114 Testing Milk and Its Products. 



ids of low specific gravities. The specific gravity of the milk 

 solids is calculated by means of Fleischmann 's formula 



t 



s=- 



100 s -100 

 t — 



S being the sp. gr. of the milk solids, s that of the milk and t 

 the total solids of the milk. 



Example: A sample of milk has been found to contain 13.0 

 per cent, of solids, sp. gr. 1.032; then ^°°^| |' ^~'"° =3.101; 

 13.0-3.101=9.899; -g^l^tj'^ =1.31, the specific gravity of the milk 

 solids. 



The specific gravity of the solids does not change if the milk 

 is watered, while it is increased when the milk is skimmed. If a 

 sample of milk of the composition given in the preceding ex- 

 ample had been watered so as to reduce the solids to 11.7 per 

 cent, and the specific gravity to 1.0291 (as would be the case 

 when 10 per cent, of water was added), we would again have, 

 by calculation as above, S^l.31. If, on the other hand, the 

 milk was skimmed so as to reduce the solids to 11.7 per cent., 

 thereby increasing the specific gravity of the milk to, say 1.035, 

 we woidd have by substituting these values in the preceding 

 formula, S=1.41, showing conclusively that the milk had been 

 skimmed. 



An addition of skim milk to whole milk would have the same 

 effect as skimming, as regards the composition of the latter, and 

 the specific gravity of its solids. 



The specific gravity of pure butter fat at 60° F. is .93, and 

 of the fat-free milk solids, 1.5847 (Fleischmann). The solids of 

 skim milk have a specific gravity of 1.56. Samples of whole 

 milk, the solids of which have a specific gravity above 1.34 are 

 suspicious, and a specific gravity over 1.40 is conclusive evidence 

 of skimming. 



To facilitate the calculation of the specific gravity of milk 

 solids. Table IV is given in the Appendix, showing at a glance 



the value of ^^^^ for specific gravities between 1.019 and 



1.0369. An example will readily illustrate the use of the table. 



Example: A sample of milk has a specific gravity of 1.0343 



and contains 12.25 per cent, solids. In Table IV, we find in the 



