110 CASEIN. 



and colours. Its preparation is based on the production of 

 a clear, non-milky casein, first proposed in the German 

 patent 115,681, granted, under date 15th July, 1899, to 

 Adolf Spitteler of Prien, Upper Bavaria. 



The specification of this patent states that the cheap, 

 imperfectly purified, commercial varieties of casein furnish 

 turbid solutions, which in turn yield products that are only 

 translucent, not transparent. True, according to Lundberg, 

 casein itself, when in the form of faintly alkaline solutions, 

 is soon transformed into alkali albuminate ; nevertheless, 

 these solutions will remain milky, both when heated and 

 when kept for days, if impure casein has been used ; neither 

 can they be clarified by repeated filtration. If such solutions 

 be precipitated, the substances causing the lack of transpar- 

 ency are thrown down as well, and the deposit when dried is 

 opaque in thick layers. 



It has, however, been observed that caustic alkalies pre- 

 cipitate these opaque substances and enable clear solutions 

 of casein to be obtained. 



Technical casein is mixed with 13 times its weight of 

 water, containing in solution 2 parts of Na 2 O per 100 of dry 

 casein. This gives a uniform milky liquid, which when 

 treated with progressively larger quantities of 5 per cent, 

 caustic soda furnishes the results expressed in the following 

 table. No further change is obtained by even doubling the 

 quantity of caustic soda, though the addition of larger quan- 

 tities of 20 per cent, soda lye cause precipitation of sodium 

 caseate, which redissolves on dilution with water. 



The action of caustic alkalies differs considerably with the 

 quantity employed. Several times the amount of alkali 

 necessary for solution may be added without any visible 

 change being produced, the solution rather becoming thinner. 

 On the other hand, if the addition of caustic lye be continued 

 further, the liquid begins to thicken, and finally separation 



