300 THE CHEMISTRY OF DAIRYING 



fat can be easily and quickly determined; and the per- 

 centage of non-fatty solids, or total solids (N + F), can be 

 calculated from these data. From the above fundamental 

 equation the following are derived, by the usual algebraic 

 methods : 



G = '4N - o-8F 



Therefore 4N = G -f- o/8F T = N + F 



4 T = G + o-8F + 4 F 

 4 T = G + 4'8F 



T is the percentage of total solids. 



The formula T = o^G + i'2F is really that of Babcock, 

 though it is not always expressed in the same way. Richmond 

 holds that it is not strictly accurate, but requires the addition 

 of a constant, to which he assigns the value 0-14. Richmond's 

 formula, T = o'25G + i'2F -f 0*14, is the one commonly 

 used in this country. It corresponds very closely with the 

 analytical results obtained by the methods now in use. 

 It can be expressed in several different forms, and many 

 different modifications of it have been proposed. The 

 majority of them differ, ultimately, only in the value of 

 the constant. 



Specific Gravity of Milk Solids. The specific gravity of 

 the fat itself is 0-93, and that of the non-fatty solids r6 

 (water = i). In both cases the limits of variation are so small 

 as to be practically negligible. If the composition of the milk 

 is known, the specific gravity of the total solids can be cal- 

 culated according to the formula 



S is the specific gravity of the total solids (water = i), F and 

 N are the percentages of fat and non-fatty solids respectively 

 in the milk. 



According to Babcock, the specific gravity of the total 

 solids in genuine milk varies from about 1-25 to 1*34. It is 



