ii BUTTER 169 



addition of a small quantity of this fat is very difficult to 

 detect, particularly as the Reichert-Meissl number of natural 

 butter has had to be lowered considerably in recent times. A 

 good indication of butter adulterated with cocoa-nut oil is the 

 relation between the iodine number and the Koettstorfer number, 

 for then the former is very low and the latter very high. The 

 iodine number of cocoa-nut fat lies between 8 and 9'5, and the 

 Koettstorfer number 253-271. Crismer's number for cocoa-nut 

 fat is 31. The special tests used for the detection of cocoa- 

 nut oil in butter are the following : 



1. Polenske s Neiu Butter Number. 



Polenske's method l is based upon the well-known fact that 

 the majority of the volatile acids in butter fat are soluble in 

 water, whilst those in cocoa-nut oil are insoluble. Further, as 

 has already been mentioned, the Reichert-Meissl number for 

 cocoa-nut fat is from 6-8, whilst the amount of JV/10 caustic 

 soda which is required to neutralise the insoluble fatty acids 

 which pass over in the same distillation is from 16-18 c.c. 



Polenske titrates the insoluble volatile fatty acids obtained 

 in the Reichert-Meissl method, and calls the number of cubic 

 centimetres of N/10 caustic soda which are used the " New 

 Butter Number." It would be more suitable to call this figure 

 the Polenske number, and this will be done whenever further 

 mention is made of the method. 



The Polenske number for pure butter fat stands in a certain 

 relation to the Reichert-Meissl number as long as the latter 

 does not exceed 27, but above that figure the same ratio is not 

 kept. For figures below 27, the Polenske number can be got 

 from the Reichert-Meissl number by means of the formula : 



R M "^ = Polenske number - 



IO 



For a Reichert-Meissl number above 27, the figure 7 must be 

 replaced by 5. 



Polenske has drawn up a table showing the relation between 

 the Reichert-Meissl and Polenske numbers in the case of pure 

 butter fat, which is as follows : 



1 Arbeiten aus dem Kaiserl. Gesundheitsamte, Vol. XX, p. 545 ; Ztifxchrift 

 fur Untermch. der Nahr.- und Genmsmittel, 1904, Vol. I, p. 273. 



