16 



MILK-ANALTSIS. 



from 1.000 to 1.032 in passing into milk, tlie water receives 

 9.2 per cent, of milk solids. In other words, while the 

 density goes up only three per cent., the solids go up nine 

 per cent. It is, therefore, disadvantageous to estimate rise 

 in solid content by rise in density. Mineral substances, 

 when they dissolve in water, raise the density far more 

 rapidly than organic substances. The contrast in this re- 

 spect is very well shown when chloride of potassium is com- 

 pared with milk solids. Thus, a ten per cent, solution of 

 chloride of potassium has a specific gravity of 1.065 at 15° 

 Cent., whereas a ten per cent, solution of caseine and milk- 

 sugar has a specific gravity of about 1.035. 



To be of any value at all, a specific gravity determination 

 in the case of such a fluid as milk must be taken with ex- 

 treme accuracy ; and, as is well known, the taking of specific 

 gravities with great accuracy is not by any means one of the 

 most facile of operations, and is certainly not easier than the 

 taking of solid residues directly. 



From a careful consideration of the whole subject, I am 

 convinced that one of the most necessary steps to be taken 

 in mUk analysis is to abandon the use of the lactom- 

 eter. 



Tlie creamometer is a graduated tube, in which mUk is 

 allowed to stand and throw up cream, the volume of which 

 is afterwards to be read. 



It is, of course, unnecessary for the graduation to be 

 continued throughout the whole extent of the tube. If the 

 graduation be prolonged only for the uppermost fifteen per 

 cent., that will be amply sufficient for all practical pur- 

 poses — vide fig. 



Normal milk j'ields about ten per cent, of cream ; but 

 that is subject to great irregularity, and a milk may yield 

 very much loss without having been tampered with, or it 

 may yield the ten per cent., and, nevertheless, have been 



