h a t t h e t o p h i d e si n o n e p i t b e c o m e t h e b o t t o m h i d e s in t h e n e x t p i t , a n d viceversa. R o u n d s o f m o r e t h a n t h r e e p i t s a r e s o m e t i m e s u s e d .M a n y f a c t o ri es h a v e n o w a d o p t e d s y s t e m s in w h i c ht h e r e i s no ha n dl i ng a t a ll . Th e h i de s a r e su sp e n de d i n l i m e

l i q u o r s w h i c h a r e a g i t a t e d b y m e c h a n i c a l c o n t r i v a n c e s (e.g.T i l s to n - M e l b o u r n e p r o c e s s ) , o r b y j e t s of c o m p r e s s e d a ir(e.g. F o r s a r e p r o c e s s ) . T h e g o o d s a r e s o a k e d a n d l i m e d" m e l l o w t o f r e s h " b y c h a n g i n g t h e l i q u o r s b y m e a n s o fp u m p s , a i r e j ec t o r s , e t c . T h u s t h e h i d e s n e e d n o l a b o u rfrom f i rs t being inser ted unt i l drawn for depi la t ion.I n l i m i ng, t he whol e of t he e pi de r m i s a s we l l a s t heha i r is l oosene d, a n d i s su bse qu e nt l y r e m ov e d i n d e p i l a t i on .

T h e c o r i u m o r t r u e h id e s u b s t a n c e b e c o m e s m u c h m o r es w o l l e n b y i m b i b a t i o n o f w a t e r , a n d w h e n t a k e n o u t o ft h e n e w li m e i s " p l u m p e d " t o v e r y f irm j e l l y . T h i s


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20 ANIMAL PROTEINSc o n s t i tu en t f ib rils , wh ic h f ac t ass is ts v e r y m ate r ia l ly in o b ta in -in g a q u ick an d c o m p lete ta n n ag e, g o o d w eig h t , an d a firml e a t h e r . D u r i n g t h e l i m i n g , t h e n a t u r a l g r e a se of t h e h i d eis saponif ied or emulsif ied, which prepares for i ts removali n s c u d d i n g . L i m i n g is t h u s a c o m p l e x p r o c e s s : t h e h a i r i slo osen ed, th e h id e i s p l u m p e d , an d t h e g r ease i s " k i l led ."A l l t h e s e r e s u l ts m a y b e h a s t e n e d b y t h e u s e of o t h e ra l k a l i e s i n a d d i t i o n , a n d m o s t h e a v y l e a t h e r y a r d s a s s i s tth e l imin g b y ad d in g a lso so d iu m su lp h id e o r c au st i c so d ao r b o th . S o d iu m su lp h id e i s a p o wer f u l d e p i la tan t , an d wi l la lo n e u n h air h id e s eas i ly in s t r o n g so lu t io n s ev e n in a f ewh o u r s . A s i n s o l u t i o n i t f o r m s c a u s t i c s o d a b y h y d r o l y s i s ,i t p o ssesses a lso th e p o wer f u l p lu mp in g an d sap o n if y in gp o wer s c h ar ac ter is t i c of th e la t te r . Th e ad d i t io n of a r sen icsulphide (As2S 2) ( r ea lg ar) t o th e l ime w h e n s lak in g c au sest h e p r e s e n c e o f c a l c i u m s u l p h y d r a t e i n t h e l i m e l i q u o r s t h u sm a d e . T h i s is a l s o a p o w e r f u l d e p i l a t a n t , b u t n o t m u c hu sed f o r h eav y lea th er .

