CASEIN PEEPARATIONS. 389 



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 phenolphthalein as indicator, and 

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

 is added, the volunoe 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. 



Casein may be estimated by Sebelein's method (p. 130). The 

 following determinations may be made on the filtrate obtained by 

 adding acid mercuric nitrate (4 c.c. to 100 c.c.) to a 5 per cent. 

 solution ; calcium, magnesium, potash, soda, chlorides, sul- 

 phates, phosphates, citrates, acetates, and nitrogen in phospho- 

 tungstic acid precipitate. These determinations will give a 

 clue as to the mode of preparation of the casein. 



The difference between the phosphoric acid in the ash and 

 in the filtrate will give the organic phosphate. 



If sodium glycero-phosphate is present, the mineral phosphates 

 must be estimated in the filtrate obtained by adding acid mer- 

 curic nitrate, by precipitating with ammonium uiolybdate in tln^ 

 cold, and the sum of the mineral phosphates and those derived 

 from the gl}'cero-phosphates estimated in the asli of this filtrate ; 

 the difference between the P.,Or, multiplied by 3SU3 will give the 

 percentage of sodium ulycero-phosphate. 



The acidity and aldehyde figures are also useful determinations, 

 as is the solubility in dilute alkali (if not water soluble). 



Milk wine is produced by peptonising milk by means of 

 special ferments or organisms, precipitating with acid, and 

 fermenting, after the addition of sugar. 



Milk cocoa is a mixture of cocoa with dried milk solids. A 

 sample examined by the author had the following composition : — 



other 

 Water. Fut. .isli.. Prcjteiu. -<tarch. Milk-sugar. Sulistaiices. 



Percent. Percent. Percent. Percent. Percent. Percent. Percent. 

 .-,•93 25-91 .j02 19-50 5-70 11-70 2i'-24. 



Milk chocolate is a somewhat similar preparation, made by 

 incorporating dried milk with cane-sugar and cocoa. 



