DAIRY PRODUCTS. 65 



potash is measured by 50cc. pipette, which is allowed to drain into each 

 flask for exactly the same length of time. The flasks are closed with 

 glass marbles, placed upon the water bath and saponified at a tempera, 

 ture of about 50 C. After perfect solution has taken place they are 

 allowed to remain for an hour or two and then diluted with slightly 

 warmed distilled water. Into each flask and likewise into two beakers 

 containing 50cc. of the alcoholic potash are now run about Ice. of the 

 approximately semi-normal acid more than is necessary to neutralize 

 the 50cc. of alcoholic potash. The excess of the acid over the potash is 

 afterwards determined by the decinormal soda. The flasks after the 

 addition of the acid are nearly filled with water and gently agitated, then 

 placed on the water bath until the fatty acids form a clear stratum. 

 They are then allowed to cool and stand over night. On the following 

 morning the solutions from the cakes of fat are poured into a filter. 

 When the whole solution is on the filter the flasks are rinsed with 

 15 to 20cc. of cold distilled water, and when this is poured off about 150cc. 

 of hot water are added and the flasks briskly shaken for a minute or two. 

 Two good washings with hot water are believed to be enough. The 

 filtrates are now treated with the decinormal soda, the amount for the 

 excess of sulphuric acid deducted, the remainder being the index of the 

 soluble acids of the butter, which are calculated as butyric acid. 



The insoluble fatty acids in the flasks and the small amount that may 

 have passed on to the filter paper are allowed to remain until the fol- 

 lowing day, by which time the latter become air-dried and in a fit state 

 to rinse with ether. The fat in the flasks is then melted and poured, 

 together with the rinsings of the ether, into counterpoised dishes with 

 perpendicular sides, about 3 inches across and 1 J inches deep, and the 

 filter papers are also thoroughly washed with ether, the funnels being 

 covered during the process. After the evaporation of the ether a little 

 absolute alcohol is added, the dishes dried in the water-bath for half an 

 hour, cooled, and weighed. Afterwards they are again dried for twenty 

 minutes and re weighed. 



For a more convenient method of manipulating fatty acids, Blyth l 

 has recommended the following: 



The flask in which the sapouitication is made should be of 300 to 400cc. 

 capacity, with a rather long and narrow neck, furnished with an accu- 

 rately fitting stopper, through which two tubes pass, one provided with 

 a stop-cock to let out the liquid, and therefore terminating on a level 

 with the interior surface of the stopper, the other to let in the air, pro- 

 longed to nearly the bottom of the flask and externally bent siphon- 

 like. The fat is saponified in the flask and the soap decomposed in the 

 usual way ; when this is effected, the stopper is inserted, and the flask 

 is turned upside down and kept in that position during the entire wash- 

 ing process. Directly the whole of the fat has risen to the surface the 

 lower liquid is run off, whilst hot or cold water is introduced by opening 



1 Analyst, 1878, p. 112. 

 19330 No. 13 5 