Th e f u n ct io n o f th e l im e in d ep i la t in g i s c o m p lex an dh a s o c c a s io ne d m u c h d i s c u s s io n . I t s m a i n p u r p o s e , h o w -e v e r, i s t h a t of a p a r t i a l a n t i s e p t i c . W h e n h i d e s p u t r e f y ,o n e of th e f irs t r esu l ts i s t h a t th e h a i r i s lo o sen ed . I nA m e r ic a d e p i l a t i o n b y " s w e a t i n g " i s c a r r ie d o u t c o m -m e r c i a l l y b y s u c h a m i l d p u t r e f a c t i o n , t h e l i m e l i q u o rp er mits a s imi lar f er men ta t io n a t a s lo wer r a te , an d a l lt a n n e r y l i m e l i q u o r s a r e s w a r m i n g w i t h p u t r e f a c t i v e b a c t e r i a ,l a m i n g i s t h u s a s af er m e t h o d t h a n s w e a t i n g , w h i c h m a y b eeasi ly car r ied to o f ar . Var io u s wo r k er s h av e i so la tedspec ific o r g an ism s W o o d a bacillus, S c h m i t z - D u m o n t astreptococcus b ut i t s e e m s h i g h l y p r o b a b l e t h a t t h el i m e y a r d b a c t e r i a a r e j u s t t h e c o m m o n o r g a n i s m s o f p u t r e -f a c t i o n s o r t e d o u t o r s e l e c t e d b y t h e e x a c t n a t u r e o f t h el i q u o r a n d t h e m e t h o d of w o r k i n g t h e l i m e s . M a n y p u t r e -f a c t i v e b a c t e r i a a r e v e r y a d a p t a b l e a n d c o u l d e a s i l y a c -


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THE PREPARATION OF PELT 21l i m e y a r d w i l l d e p e n d u p o n t h e a m o u n t a n d n a t u r e o f t h ed i s so l v e d o r g a n i c m a t t e r a v a i l a b l e a s f o o d , a n d u p o n t h ee x a c t a l k a l i n i t y a n d t h e c o n c e n t r a t i o n o f o t h e r a p p a r e n t l yi n e r t s u b t a n c e s , s u c h a s c o m m o n s a l t a n d s o d i u m , c a l c i u ma n d a r s e n i c s a l t s . H e n c e n o t w o l im e l i q u o r s o p e r a t e a l i k e ,a n d a p p r o x i m a t e r e g u l a r i t y i s o n l y a s s u r e d b y s y s t e m a t i cm e t h o d . I n h a n d l i n g a n d s h i f t i n g , t h e o r g a n i s m s a r es u b j e c t e d t o f u r t h e r s e le c t i o n , a n d t h e m o s t a d a p t a b l es u r v i v e . I t i s p r o b a b l e t h a t d i ff er e nt s p e c i e s m a y a c ts y m b i o t i c a l l y . T h e d e p i l a t i n g o r g a n i s m s of l i m e l iq u o r sa r e p r o b a b l y m o s t l y a n a e ro b e s , b u t s o m e m a y b e a n a e ro b i cb y a d a p t a t i o n . I t i s p r o b a b l e t h a t ae ro bic f e r m e n t s c o m -m e n c e t h e d e p i l a t i o n , b u t t h i s w i l l b e d o n e b e f o r e t h e g o o d sa r e p u t i n t o w o r k , o r a t a n y r a t e b e fo r e t h e y r e a c h t h el imes . M o re s t r i c t l y , i t i s t h e e n z y m e s s e c r e t e d b y b a c t e r i aw h i c h a r e d i r e c t l y r e s p o n s i b l e f o r t h e h y d r o l y t i c w o r k ;t h e s e e n z y m e s a re c h ie fly p r o t e o l y t i c ( p r o t e i d s p l i t t i n g ) ,b u t t h e l i p o l y t i c ( f a t s p l i t t i n g ) e n z y m e s h a v e a l s o a p l a c e .

