108 Testing Milk and Its Products. 



SolSdB not fat=( I J^fg f -l)(100-f) 2.5 



The derivation of this formula is explained in the re- 

 port referred to. 



120. Short formulas. The tables made up from this 

 formula, giving the percentages of solids not fat corre- 

 sponding to certain per cents, of fat and lactometer 

 readings, are given in the Appendix. A careful exam- 

 ination of the tables will disclose the fact that the per 

 cent, of solids not fat increases uniformly at the rate 

 of .25, or one-fourth of a per cent, for each lactometer 

 degree, and .02 per cent, for each tenth of a per cent, of 

 fat. This relation is expressed by the following simple 

 formulas : 



Solids not f at=% L -f .2 f 

 Total solids=% L + 1.2 f, 



L being the lactometer reading at 60 F. (specific gravity 

 X 1000 1000), and f the per cent, or fat in the milk. 



Eule: a, To -find the per cent, of solids not fat in milk, add 

 two-tenths of the per cent, of fat to one- fourth of the lacto- 

 meter reading, and 



b, To find the per cent, of total solids in millc, add one and 

 two-tenths times the per cent, of fat to one-fourth of the lacto- 

 meter reading. 



These formulas and rules are easily remembered and 

 can be quickly applied without the use of tables. The 

 results obtained by using them do not differ more than 

 .04 per cent, from those of the complete formula for 

 milks containing up to 6 per cent, of fat, and may be 

 safely relied upon in practical work. 



The English dairy chemist Droop Richmond has 

 constructed an ingenious sliding "milk scale' 7 which en- 

 ables one to readily find the percentages of total solids 



