72 DAIRY ANALYSIS 



- Wash out the alcoholic solution into a large basin, 

 and evaporate the alcohol on the water-bath ; add 

 enough hot water to make the bulk up to 150 to 200 c.c. 



N 

 and then add sufficient - hydrochloric acid solution to 



make with the volume already used in the titration 

 i c.c. more than the quantity equal to the 50 c.c. 

 alcoholic soda added ; heat on the water-bath till the 

 insoluble fatty acids float on the surface in a clear 

 layer, and filter through a wet filter ; wash out the 

 basin with hot water till the fatty acids are transferred 

 to the filter, and wash them well on the filter, stirring 

 them up with the jet of water ; at least a litre of water 

 is required for washing. With a good filter the fatty 

 acids do not run through ; when washed, allow all the 

 water to run out, and wash the filter with hot alcohol, 

 collecting the filtrate in a weighed flask, till all the 

 fatty acids are removed ; evaporate the alcohol, and dry 

 in the water-oven till the weight is constant ; this will 

 give the insoluble fatty acids. 



To estimate the soluble fatty acids, add a little 

 phenolphthalein solution to the filtrate from the 

 insoluble fatty acids, and titrate with alcoholic alkali 

 till a pink colour appears ; from the volume used cal- 

 culate the equivalent of -- acid, from this subtract the 



i c.c. added in excess of the soda added, multiply by 

 4.4, and divide by the weight of butter taken ; this will 

 give the soluble fatty acids in terms of butyric acid. 



Ave-Lallemant Method. Four grammes of fat are 

 saponified and neutralised as directed above, and the 

 alcohol evaporated ; 20 c.c. of water are added, and 

 the saponified fat evaporated to dryness. About 

 350 c.c. of hot water are added, and the soap solution 

 transferred to a 500 c.c, flask, which is placed on a 



N 

 water-bath. 100 c.c. - barium chloride solution are 



added with constant shaking, and the flask is left for 

 fifteen minutes on the water-bath ; it is then cooled? 



