SPECIFIC GRAVITY, 



77 



the specific gravity minus 1,000, so (degrees of specific volume) 



is 1,000 minus 1,000 times the specific volume. 



In Table XIII. the values of degrees of specific volume for 

 each half degree of specific gravity from 20 to 36 are given. 



TABLE XIII. SPECIFIC GRAVITY AND VOLUME OF MILK. 



It is seen from the formula? later, that 1 per cent, by weight 

 lowers the specific volume to the same extent as 1 gramme per 

 100 c.c. raises the specific gravity i.e., specific volume, not 

 specific gravity, varies directly as percentage by weight. 



Mode of Averaging Specific Gravities. It is not, there- 

 fore, correct in averaging milk analyses, where specific gravities 

 and percentages by weight are expressed, to obtain the average 

 specific gravity by adding the specific gravities together and 

 dividing by the total number, but specific gravities must be first 

 calculated to specific volumes, and these averaged, and the 

 average specific gravity deduced from the average specific volume. 



Thus, to average the following analyses : 

 Specific gravity, . 1-022 Total solids, . . 20-0 



. 1-036 :-*.: . 10-0 



The average total solids is - - = 15 ; but the average 



2j 



1*022 -I 1*036 1 



specific gravity is not- - = 1 -029, but 



- = 1-0289. 



0-9719 



