CALCULATION METHUD. 29 



sp. gr., fat and total solids are known, the third can 

 be calculated. Since the determination of the fat and 

 specific gravity can- be accurately made by rapid and 

 simple methods, the formulae become very servic- 

 able and should always be used to check the results. 

 That of Hehner and Richmond is now exclusively used, 

 having been based on extensive observation and perfect 

 processes of fat extraction. 



The formula is as follows: — 



F= .859 T -.2186 G 



in which F represents the fat, T the total solids and 

 G the specific gravity. This formula will suffice for 

 ordinary milks, but for poor skim milks it has been 

 found necessary to modify it as follows : — 



F== .859 T-. 2186 G-.05 (--2.S) 



This correction is to be applied only when G divi- 

 ded by T exceeds 2.5. 



In these formulae, G represents the last two units of 

 . the specific gravity and any decimal. Thus, if the 

 observed specific gravity be 1029.5, G will be 29.5. 



Tables calculated from these formulae will be found 

 in the appendix so that by reference to the proper col- 

 umns, the third datum may be obtained at once. 

 A still more ready means of applying the formula is by 

 the use of Richmond's slide rule. This has three 

 scales, two of which, for fat and total solids respectfully. 



