74 



ANALYSIS OF MILK. 



mineral matter ; this should agree within small limits with that 

 found. 



The Alteration of Specific Gravity by Change of 

 Temperature. — Milk, like all other substances, alters in specific 

 gravity by change of temperature. 



Though it contains a large amount of water, it does not share 

 the anomaly which this substance possesses of attaining its 

 maximum specific gravity at 4° C. (39° F.). It decreases in 

 specific gravity when heated from its freezing point — 0'55° C. 

 (31° F.). 



The following figures (Table VIII.) show the average apparent 

 expansion of milk in glass • — 



TABLE VIII.— Expansion of Milk. 



The expansion is greater with rich milk than with poor milk ; 

 the above figures referring to milk having a specific gravity of 

 1-032 and containing 3-8 per cent. fat. 



Table CXXXI. in the Appendix affords a means of correcting 

 to 60° F. the specific gravity of milk when taken by a lactometer 

 at any temperature from 33° F. to 85° F. The table gives specific 

 gravities from 1-020 (20 degrees) to 1-036 (36 degrees) and is 

 applicable to whole milk only. The portion from 45° F. to 75° F. 

 is, with a few alterations, due to Vieth ; this has been repeatedly 

 checked by the author, and in a few places slightly changed in 

 accordance with the results obtained. The other portion has 

 been calculated by the author. 



The table is used by looking up the degrees of specific 

 gravity found (or the nearest whole degree) in a horizontal 

 line, and the temperature in a vertical line ; the figure at the 

 intersection of the two lines is the specific gravity corrected to 

 60° F. 



The specific gravity of separated milk may be corrected to 

 60° F. by the following table. As the expansion is practically 

 uniform for the variations in quality met with, the table is given 

 in a simpler form. 