T h e l i m e , h o w e v e r , n o t o n l y l i m i t s a n d s e l e c t s t h ecourse of the put refac t ion, but a lso af fords more posi t ivea s s is t a n c e . L i m e p l a y s i t s o w n h y d r o l y t i c p a r t a n d a s s is t st h e d ep i la t io n b y p u r e l y c h e m i c a l a c t i o n . L i m e w i ll u n h a i rw i t h o u t t h e a s s i s t a n c e o f b a c t e r i a , b u t i t s a c t i o n i s s l o w a n df o rm s a m i n o r p a r t of t h e o p e r a t i o n i n t h e a v e r a g e l i m e y a r d .This ac t ion i s due chief ly to i t s progressive format ion ofc a l c i u m s u l p h y d r a t e f r o m t h e c y s t i n e g r o u p of t h e s o ft e rk e r a t i n s . L i m e a l so p l a y s a n e s s e n t i a l p a r t i n a s s i s ti n gt h e p u t r e f a c t i v e f e r m e n t a t i o n . I t s o f te n s t h e k e r a t i n sa n d t h u s a s s i st s t h e b a c t e r i a l a t t a c k , i t h y d r o l y z e s o t h e rp r o t e i d s a n d p r o v i d e s t h e b a c t e r i a w i t h f o o d i n s o l u t i o n ,t h e c a l c i u m i o n in c r e a s e s t h e p r o t e o l y t i c a c t i o n of c e r t a i ne n z y m e s , a n d fin ally t h e a p p a r e n t l y i n e r t e x c e s s o f u n -d i s s o l v e d l i m e h a s a n a c c e l e r a t i n g e f f e c t o n t h e b a c t e r i a la c t i v i t y .

I n t h e a v e r a g e l i m e y a r d t h e s e v a r i o u s f u n c t i o n s a r ei n e x t r i c a b l y m i x e d u p , a n d i t i s i m p o s s i b l e t o a s s i g n a n y


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22 ANIMAL PROTEINSw i l l u n h a i r , a n d s u l p h i d e s w i l l a l s o u n h a i r w i t h o u t l i m e o rb a c t e r i a , b u t i n t h e l i m e y a r d a l l t h r e e a g e n c i e s a r e a t w o r k .P u t r e f a c t i v e f e r m e n t a t i o n , h o w e v e r , o b t a i n s a g o o d s t a r t .^ E r o b ic f e r m e n t a t i o n c o m m e n c e s w i t h t h e s l a u g h t e r of t h ea n i m a l , a n d t h e a n a e r o b i c o r g a n i s m s s o o n c o m m e n c e t h e i rp a r t , a n d a r e a t w o r k i n t h e h i d e h o u s e a n d s o a k s . O ne n t e r i n g t h e l i m e s , t h e p u r e l y c h e m i c a l h y d r o l y t i c a c t i o no f l i m e i s a d d e d t o t h a t o f t h e b a c t e r i a l e n z y m e s a s w e l la s t h e a c t i o n of l i m e a s b a c t e r i a l a s s i s t a n t , a n d t h e t h r e ec o n t i n u e t o o p e r a t e s id e b y s i d e . E a c h g i v es r i se t o t h ef o r m a t i o n o f c a l c i u m s u l p h y d r a t e , w h o s e o w n s p e c i a lso lvent effec t is sup era dd ed . I f su lp hyd rates be del ibe rate lya d d e d t o t h e l i q u o r s t h e r e i s y e t a n o t h e r f a c t o r a s s i s t i n g .S p e a k i n g b r o a d l y , t h e b a c t e r i a l e n z y m e s h a v e t h e i r m a x i -m u m a c t i v i t y i n t h e o l d l i m e s , a n d t h e c h e m i c a l a c t i o n o fs u l p h y d x a t e f o r m e d f r o m t h e k e r a t i n c y s t i n e i s a l s o a t am a x i m u m in t h e s e l i q u o r s . T h e c h e m i c a l a c t i o n of a d d e ds u l p h i d e , a n d t h e s i m p l e h y d r o l y t i c a c t i o n o f c a l c i u mh y d r a t e h a v e t h e i r m a x i m u m a c t i v i t y i n t h e n e w l i m e s .M o s t o b s e r v e r s w o u l d a g r e e t h a t in p r a c t i c e t h e b a c t e r i ashoulder the greater par t of the work .

F r o m t h e 4 l i m e y a r d i s t a k e n a b o u t t h e o n ly w a s t e b y e -p r o d u c t s of t h e t a n n e r y , v i z . t h e r e s id u e s f i o m t h e s o a kand lime p i t s . Th ese cons is t ma inly of l ime and ch alk , w i thsome hair and du ng, an d poss ib ly a l i t t le su lphid e . T h es ludge possesses som e va lue as a m an ure , espec ia l ly if f romt h e s o a k p i t s o n a c c o u n t of t h e g t e a t e r n i t r o g e n c o n t e n t .( P a r t V I . , S e c t i o n I . )

