388 OTHER MILK PRODUCTS. 



the market consist of once precipitated casein, whicli has not 

 even been washed with water. 



To prepare a casein soluble in water, a small quantity of alkali 

 (sodium carbonate) is added to dissolve the protein, and the 

 solution is dried on hot rollers, as a fine spray, or in thin layers, 

 and the resulting solid ground. A casein nearly insoluble in 

 water, but easily soluble in dilute alkali solutions, may be pre- 

 pared by dissolving in ammonia, and evaporating the solution ; 

 practically all the ammonia passes ofT on drying. The curd 

 produced by rennet may also be used, but it is more difficult to 

 dissolve than that precipitated by acids. If the precipitated 

 casein is directly dried a hard, horny mass is produced, and as, 

 in the process of drying it is often overheated, it does not dissolve 

 easily in dilute alkali solutions. 



The following products of casein are commercial substances : — 



Plasmon, Tilia, etc. — The sodium compounds of casein, 

 containing the bulk of the salts of the milk. 



Sanatogen. — Casein combined with 5 per cent, of sodium 

 glycero-phosphate. 



Lacto-Somatose. — This consists of albumoses derived from 

 casein by heating with superheated steam. 



Sanose. — A mixture of 80 per cent, casein and 20 per cent, 

 albumoses. 



Nutrose. — The sodium compound of casein. 



Euoasin. — The ammonia compound of casein. 



Argonin. — The silver compound of casein. 



Lactoform consists essentially of casein precipitated by 

 metallic salts and subsequently hardened by formaldehyde. It 

 is employed in place of horn, ivory, ebony, amber, etc. By 

 painting walls twice with a 15 per cent, solution of casein and a 

 10 per cent, solution of zinc chloride, followed by an application 

 of strong formaldehyde solution, they may be rendered damp- 

 proof. 



Casein treated with formaldehyde is also used in the prepara- 

 tion of photographic plates, and for artificial tortoiseshell, etc. 



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. 



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

 as directed for dried milks (p. 149). 



Milk-sugar. — 25 grammes are dissolved in water, and if 



