356 KEICHERT-WOLLNY NUMBER 



Aqueous soda saponifies butter very slowly and is now rarely or 

 never used. An alcoholic solution works much more rapidly and the 

 alcohol is readily expelled by heat before the soap is decomposed by 

 sulphuric acid. A solution of caustic soda in glycerol saponifies the 

 butter very quickly, especially as it can be raised to a high temperature, 

 and the presence of the glycerol does not interfere with subsequent 

 operations. This modification of the original Eeichert process, as it 

 is called, was introduced by Leffmann and Beam. The following re- 

 agents are used : 



Soda solution. 20 grammes of pure caustic so;! a are dissolved 

 in 20 c.c. of water ; 20 c.c. of the clear solution are then mixed with 

 180 c.c. of pure glycerol. 



Sulphuric acid. 1 volume of pure acid to 4 volumes of water. 



Barium hydrate. A decinormal solution. 



The sample is melted and filtered from casein, etc. ; 5 grammes 

 (about 5'75 c.c.) of the melted fat are then run into a 300 c c. flask, pre- 

 viously thoroughly dried and weighed. After cooling, the flask and 

 fat are weighed. Twenty c.c. of the glycerol solution of soda are then 

 run in and the flask heated directly over the lamp. After the water 

 (in the soda solution) has boiled off, the contents of the flask will be- 

 come quite clear in a few minutes. The flask, now containing glycerol 

 and soap, is allowed to cool and 135 c.c. of water added. When the 

 soap is dissolved, 5 c.c. of the sulphuric acid and a piece of pumice 

 are added, the flask is connected to a glass condenser fitted with a bulb 

 arrangement to prevent spirting, and 110 c.c. are distilled over in 

 half an hour. The distillate, which must be filtered if not clear, is 

 then titrated with the alkali after addition of a few drops of phenol- 

 phthalein. Five grammes of butter treated in this way require from 

 24 to 34 c.c. of decinormal alkali, while 5 grammes of most animal fats 

 require less than 1 c.c. 



Commercial "margarine," which consists of animal fats churned 

 with milk so as to acquire a flavour of butter, usually requires from 1 

 to 2 c.c. of decinormal alkali. 



Thus a specimen of "butter," 5 grammes of whose fat gave only 

 sufficient volatile acids to neutralise less than 24 c.c. of decinormal 

 alkali, was considered to be open to suspicion of containing some 

 foreign fat. 



It has, however, been shown that when the cows are far advanced 

 in lactation, and especially when fed upon poor pastures, their milk 

 fat may give numbers much lower than this for their volatile fatty 

 acids. 1 The writer's experience in South Africa also confirms this, 

 and the same applies to the " saponification equivalent" (really a 

 measure of the mean molecular weight of the fatty acids present). It 

 is therefore necessary to use caution in condemning any sample of 

 butter as being adulterated with margarine, from any data depending 

 upon measurements of the amounts of fatty acids of low molecular 

 weight present. 



Another method of distinguishing butter fat from other fats is by 



1 Van Eijn. The composition of Dutch butter, 1902, see also Brownlee, Jour. 

 Irish Dept. of Agric., April, 1910, and Crowther, Bulls. 62 and 66, Leeds Univ., 

 1904-1906. 





