INDIAN J. CHEM., VOL. 16A, SEPTEMBER 1978

K-l. For this system both the Xu and Q12 para-meters are negative. This indicates the solute-solvent specific interaction leading to ordering inthe solution. There are ample evidence of formationof hydrogen-bonded solute-solvent complex for thissystem.

Using the Berthelot's geometrical mean rule Xuwas calculated from rei a tion (8)Xl2 = PI*[l-(SlP2*/SZPl*)!]2 ... (8)From Xu observed (experimentally) and X12 calcu-lated (theoretically) the ratio ~ = YJ12(obS.)/1J12(calc.)is obtained. The value for this system is 1·125.The ra tio ~, grea ter than unity, also shows thepresence of solute-solvent complex.

TABLE 5 - COMPARISONOF VALUESOF GE, HE, SE ANDV E OF EQUlMOLARMIX1'UREOF CHLOROFORM+ THF

Temp. GEJ mole'?

HEJ mole"!

SE VEJ mole-1K-1 ems mole'?

20 -108830 -1034 -269215 -5,42 -0,35040 -984

Theoretical when Xu = 157'8 J cm-8 and Qu = 030 -1930 -2702 - -1,28

Theoretical when X12 = 157'8 J cm-3 and Q12 = 0·179230 -1030 -2702 -1·28

TABLE 6 - PARAMETERSOF PURE LIQUIDS AT 30°USED IN FLORY'S THEORyI6-18

Chloroform Tetrahydrofuran

V (ern" mole'"](t x 103 (1(-1)[jXI06 (atrrr+)v* (em" mole=)T* (K)r, (J cm-S)v

84·191·286

105·562'09

4636·0610·2

1·3075

82·241'213

96'563'57

4768·0646·3

1·2938

The results have been compared with Flory'stheory16,17. Following Flory's notions, excess func-tions HE, GE and VE can theoretically be calculatedfrom Eqs. (4)-(6).

2 f'OJ""" ,...,

HE = ~l x.Nvt'(vt1_V-1) +x1v!62x12V- •.. (4)•

+XIV~a2;-lX12 (5)

VE = (XIV~+X2V~)(V-<P:Vl -<P2V·2) (6)The va lues of the properties of pure componentsv, IX, ~ along with the corresponding values ofcharacteristic volumes (v*), temperatures (1*) pres-sures (P*) and of reduced volume (v) are listed inTable 6. X12 is an adjustable interaction para-meter. It is a usual practice to obtain X12 fromHE data and then calculate other excess functions.Here also we have obtained X12 from experimentalHE data-", The predicted excess functions GE andVE are much lower than the experimentally observed.

The departure of GE from the experimental datais attributed to the fact tha t X 12 is energetic inorigin. In order to get the agreement of calculatedand experimental GE, it is necessary to considerthe entropy contributions. Therefore, modifiedequation (7) of Flory's theory is used-"

GE ~ ~:'N'" [("'~;)+3T' In(~t::~)]-1

+X1Vl*6z(X12V-Q12 T) ... (7)In Eq. (7), Q12 is a parameter for entropy contri-

bution due to contact interactions. It is obtainedfrom the best fit to GE data using the value of Xuobtained from experimental HE data. The valuesof X12 and Q12 are -157·8 J ern'? and -0·1792 J cm-s

800

References1. DESHPANDE, D. D. & OSWAL, S. L., j. ch em . Soc.,

Faraday Trans. 1,68 (1972), 1059.2. DESHPANDE, D. D. & OSWAL, S. L., j. chem . Thermo-

dynamics, 7 (1975), 155.3. WEISSBERGER, A., Techniques of organic chemistry,

Vol. VII (Interscience, New York), 1959.4. SANNIGRAHI,A. B. & CHANDRA,A. K., L. Phys, Chem.,