T h e B e a m H o u s e W o r k c o n s i s t s i n t h e m e c h a n i c a lr e m o v a l o f t h o s e p a r t s o f t h e h i d e n o t w a n t e d f o r l e a t h e rm a n u f a c t u r e . Unhairing r e m o v e s t h e h a i r a n d t h e e p i d e r -m is m ad e loose in l im ing . Th e h ides are p lac ed over as lo p in g " b e a m " w i t h a c o n v e x s u rf a c e , a n d t h e h a i rs c r a p e d off w i t h a b l u n t c o n c a v e a n d d o u b l e - h a n d le d k n i f e .T h e h i d e s a r e t h e n t h r o w n i n t o a p i t of w a t e r . T h e h a i ris carefu l ly co l lec ted , washed wel l wi th water , p referably


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THE PREPARATION OF PELT 23k e p t s e p a r a t e a n d f e t c h e s a h i g h e r p r i c e . Fleshing i s t h en e x t p ro cess . T h e h id es a r e ag ain p lac ed o v er a "beam ,with the f lesh side (i.e. th e s id e n ear es t th e f lesh ) u p p er -m o s t . S k il le d w o r k m e n t h e n c u t off, w i t h a s h a r p c o n v e xknife, the fat , flesh a n d co nn ec tiv e t issu e left in f laying.Rounding i s u s u a l l y t h e n e x t p r o c e s s . T h e u n h a i r e d a n dfleshed h id e i s sp r e ad o u t fla t an d c u t u p in to b u t t , s h o u ld era n d a p a ir of b e l li e s . T h e s e p a r t s h a v e d i ff e r en t c o m m e r c i a lv a l u e s , a n d m a y a f t e r w a r d s b e t a n n e d b y d i ff e re n t m e t h o d sf or v er y d i f fer en t p u r p o ses f o r d r es s in g lea th e r , an d so m e-t im es ev en f o r so le lea th er . Scudding i s th e las t p iece o fb e am wo r k . T h e flesh ed h id es (w h eth er r o u n d ed o r n o t ) a r ew a s h e d , o r a t l e a s t r i n s e d , w i t h w a t e r , a n d a g a i n p l a c e d o nt h e b e a m g r ai n s i d e u p . T h e y a r e t h e n s c r a p e d w i t h ar a t h e r s h a r p c o n c a v e k n i f e , t o r e m o v e " s c u d , " w h i c h c o n s i s t sof h a i r r o o ts an d sh ea th s , l im e so a p s , f a t , p ig m en t an d o th e rd i r t . S h o r t h a i r i s sh a v e d off b y a v e r y sh ar p h a n d k n i f e .

T h e b e a m w o r k d e m a n d s a c e r t a i n a m o u n t o f s k i l l f r o mth e wo r k m en , esp ec ia l ly f r o m t h e f lesh er , wh o se sh ar pk n i f e m a y p r o v e v e r y w a s t e f u l i n i n c o m p e t e n t h a n d s .H a n d l a b o u r w a s s l o w l y b u t s u r e l y b e i n g r e p l a c e d b ym a c h i n e r y b e f o r e t h e w a x , a n d w a r - t i m e c o n d i t i o n s h a v eg r e a t ly a c c e l e r a t e d t h e r a t e of t r a n s i t i o n . B e a m h o u s em a c h i n e r y i s r a p i d l y b e c o m i n g u n i v e rs a l . T h e m a c h i n e sa r e c u m b r o u s a n d e x p e n s i v e i n c o s t a n d i n p o w e r , b u tm a c h i n e w o r k i s q u ic k e r , l e s s l a b o r i o u s , a n d n e e d s m u c hfe we r w o r k m e n . M a n y t y p e s of m a c h i n e h a v e b e e n s u g -g e s te d , b u t t h e m o s t u s e fu l a r e t h o s e i n w h i c h t h e h i d e sp a s s o v e r r o ll e rs a n d a r e s i m u l t a n e o u s l y a c t e d u p o n b y ar a p i d l y r e v o l v i n g c y l i n d r i c a l k n i fe w i t h s p i r a l b l a d e s , o n eh al f b ei n g a l e f t - h a n d e d a n d t h e o t h e r a r i g h t - h a n d e d s p i r a l ,s o t h a t t h e h i d e is s c r a p e d o u t w a r d s a s w e l l a s i n t h e d i r e c t i o nof m o t i o n . T h e p a r t of t h e h i d e b e i n g a c t e d u p o n r e s t s o na p n e u m a t i c r o l l e r. B y c h a n g i n g t h e t y p e of s p i r a l k n i fecy l in d er th e m ach in e wi l l u n h ai r , f lesh o r scu d .

