CHAPTER IX. 



USES OF CASEIN IN THE TEXTILE INDUSTRY, FOB FINISHING 

 COLOUR PRINTING, ETC. 



CASEIN is chiefly used in calico printing, more rarely in the 

 finishing department. The gummy ammoniacal solution of 

 casein is employed as a medium for printing and fixing 

 powdered pigments that will stand alkali. Fairly well-fixed 

 colours are obtained when the ammonia has been driven off 

 by vigorous drying or steaming. Solutions of casein in 

 lime-water can also be used in the same way ; in this case 

 the colours are fixed by the action of the air, the carbonic 

 acid in which acts upon the compound of lime and casein, 

 and forms calcium carbonate and insoluble casein. 



Pure casein is almost entirely insoluble in water, but. as 

 already mentioned, it will dissolve in water containing car- 

 bonates, phosphates, alkalies or even alkali chlorides, weak 

 alkali being the most efficient solvent. These solutions, in 

 which the casein is undoubtedly combined with the alkali 

 as a caseate, differ from solutions of albumen inasmuch as 

 they neither become turbid nor coagulate when heated. 

 They, however, acquire this property on the addition of 

 magnesium sulphate, and it also appears in solutions of 

 casein in lime-water, in which it is readily soluble. When 

 casein solutions are treated with acids, a flocculent curd is 

 precipitated, which may consist of a compound of the casein 

 with the added acid. A similar precipitate is produced 

 with acetic acid, but is redissolved on adding an excess of 



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