67 (1963), 1105.5. TIMMERMANS, J., Physico-chemical constants of pure

Organic compounds (Elsevier, Amsterdam), 1959.6. SWIETOSLAWSKI, \V., Azeotropy and polyazeotropy

(Pergamon, London), 1963, 32.7. DESHPANDE, D. D. & PANDYA, M. V., Trans, Faraday

Soc., 63 (1967), 2149.8. LIPKIN, M. R., DAVISON, J. T., HARVEY, W. T. &

KURTZ, S. S.,Ind. Engng Chem . (Anal.), 16 (1944), 55.9. DESHPANDE,D. D., BHATGADDE,L. G., OSWAL, S. L. &

PRABHU, C. S., J. Chem. Engng Data, 16 (1971), 469,10. REDLICH, O. & KISTER, A. 1., Ind. Engng Chem., 40

(1948), 345.11. BARKER, J. A., Aust. J. Chem., 6 (1953), 207.12. MCGLASHAN,M. L., PURE, J. E. & SAINSBURY,E. J.,

Trans. Faraday Soc., 50 (1954), 1284.13. ROWLINSON,J. S., LAMBERT, J. D., ROBERTS, J. s. &

WIKINSON, V. T., Proc. Roy. Soc. (A), 196 (1949),113.

14. KUDCHADKAR,A. P., ALANI, G. & ZWOLINSKI, B. J.,Chem, Rev., 68 (1968), 659.

15. DINCER, S. & VAN NESS, H. C., j. chem, Engng Data,16 (1971), 378.

16. FLORY, P. J., J. Am. chem, Soc., 87 (1965), 1833.17. ABE, A. & FLORY, P. J., J. Am. chem, Soc., 87 (1965),

1838.18. ORWOLL,R. A. & FLORY, P. J., j. Am. chem . Soc., 89

(1967), 6822.

Flow Through Porous Medium: Part 11-Permeability of Water & Solutions of Ammo-nium Nitrate, Sulphate & Phosphate Through

Treated Pine wooa Membrane

R. L. BLOKHRA,M. L. PARMAR& R. K. SHARMADepartment of Chemistry, Himachal Pradesh University

Summer Hill, Simla 171005

Received 22 October 1977; accepted 15 February 1978

Permeability coefficients of water and solutions ofNH.N03, (NH')2S0. and (NH.),PO., at differentconcentrations, and at 25° and 30° through a treatedpine wood membrane are reported. It has beenobserved that the permeability is minimum for waterand maximum for (NH.).SO. as compared to othersalt solutions. The results have been discussed interms of the pulping of the wood.

THE litera ture on the transport phenomena suchas permeation, osmosis, etc., in both natural

and artificial membranes is enormous and studiesof these involve a number of disciplines in scienceand technology. A piece of wood of small thickness(2-5 mm) may be classified under compositemembranes'. Only a few studies on permea bilityof water and some non-electrolyte solutions- (ureasolutions) from a viewpoint of knowing the structureof composite membrane, preservation of wood andpulping operations are available3,4.

The passage of liquids through openings thatare one micron or more in diameter follows the samelaws that explain flaw in pipes, capillaries, etc."and a technique for measuring flow of water hasbeen described by Choong and Kimbler", Thistype of flow may be much less than ordinaryviscous flow and controls the longitudinal and la teralpermeability. It has been further observed thatthe resistance to fungal attack is usually greaterfor the less permeable woods. In these the growthof fungi is apparently inhibited by reduction in theamount of oxygen available for metabolic activity.The longitudinal permeability" makes possible thethe onset preservative treatment. Some workers?observed that treatment with salt solutions affectsthe longitudinal flow of liquids through the pinewood.

In the present investigation the longitudinalpermea bility coefficient of water and of solutionsof ammonium salts viz. nitrate, sulphate andphosphate, through four-year-old pine wood hasbeen described with a view to investigating indetail the effects of ammonium saIts on the per-mea bility of water through pine wood membrane.

