30 ANALYTICAL PROCESSES. 



are marked on the body of the rule, while that for the 

 specific gravity is placed on the sliding portion. 



The divisions are as follows : — 



Total solids . . . . i inch divided into tenths 



Fat I 164 inches " " " 



Specific Gravity . 0.254 " " " halves 



The rule is employed by adjusting the arrow point 

 to the graduation corresponding to the fat found, when 

 the figure for the total solids will coincide with that for 

 the observed specific gravity. This instrument does 

 not take into consideration the necessary correction for 

 poor skim milks, but the error from this cause will in 

 no case exceed .08 per cent of fat and may usually be 

 disregarded. 



TOTAIv PROTBIDS. 



This determination is best made by calculation from 

 the figure for total nitrogen obtained by Gunning's 

 modification of Kjeldahl's process. The reagents and 

 apparatus required are as follows ; — 



Standard Sulfuric Acid. — This should be about dec- 

 inormal, the exact value being determined by precipi- 

 tating a measured volume with barium chloride, collec- 

 ting and weighing the barium sulfate under the usual 

 precautions. 



Standard Barium Hydroxid. — This should be about 

 decinormal. The volumetric relation between this 

 solution and the standard sulfuric acid must be accur- 



