PHYTOSTERYL ACETATE TEST. 329 



does not yield correct results, owing to the formation of anhy- 

 drides on drying. 



From the difference between the potash absorption, and the 

 potash used for the insoluble fatty acids, an estimation of the 

 s(jluble fatty acids can be obtained. 



Bomer's Phytosteryl Acetate Method for Detection of 

 Vegetable Oils. — While butter-fat and other animal fats 

 contain cholesterol, vegetable oils are free from this alcohol, 

 and contain phytosteryl. There is a difference in crystalline 

 form and other properties between these alcohols, but the most 

 striking and reliable difference is thf melting point of the acetates. 



Fifty grammes of butter fat are saponified with 100 c.e. of 

 alcoholic caustic potash (200 grammes per litre), 200 c.c. of 

 water are added, and the solution shaken out three times with 

 ether, 500 c.c. being used for the first extraction, and "250 c.c. 

 for the others. A larger amount of butter fat may be taken, 

 and shaken out three times with an equal volume of warm alcohol, 

 the alcohol evaporated, and the residue saponified with 2n ( ., . 

 <il' causti(/ potash, the solution diluted with 50 c.c. of watn, 

 and shaken out tliicc times with 100 c.c. of ether; sufficient 

 of the unsaponifiable alcohol i.s thus extracted for the test, and 

 the manipulation is easier. 



The ether is evaporated, and the residue agiii)i saponified with 

 a little alcoholic potash .solution, diluted with twice the volume 

 of water, and shaken out with three or four successive quantities 

 of ether. The ethereal solution is wa.shed three times with 5 e.c. 

 of water, filtered, and the ether evaporated. 



Tlie residue is transferred to a small basin (this may he accom- 

 plished by not quite distilling off the ether, and pouring tlie 

 •ethereal solution left into the basin), the solvent completely 

 evaporated, and the residue treated with 2 or 3 c.c. of acetic 

 anhydride, and cu\'ered with a watch-glass. The acetic anhy- 

 dride is boiled for about a quarter of a minute, and the excess 

 evaporated on the water-bath. 



The acetate is dissolved in sufficient alcohol to prevent im- 

 mediate ci ystallisation on cooling, and the solution left to crystal- 

 lise : when about two-thirds of the alcohol has evaporated, the 

 crystals are separated by filtration, washed with a very little 

 ;t5 per cent, alcohol, redissol\"ed in hot alcohol, and recrystaUised ; 

 the recrystallisation is repeated five to seven times, and the 

 melting point of the crystals determined after the third and 

 subsequent recrystallisations. 



Cholesteryl acetate melts at 115'4 C. (corrected), and phyto- 

 steryl acetate at 127 , if on continued recrystallisation the melting 

 point rises above 117° the presence of phytosteryl acetate is 

 Certain. 



