520 FIXED OILS, FATS AND WAXES 



in water and is removed during the first cleansing process which 

 consists in steeping the fleeces in water ; part is insoluble in water 

 and can subsequently be removed by benzene, acetone, or other 

 suitable solvent, forming, after evaporation, a brownish grease. It 

 is also removed when the fleeces are scoured with soap and water, 

 the second cleansing process. When the emulsion thus produced is 

 acidified the wool fat is separated together with the fat-acids produced 

 by the decomposition of the soap. These fat-acids can be converted 

 into the corresponding calcium salts and the wool fat separated by 

 treating the product with acetone ; the acetone solution, evaporated 

 to dryness, yields crude wool fat which has to be purified by suitable 

 means. 



Wool fat may also be extracted by scouring the fleeces with hot 

 water, and allowing the emulsion thus produced to stand, when 

 impure wool fat rises as a cream. This can be cleansed by repeatedly 

 mixing with water and separating by centrifugation, the resulting 

 wool fat being subjected to a final process of purification. 



Description. Purified wool fat is a yellowish, tenacious, unctuous 

 solid with a characteristic odour. It melts at about 42 and is soluble 

 in acetone, benzene, and the usual fat solvents. It may be 

 distinguished from other fats by its solubility in boiling alcohol and 

 also by the following test (for cholesteryl alcohol) : Dissolve 0-1 

 gramme in a mixture of 5 c.c. of chloroform and 0-5 c.c. of acetic 

 anhydride ; pour gently upon 5 c.c. of sulphuric acid ; a purplish 

 brown ring, passing into green is developed at the surface of contact. 



Constituents. Wool fat consists chiefly of cholesteryl and iso- 

 cholesteryl alcohols combined with lanoceric, lanopalmitic, carnaubic, 

 myristic, a little oleic, and possibly also palmitic and cerotic acids. 



5. Wool fat is largely used as an emollient and for promoting 

 the absorption of drugs by the skin. 



Adulterants. The most probable adulterants of wool fat are 

 mineral fats (soft paraffin) or animal and vegetable fats and oils. 

 Wool fat, like most waxes, is not readily attacked by boiling, aqueous 

 solution of potassium hydroxide, but may be saponified by boiling, 

 or heating under pressure, with an alcoholic solution of the same, 

 the saponification value varying from 90 to 102. Mineral fats are 

 not attacked by either aqueous or alcoholic solution of potassium 

 hydroxide, and their presence would lower the saponification value. 

 Animal and vegetable fats and oils would by the same treatment be 

 saponified and raise the saponification value ; they would also be 

 saponified by aqueous alkalies which would not attack wool fat or 

 mineral fats. Glycerin can be detected by shaking the wool fat with 

 hot water and evaporating the aqueous solution. 



