CREAM. 



187 



This method is nob available for homogenised cream, and the 

 fat should be estimated by the Gottlieb or Werner-Schmid 

 methods. 



An indirect estimation of the percentage of fat may be made 

 from the total solids, and vice versd. For this purpose it is 

 assumed that the proportion of solids not fat to water in milk 

 is constant, an assumption which causes no appreciable error 

 in cream analysis. It is found that on the average 100 parts 

 of water contain 10-2 parts of solids not fat. 



The following formulae will express this relation : 



Let T = total solids, F = fat, and S = solids not fat. 



then F = 1-102 T - 10-2, S = 10 1 - O'l T, or 10 ~~ 



1-08 



The following table (XXX.) may be used :- 



TABLE XXX. RATIO OF FAT TO TOTAL SOLIDS IN CREAM. 



For the determination of milk-sugar by polarisation, the cream 

 should be diluted with water ; 50 grammes may be made up 

 to 100 c.c., and 1 c.c. of acid mercuric nitrate added. 



If total nitrogen is determined, the cream should be evapor- 

 ated in a wide-mouthed flask, and the bulk of the fat extracted, 

 as, otherwise, great charring of the fat takes place (if the cream 

 be treated by the Kjeldahl methf d), and much carbon, difficult to 

 dissolve, is produced. 



Density, The percentage of fat varies inversely as the density 

 of the cream. 



A formula connecting the two can be deduced from the formula 



