196 The Analysis of Dairy Produce [326 



The working out of this formula is as follows : 

 The difference between the percentage of these acids in 

 butter fat and in animal fat is 95*5 — 87*5 = 8. 



It is, therefore, on this 8 per cent, that we must base our 

 calculation. 



If an excess of 8 % (over 87*5 %) means 100 % foreign fat,- 

 then „ „ 1% „ „ *°?% 



N<>/ IooN o/ 



55 55 « /O S> 55 A , /O 55 



Supposing that we have found a per cent, insoluble fatty 

 acids; then 



N m (a - 8 7 '5), 



.*. the percentage of foreign fat present = — -  - , 



o 

 which equals 12*5 (a — 87-5). 



326. Reichert Meisl Method.— It was stated in para- 

 graph 321 that butter fat differed from most other natural fats, 

 in that it contained a certain quantity of volatile fatty acids. 

 This quantity is usually stated as the number of c.c. of 

 decinormal alkali (barium hydrate) required to neutralise the 

 volatile acids in 5 grams of fat. The fat is first saponified by 

 heating with a solution of soda in glycerin, then the acids are 

 set free by dilute sulphuric acid, and the volatile portion is 

 distilled off. The acidity of the distillate is estimated by 

 means of standard barium hydrate. The solutions required 

 are : 



Caustic Soda Solution. Fifty grams of caustic soda is 

 dissolved in a small quantity of water and the solution 

 diluted to 100 c.c. It is then mixed with 500 grams of pure 

 glycerin. 



Dilute Sulphuric Acid. The ordinary dilute sulphuric acid 

 must be diluted until 5 c.c. just neutralises 2 c.c. of the glycerin- 

 caustic-soda solution. 



