248 



THE ANALYSIS OF BUTTER FAT. 



Blank experiments should be performed ; the figure for the 

 soluble blank may be sometimes high (2 c.c.), without affecting 

 the accuracy of the results. 



The soluble acids obtained by the Polenske process are prac- 

 tically the same as those given by the Reichert-Wollny method. 



The average figure for the soluble fatty acids is 28-4 c.c., but 

 considerable variation is observed ; in very rare cases figures 

 slightly exceeding 40 have been obtained, while exceptional 

 low figures of 14 have been observed as lower limits. These 

 very high or very low figures are rare ; low figures have usually 

 been observed in cases where the butter is produced from the 

 milk of cows near the end of lactation, especially if the animals 

 have been exposed to inclement weather. 



The average of the results of different observers shows that 

 out of 100 samples 



3 will probably yield Reichert-Wollny figures over 30 c.c. 

 86 between 26 and 30 c.c. 



7 25 and 26 c.c. 



below 25 c.c. 



All samples giving below 25 c.c. may be looked upon as sus- 

 picious, and should be investigated further. 



The Polenske figure varies with the Reichert-Wollny figure, and 

 the following table shows the relation which is also expressed 

 by the formula R-W X 0-033 - 0-6155 = Iog 10 (P - 0-48) ; 

 this relation is approximately correct for butters and for mixtures 

 with all fats other than coconut and palm-kernel oils. The 

 maximum allowable Polenske figure may be calculated by sub- 

 stituting 1-0 for 0-48 in the formula : 



TABLE XLVI. 



