CASEIN PREPARATIONS. 



The following are typical analyses : 



TABLE XLL ANALYSES OF SUGARS. 



227 



Analysis of Casein Preparations. Moisture is estimated 

 by drying in the water-oven. 



Ash is determined by ignition at a temperature below red 

 heat ; a very pure casein should not be ignited in a platinum 

 basin, as the phosphorus of the casein attacks the platinum ; 

 in the presence of sufficient base a phosphate is formed. 



Total Proteins are deduced from the percentage of nitrogen 

 by multiplying by 6-39, or the casein may be estimated by 

 Sebelein's method. 



Fat is estimated by the Werner-Schmid, or Gottlieb methods, 

 as directed for dried milks (p. 219). 



Milk-sugar. Twenty-five grammes are dissolved in water, and, 

 if necessary, a little alkali, and made up to 500 c.c. ; the bulk of 

 the casein is precipitated by the addition of dilute hydrochloric 

 acid, the volume of this being noted. An aliquot portion of the 

 filtrate is neutralised, using phenol-phthalein as indicator, and 

 evaporated to less than 50 c.c. ; 1 c.c. of acid mercuric nitrate 

 is added, the volume made up to 50 c.c., and the solution filtered ; 

 to 40 c.c. of the filtrate, 2 c.c. of phospho-tungstic acid, and 2 c.c. 

 of sulphuric acid (1:1) are added, the solution filtered, and 

 the milk-sugar is estimated in the filtrate by polarisation. 



Soluble Matter. Five grammes are shaken with 100 c.c. of 

 distilled water for two hours ; of the clear filtrate 50 c.c. are 



N 

 titrated with alkali to estimate soluble acidity, and the aldehyde 



10 



N 



figure determined. By multiplying the c.c. of used by 40 the 



