194 The Analysis of Dairy Produce [324 



25 c.c. alcoholic KHO after saponification required 



4-2 N HC1 ; 

 2 



N 

 1 c.c. — HC1 neutralises '028 gram KHO ; 



.*. Amount of alkali used = (22*1 — 4-2) x '028 



= 17*9 x 28 = 501*2 milligrams. 



501*2 

 This divided by weight of fat = ; =228*1. 



The Koettstorfer number for pure butter fat varies from 

 221*5 to 2 33> averaging 227*25. The number given by oleo- 

 margarine is about 195*5. I n tne example just quoted, the 

 material was pure butter fat. Had the number fallen below 222 

 or 223, it would have been viewed with suspicion, whilst 

 had it fallen below 221*5 ^ would certainly have been adulte- 

 rated. 



An approximate idea of the percentage of foreign fat may 

 be obtained from the formula : 



(227*25 — n) x 3*17, 



where n is the Koettstorfer number found by experiment. 



Should the number indicate that the butter has been adul- 

 terated, it is advisable to use one of the more definte methods 

 described below. 



324. Hehner's Process. — Weigh out about 4 grams of the 

 butter fat so obtained in a tared 8-oz. conical flask ; add 10 c.c. 

 of saturated alcoholic potash. Heat gently on the water bath, 

 shaking from time to time, until the whole of the fat has turned 

 into a soap. The end of the reaction is easily seen from the 

 fact that the unsaponified fat floats as a yellow oily drop on 

 the surface of the liquid. This drop gradually diminishes, 

 and finally disappears. When the saponification is complete, 

 dilute with 50 c.c of water and allow the alcohol entirely to 



