TO UTILIZE SCRAPS OF PLATINUM
2
262 SCHOOL SCIENCE AND MATHEMATICS TO UTILIZE SCRAPS OF PLATINUM. NICHOLAS KNIGHT, Cornell College, Mount Vernon, Iowa. An interesting and valuable "inorganic preparation,^ and one which will use to good advantage the pieces of platinum foil and wire which accumulate more or less rapidly in all chemical lab- oratories is to change such scraps of platinum into pure hydro- platinic chloride, Ha Pt Ck In order to prepare this compound it is necessary to remove the two or three per cent of iridium which .is nearly always in alloy with platinum. Five or six grams of the platinum are carefully cleaned in the palm of the hand with moist sea sand and these dissolved in a por- celain evaporating dish on the water bath, with aqua regia. Suc- cessive portions of aqua regia must be added until all the metal is dissolved. The solution is evaporated nearly to dryness. A little distilled water is added, and the evaporation continued. It may be necessary to add ten or twelve successive portions of water until all odor of nitrogen peroxide is absent. Water is added to the residue which is filtered; the filtrate is heated to boiling. Caustic soda is added to strong alkalinity, then a few drops of ethyl alcohol. It is next acidulated with hydro- chloric acid and a solution of potassium chloride is added. After standing some hours, it is filtered. The precipitate is washed with a dilute solution of potassium chloride. After thoroughly drying the precipitate, it is removed to an evaporating dish, and crushed to a fine powder. It is removed to a combustion tube of about 40 cm. in length. This is placed in a combustion furnace, and heated for half an hour with small flames, while a stream of dry hydrogen passes through to reduce to metallic platinum. When cool, the substance is transferred to an evaporating dish, and crushed to a fine powder. It is washed several hundred times (1,000-1,200 times may be necessary), with hot water by decan- tation, until a few drops of the washings give no precipitate or cloudiness with silver nitrate. This metallic platinum is dried and weighed on the rough balance in order afterwards to make a five or ten per cent solution of the hydro-platinic chloride. It is transferred to an evaporating dish, dissolved in aqua regia, and evaporated, while distilled water is added from time to time, until
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Transcript of TO UTILIZE SCRAPS OF PLATINUM
262 SCHOOL SCIENCE AND MATHEMATICS
TO UTILIZE SCRAPS OF PLATINUM.
NICHOLAS KNIGHT,Cornell College, Mount Vernon, Iowa.
An interesting and valuable "inorganic preparation,^ and onewhich will use to good advantage the pieces of platinum foil andwire which accumulate more or less rapidly in all chemical lab-oratories is to change such scraps of platinum into pure hydro-platinic chloride, Ha Pt Ck In order to prepare this compoundit is necessary to remove the two or three per cent of iridiumwhich .is nearly always in alloy with platinum.
Five or six grams of the platinum are carefully cleaned in thepalm of the hand with moist sea sand and these dissolved in a por-celain evaporating dish on the water bath, with aqua regia. Suc-cessive portions of aqua regia must be added until all the metalis dissolved. The solution is evaporated nearly to dryness. Alittle distilled water is added, and the evaporation continued. Itmay be necessary to add ten or twelve successive portions of wateruntil all odor of nitrogen peroxide is absent.Water is added to the residue which is filtered; the filtrate is
heated to boiling. Caustic soda is added to strong alkalinity, thena few drops of ethyl alcohol. It is next acidulated with hydro-chloric acid and a solution of potassium chloride is added. Afterstanding some hours, it is filtered. The precipitate is washedwith a dilute solution of potassium chloride.
After thoroughly drying the precipitate, it is removed to an
evaporating dish, and crushed to a fine powder. It is removedto a combustion tube of about 40 cm. in length. This is placed in
a combustion furnace, and heated for half an hour with smallflames, while a stream of dry hydrogen passes through to reduceto metallic platinum.When cool, the substance is transferred to an evaporating dish,
and crushed to a fine powder. It is washed several hundred times
(1,000-1,200 times may be necessary), with hot water by decan-tation, until a few drops of the washings give no precipitate or
cloudiness with silver nitrate. This metallic platinum is driedand weighed on the rough balance in order afterwards to make a
five or ten per cent solution of the hydro-platinic chloride. It istransferred to an evaporating dish, dissolved in aqua regia, andevaporated, while distilled water is added from time to time, until
EXPANSION AND COMPRESSION 263
no further odor of nitrogen peroxide is discernible. The residueis dissolved in water up to the required strength.The experiment is not above the reach of the ordinary high
school student, and is one which will keep the restless, energeticboy busy during his laboratory periods, for at least two or threeweeks. The following are the equations that express the princi-pal reactions involved:4HC1+4HN03=4C1+4H20+4N02Ir+4Cl==IrCL2lrCL+8NaOH==2lr(OH)34-7NaCl+NaC10+H20.The few drops of alcohol decompose the sodium hypochlorite
with the formation of acetaldehyde.NaC10+GHeO=NaCl+CH3, CHO+KOIr(OH)3+3HCl=IrCl3+3lLO.The iridious chloride is not precipitated by potassium chloride
while the hydro platinic chloride is precipitated.H.PlCL+2KCl=K2PtClo+2HClK2Cl2,PtCL+4H==Pt+2.KCl+4HClPt+2HCl+4Cl=H2PtCk
COOLING BY EXPANSION AND WARMING BY COMPRESSION.CHARLES EMERSON PEET,
Lewis Institute.The following method of showing cooling by expansion, and
condensation of the water vapor of the air into a visible cloud ofwater particles, may be of interest to instructors of physiography.It is a method I have used with success for several years. Theapparatus necessary is: i. An air pump. 2. A bell jar. 3. Abottle with snug fitting cork, coated with vaseline. The bottle iscorked and placed under the bell jar and the air is exhausted fromthe bell jar. The cork is pushed out of the bottle by the air in-side. The sudden expansion causes cooling enough to condensethe water vapor into a cloud which remains visible for a consid-erable time. Slow leakage of the air into the bell jar may producewarming by enough to re-evaporate the water. This ^warmingby compression is made more striking if the bell jar is providedwith a stop-cock by which the air may be admitted more rapidlyand in a manner which is apparent to the class. The success of theexperiment varies with the humidity of the air, but under the mostunfavorable circumstances, it is never an entire failure. The sizeof bottle to be used and the force with which the cork should bepressed into it can easily be determined by trial. The cloud inthe bottle may be made more clearly visible from the distance, ofcourse, by providing it with a proper background.
