1 62 MILK AND DAIRY PRODUCTS PART 



begins to decline with regularity until the animal is almost dry. 

 During this latter period, abnormally low figures are often 

 obtained for the Reichert-Meissl number. 



A ration rich in oil has often been proved to cause a fall 

 in the Reichert-Meissl number, whereas one containing sugar 

 raises it. 1 When the cows begin to go out to grass the per- 

 centage of volatile fatty acids almost always falls, and remains 

 lower during that time than during winter feeding. There are 

 whole districts, for example, in Holland where the butter, 

 particularly during the autumn months, shows a very low 

 Reichert-Meissl number. 



From what has been stated above, it is easy to see that 

 to prove adulteration of butter with margarine may be very 

 difficult, even though the Reichert-Meissl number may be 

 unusually low. Where, however, the butter shows a Reichert- 

 Meissl number of less than 24, it must be regarded with 

 suspicion, and further tests must be made to prove its 

 genuineness. 



4. The Koettstorfer Number. 



Koettstorfer started from the fact that butter- fat, which 

 contains a larger proportion of fatty acids of low molecular 

 weight than other fats, must therefore contain more acid 

 groups than do the latter. He therefore adopted as measure 

 of this acid radicle the number of milligrams of caustic potash 

 which are required for the saponification of 1 g. of the fat 

 under analysis. The Koettstorfer number fluctuates between 

 220-5 and 232, whilst margarine fat shows only 192-200. 

 When a fat becomes rancid, the Koettstorfer number generally 

 rises. When employed in conjunction with one another the 

 Reichert-Meissl and the Koettstorfer numbers give very 

 important indications as to whether or not a butter has 

 been adulterated with margarine. 



5. The Phytosterine Acetate Test. 



On saponifying animal or vegetable fats there always remains 

 some non-saponifiable material which in the case of the animal 



1 Biedermann's Zentralblatt fur Agrikulturchemie, 1905, p. 406. 