D e l i m i n g i s a g e n e r a l n a m e c o v e r i n g a n u m b e r ofs i m i l a r o p e r a t i o n s w h o s e p r i m a r y o b j e c t i s t h e n e u t r a l i z a t i o na n d r e m o v a l o f t h e c a u s t i c l i m e a n d s o d a i n t h e p l u m p e d


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24 ANIMAL PROTEINSp e l t , o r a t a n y ra t e o n th e s u rfa ce o f th e h id e . T h is i s ap r e p a r a t i o n f or t h e t a n l i q u o r s . A l l t h e t a n n i n s a n d m a n ya s s o c i a te d s u b s t a n c e s d a r k e n r a p i d l y w i t h o x i d a t i o n w h e nin a lk a l in e s o lu t io n , s o th a t to p la ce th e fu l ly l ime d h id ein a ta n l iq u o r w o u ld g iv e a d a rk -c o lo u re d le a t h e r . As h o r t i n s e r t i o n i n a b a t h o f w e a k a c i d w o u l d s e c u r e t h ee l imin a t io n o f s u rfa ce l ime a n d th e d is a p p e a ra n ce o f th isd if ficu lty, b u t th e re a re o th e r p u r p o s e s in d e l imin g . T h em o r e c o m p l e te l y l i m e i s r e m o v e d t h e m o r e t h e p l u m p e dp e l t " f a l l s " i n t o a s o f t , p l i a b l e , u n s w o l l e n a n d r e l a x e dc o n d i t i o n , a n d t h i s c h a n g e a s s i s t s v e r y m a t e r i a l l y i n t h ep ro d u ct io n o f a s o f t d re s s in g le a th e r , s u i ta b le fo r b o o tu p p e rs , b a g s , e tc . F o r s u ch le a th e rs , th e re fo re , th e d e l imin gm u s t b e m u c h m o r e c o m p l e t e t h a n f o r s o l e l e a t h e r , i n w h i c hth e o b je c t i s to o b ta in a fi rm a n d p l u m p le a th e r .

In th e ca s e o f th e s o f te r d re s s in g le a th e rs , e x p e r ie n cein d ica te s th e a d v is a b i l i ty o f a l lo win g s o me fu r th e r b a c te r ia la c t i o n o n t h e i n t e r fi b r i ll a r s u b s t a n c e i n o r d e r t o p r o d u c eth e re q u is i te p l ia b i l i ty a n d s o f tn e ss . T h is i s s e c u re d b y" b a t i n g " t h e h i d e s . T h i s p r o c e s s c o n s i s t s i n im m e r s i n gth e g o o d s in to a co ld fe rme n t in g in fu s io n o f h e n o r p ig e o nd u n g . T h e in fu s io n is m a d e in a s p e c ia l tu b o r p i t w i thw a r m w a t e r a n d a l lo w e d t o s t a n d f o r a d a y o r t w o u n t i lt h e f e r m e n t a t i o n h a s c o m m e n c e d , a n d t h e n r u n i n t o t h eb a t in g p i t th ro u g h a c o a rs e f il te r s u c h a s s a c k in g . T h eh id e s a re imm e rs e d fo r s o me d a y s , b u t a re h a n d le d f re -q u e n t ly to e n s u re a n e v e n e ffec t . T h e b a te is a lwa y ss l ig h t l y a l k a l i n e . T h e c a u s t i c a l k a l i n i t y in c r e a se s r a p i d l y a tf irs t owing to the diffus ion of caustic l ime, then a t a s lowerra te , a f te rwa rd s s lo wly d e c l in in g . T h is i s e x p la in e d b y th ep r o d u c t i o n o f o r g a n i c a c i d s , a n d t h e i r s a l t s w i t h w e a k b a s e sf r o m t h e d u n g i n fu s io n b y t h e a c t i o n of b a c t e r i a . T h e t o t a la lk a l in i ty of th e b a t e l iq u o r in cre a s e s ra p id ly a t f irst o w in g tothe diffus ion of l ime and i ts l iberation of organic bases , thenv e r y s l o w l y , b u t t o w a r d s t h e e n d o f t h e o p e r a t i o n t h e t o t a la lk a l in i ty in cre a s e s v e ry ra p id ly in d e e d , o win g p ro b a b ly tot h e c o m m e n c e m e n t of a v i o l e n t a n ae ro b ic f e r m e n t a t i o n w h i c hp r o d u c e s a m m o n i a a n d o t h e r o r g a n i c b a s e s , a n d w h i c h