A piece of four-yea r-old pine wood of 4 mmthickness was procured from the forest in HimachalPradesh (India) at a height of 8000 ft above meansea-level. The freshly cut wood piece was washedwith water and then treated with benzene andmethanol to remove some of the unwanted organicmatters (resins). The wood piece was treated withformalin (5%) overnight to destroy fungus growth,if any, and this wood membrane was then fixed inan all glass apparatus described elsewhere''.

The motion of the liquid, in the horizontalcapillary, at various time intervals was noted atdifferent values of pressure difference. The distancein the capillary could be read up to ±0·05 em andtime up to ±0'05 sec. The pressure difference wasnoted with the help of cathetometer reading upto 0·001 em. The whole apparatus was kept inan air thermostat maintained to an accuracy of± 0·02° with the help of an electronic relay andtoluene regula tor.

The values of the volume flow at various pressuredifferences across the wood membrane are givenin Table 1.

The plot J versus AP (see Fig. 1) is linear, sug-gesting that [« llI> or J = LllAP, where Lll is thephenomenological coefficient describing the flowthrough wood membrane. This linear relationfurther suggests that 'Poisseuille's law' of flow,through capillaries or tubes holds good in thiscomposite membrane as well.

NOTES

TABLE 1- FLOW OF DIFFERENT LIQUIDSTHROUGH PINE WOOD MEMBRANE AT

VARIOUS PRESSURE DIFFERENCES

!;"P* ]* X 10' !;"P* ]* X 10'(cm'/sec) (cm'/see)

WATER AT 25° WATER AT 30°

20 0·34 20 0·3530 0·51 30 0·4840 0'69 40 0·7350 0·89 50 0·9260 1·09 60 1-14

O'OlM NH.NO. AT O'OlM NH.NO. AT25° 30°

10 0·20 10 0'2115 0'27 15 0·3020 0·36 20 0·04425 0·47 25 0'5630 0'56 30 0'66

0'02M NH,NO. AT 0'04M NH.NO. AT30° 30°

10 0·26 10 0'2815 0'43 15 0'4420 0'58 20 0·6125 0'74 25 0·7530 0·89 30 0·90

0'06M NH.N03 AT O'lM NH.N03 AT30° 30°

10 0'29 10 0·3115 0'46 15 0'5020 0·60 20 0·7225 0·76 25 0·8930 0'89 30 1·07

O'OlM (NH.).SO. AT O'OlM (NH')3PO. AT30° 30°

10 0'31 10 0'2715 0'43 15 0·4320 0'63 20 0'5625 0'80 25 0'6930 0'95 30 0·84

*!;"P (height of the liquid level in em) is the pressuredifference across the wood membrane, and J is the volumeflow of the liquid.

Similarly mass flow can also be written as":.. q

JM = Lp a AP where JM represents the mass flowing

per second through the membrane, Lp is the ordinarypermeability, q is the area of cross-section of themembrane, a is the thickness of the membrane andllP is the pressure difference across the membrane.Further, the mass of the liquid flowing through

dxthe membrane can also be written as JM = dt p7t r;.Here x is the distance travelled in time t by theliquid in the capillary, P is the density of the liquidand rc is the radius of the capillary. Thereforedx 2 7tr~dt p7trc=Lp-y.AP •.. (1)

where rm is the radius of the membrane through

801

1.2

1.0

.... 0.8~

'"<,....E 0·6v

•.....

0·1.

0.2

INDIAN J. CHEM., VOL. 16A, SEPTEMBER 1978

-o----s---o- 0.01 to! (NH4)3 POI.

