460 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Caseinogen. 



Not only is caseinogen the chief protein present in milk, forming 

 as it does about 80 per cent, but also it is of great value as a food- 

 stuff: in milk, in the form of cheese, in numerous commercial prepara- 

 tions, such as plasmon, sanatogen, nutrose and many others. It is used 

 commercially for many purposes, e.g. in making painting materials, in 

 making adhesives, in making artificial ivory, celluloid, bone, buttons ; 

 in waterproofing paper materials ; in making fireproof materials when 

 mixed with asbestos ; in glazing, in solidifying oils, in making soaps. 



The food-stuffs are generally fine powders soluble in water ; they 

 are frequently mixed with carbohydrates and medicinal substances^ 

 such as sodium glycerophosphate in sanatogen. The caseinogen is 

 usually in the form of a sodium, potassium, or ammonium salt pre- 

 pared by treatment with sodium bicarbonate, sodium citrate, sodium 

 phosphate. The amount of protein in these substances is from 20 to 

 95 per cent 



Preparation. 



Commercial caseinogen is prepared by treating skimmed milk with 

 dilute sulphuric or hydrochloric acid. The precipitate of caseinogen 

 is filtered off and dried ; the dry preparation contains about IO per cent, 

 of water. 



Pure caseinogen is prepared by acidifying skimmed milk which has 

 been diluted with water, washing the precipitate with water, dissolving 

 it in dilute alkali, reprecipitating and repeating this procedure several 

 times. The precipitate is finally treated with alcohol and ether, to re- 

 move fat, and dried. 



A very pure caseinogen is prepared as follows : 



1000 c.c. of skim milk are diluted with 6000 c.c. of water and the 

 caseinogen is precipitated by adding, with constant stirring, about 1000 c.c. of 

 dilute acetic acid (10-15 c - c - glacial acetic acid in 1000 c.c.), avoiding a 

 marked excess of acid. 



The precipitate is allowed to settle and the solution decanted ; it is washed 

 with large amounts of distilled water until the washings are no longer acid. 

 The precipitate is dissolved in dilute ammonia (5 c.c. of '880 ammonia in 1000 

 c.c. of water) to form a solution neutral to litmus. The solution is diluted with 

 6000 c.c. of water and precipitated with dilute acetic acid. Less acid is now 

 required than before. The precipitate is washed as before, redissolved in am- 

 monia and again thrown down by acid. The process is repeated five or six 

 times. The precipitate is finally filtered off on a Buchner funnel and washed 

 free from acid. The washed precipitate is suspended in 1000 c.c. of *iN 

 hydrochloric acid and shaken for 2 hours to remove inorganic salts. This is 

 repeated twice. It is washed free from acid, treated with 1000 c.c. each of 

 strong alcohol and ether and dried at room temperature. It is finely ground 

 and dried at 45-50- The ash content of this preparation is from -25 to -3 

 per cent. 



For conductivity experiments the caseinogen is shaken several times with 

 conductivity water before it is dried with pure alcohol and ether. 