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THE PREPARATION OF PELT 2 5h e r a l d s t h e a p p r o a c h o f a p u t r e f a c t i v e a c t i o n , w h i c h i fa l lo w e d t o c o n t i n u e f or e v e n a s h o r t t i m e w i ll r u i n t h eh i d e s . B a t i n g i s c o n s e q u e n t l y a r i s k y p r o c e s s , a n d n e e d se x p e r i e n c e d o v e r s i g h t . F o r g o o d s w h i c h n e e d o n l y a m i l db a t i n g , t h e r e i s t h e a l t e r n a t i v e o f g i v i n g a l o n g e r l i m i n g i no ld e r l i m e s . T h i s of c o u r s e i n v o l v e s m o r e b a c t e r i a lh y d r o l y s i s , a n d p e r h a p s d o e s i t in a s a fe r , m o r e e c o n o m i c a lan d c er ta in ly in a . less offensive m an ne r . B at in g is of tenf o ll ow e d b y a f u r t h e r d e l i m i n g b y a c i d s . B o r i c , l a c t i c ,a c e t i c , f o rm i c a n d b u t y r i c a c i d s a r e a l l u s e d , a n d w i t h c a r ee v e n h y d r o c h l o r i c a n d s u l p h u r i c a c i d s m a y b e e m p l o y e d .I n n u m e r a b l e " a r ti fi c i a l " b a t e s h a v e b e e n p u t o n t h e m a r k e t ,b u t m o s t a r e m e r e l y w e a k a c i d s , a c i d s a l t s o r s a l t s o f s t r o n ga c i d s w i t h w e a k b a s e s . A n A m e r i c a n " b a c t e r i a l b a t e "c o n s i s t s o f a l a c t i c f e r m e n t a t i o n o f g l u c o s e i n t h e p r e s e n c eof glue.

C lo se ly s i m i l a r t o b a t i n g is " p u e r i n g , " i n v e s t i g a t e d b yWood (see p . 94) .D r e n c h i n g i s a n o t h e r f e r m e n t i v e d e l i m i n g p r o c e s s . I nt h i s t h e g o o d s a r e i n s e r t e d i n t o a n i n f u si o n of b r a n . T h i si s m a d e b y s c a l d i n g t h e b r a n w i t h h o t w a t e r , a n d a l l o w i n git to s ta nd un ti l i t is ab o u t 7O~9O F . T he infusion is t h e n" i n o c u l a t e d " w i t h a f ew g a l lo n s of o l d d r e n c h l i q u o r ,a n d t h e g o o d s a r e i m m e r s e d . T h i s f e r m e n t a t i o n h a s b e e ne x a m i n e d c a re f ul ly b y J . T . W o o d . F i r s t t h e e n z y m ec e r e a l i n c o n v e r t s b r a n s t a r c h i n t o g l u c o s e , w h i c h i s t h e nf e r m e n t e d b y t h e d r e n c h b a c t e r i a w i t h t h e p r o d u c t i o n o fl a c t i c a c i d , so m e a c e t i c a c i d a n d s m a l l a m o u n t s of f o r m i c a n db u t y r i c a c i d s . T h e b u t y r i c f e r m e n t a t i o n i s l ia b l e t o b e c o m et o o v i o l e n t . T h e s e a c i d s , a s t h e y a r e f o r m e d , n e u t r a l i z e t h el im e i n t h e

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