~ 001 !vi NH, N03

~H20

10 5020 30 40

t:. P(cm OF LleUIO)

Fig. 1 - Plots of ] versus t1P for the chemically treatedwood membrane at 30°

which the liquid is flowing. Since AP = h Pg, Eq.(1) can be written as

dx 2 7tr;,dt P1'Wc=LpThpg ••• (2)

where h is the height of the pressure head from thecapillary and g is the acceleration due to gravity.On rearranging (2) the ordinary permeability perg will be given by Eq. (3)

dx r; i\Lp=dt'r;.hg ... (3)

Considering that the molecular weight of waterdoes not change with the addition of the salt forthe concentration range reported here, Lp per molewill become

t.,= ~ [dX . r~2. i.] ...(4)18 dt 'I'm hg

The values of Lp obtained from (4) for differentliquids (Table 2) show that the permeability of waterchanges negligibly with a temperature differenceof 5°.

On comparing J = LllAP with Poisseuille's law,Lll can be written a S10:

Lll = 7tL.rt /8YJi\ •.. (5)where ri is the average capillary radii of the woodmembrane and in terms of Lp, we get

Lp i= 7tL.rt/8YJi\

orLp = 7tL.rt/8YJi\ ... (6)

802

TABLE 2 - VALUES OF Lp FOR DIFFERENT LISjUIDS ATDIFFERENT TEMPERATURES

"!1 Temp. Liquid Lp x 1011(0C) (mole dyrr ! ern sec<)

25 Water 3·8330 Water 3'8925 0·01 M NH,NOa 3·9430 O'OIM NH.NOa 4'5230 O'OlM (NH.)aPO. 5·8230 O'OlM (NH,)aSO. 6·47

TABLE 3 - VALUES OF Lp AT DIFFERENTCONCENTRATIONS OF AMMONIUM NITRATE AT 30°

[NH.NOJ Lp x lO" [NH.NOa] Lpxl011

M (mole dyn"! cm M (mole dyn+ emsec-l) sec=)

0·01 4·52 0'06 6'280·02 6'00 0·10 7·210'04 6·21

60Expression (6), therefore, suggests that the per-meability is inversely proportional to the viscosityof the solution. Earlier investigations'! showedthat in the case of ammonium nitrate solutions, theviscosity decreases with increase in concentration.This indicates that the permeability should increasewith the increase in the concentration and it hasbeen found to be so as is evident from the data inTable 3. Further from Table 2 it is evident thatthe permeability of the different fluids increasesin the order: ~NH4)2S04 > (NH4hP04 > NH4NOain water indicating that the solution of ammoniumsulphate will ease the process of pulping better thanthe other salt solutior s reported here since pulpingof wood is easier if the permeability of the liquidin which the pulp is being made is greater'.

One of the authors (M.L.P.) is highly thankfulto the CSIR, New Delhi, for the award of a post-doctoral fellowship.

References

1. LAKSHMINARAYANAIAH, N., Transport phenomena inmembrane (Academic Press, New York), 1969.

2. KANFERT, F. H. & BEHR, E. A., Ind. Engng Chern,(Ind. Edn) , 34 (1942), 1510.

3. PANSHIN, A. J. & ZEEUW, C. D., Textbook of woodtechnology (McGraw-Hill, New York), 1970, 217.

4. HILLIS, W. E. (ed.), Wood extractives and their signi-ficance to the pulp and paper industry (Academic Press,New York), 1962.

5. CHOONG, E. T., FOGG, P. J. & KIMBLER, O. K., WoodSci., 4 (1) (1971), 32.

6. SMITH, D. N. & LEE, E., Forest product research: SPecialReport 13 (Department of Scientific & IndustrialResearch, London), 1958.

7. LINDGREN, R. M., Proc. Am. Wood Preserver's Assoc.,48 (1952), 158.

8. BLOKHRA, R. L. & PARMAR, M. L., Aust. J. Chem.,(communicated), (1977).

9. HAASE, R. & STEINERT, C., Z. phys. Chem, (N.F.), 21(1959), 270.

10. BLOKHRA, R. L. & PARMAR, M. L., J. electroanal, Chem.,62 (1975), 373.

11. CONWAY, B. E. & BARRADAS, R. G., Chemical physics ofionic solutions (John Wiley, New York), 1964, 63.