II 



BUTTER 165 



To make certain that no unsaponified fat remains, the residue 

 in the flask is again saponified with 10 c.c. of caustic potash of 

 the same strength as above, 20 c.c. of water being added, and 

 the liquid shaken out with 80-100 c.c. of ether just as before. 

 The ethereal solution is then washed with 5-10 c.c. of water, 

 filtered, and the ether distilled off. 



After the greater part of the ether has been got rid of in this 

 way, the remaining ethereal solution is poured into a small 

 glass crystallising dish, the ether completely evaporated off, 

 and the residue dissolved in the least possible quantity of 

 absolute alcohol, and allowed to crystallise out. The crystals 

 which first separate are then subjected to a crystallographic 

 examination. 1 The remaining alcohol is then completely 

 evaporated off on the water-bath, the dish placed on wire 

 gauze, and after covering with a watch-glass the contents 

 heated with 2-3 c.c. of acetic anhydride for about a quarter of 

 a minute. After removing the watch-glass the excess of acetic 

 anhydride can be got rid of on the water-bath. 



The residue in the dish is then warmed with sufficient 

 alcohol to dissolve the ester, and to avoid an immediate 

 crystallisation on cooling a little more alcohol is added and the 

 clear solution left to crystallise out. Until the temperature of 

 the solution has sunk to that of the room the dish must be 

 kept covered with a watch-glass. After half or two-thirds of 

 the liquid has evaporated, and the greater part of the ester 

 has crystallised out, the remainder is passed through a small 

 filter, and the solid that remains in the dish is transferred, with 

 the help of a spatula and a little 95 per cent, alcohol, to the 

 filter. The contents of the filter are returned to the crystallising 

 dish, dissolved in from 5 to 10 c.c. of absolute alcohol, according 

 to the quantity, and again allowed to crystallise. After the 

 greater part of the ester has crystallised out, it is filtered off 

 and subjected to further recrystallisation in the same manner 

 as long as sufficient material remains. After the third crystal- 

 lisation the melting point of the ester is determined, and again 

 after each subsequent recrystallisation, of which generally five 

 to seven are necessary. If, after recrystallising the ester in the 

 above way, the crystals last obtained do not melt completely at 



1 Zeitschrift fiir Untermchuny der Nahrunys- und Gennssmittel, 1898, Vol. I, 

 pp. 42 and 44 ; Ibid, Vol. I, pp. 48 and 546. 



