COAGULATION BY ALCOHOL 253 



ates of the alkalies and ammonium are clear, do not, except 

 lithium caseinate, show any increase in turbidity on warming, 

 and are not precipitated by the addition of finely divided in- 

 soluble substances or by passing through a clay filter; while 

 the aqueous solutions of the caseinates of the alkaline earths 

 are opalescent, show marked increase in turbidity on heating 

 their solutions to 35-45° C. which disappears on cooling, and are 

 precipitated from their solutions by the addition of finely divided 

 insoluble substances or by passage through a clay filter (4). 



The "neutral" or "basic" caseinates of the alkalies, upon 

 solution in water, depress its freezing point and the amount 

 of the depression is that of a solution of the same molecular 

 concentration as the alkaline solution which is employed as 

 solvent. The depression produced by calcium caseinate is much 

 less, being less than haK aS great (10). 



Equally concentrated solutions of the hydroxides of the alka- 

 lies and ammonium dissolve casein at approximately the same 

 rate. Solutions of the hydroxides of the alkaline earths dissolve 

 casein much more slowly (8). The rate of the solution of casein 

 by solutions of the hydroxides of the alkaHes is accelerated by 

 raising the temperature above 36 degrees; the rate of the solu- 

 tion of casein by solutions of calcium hydroxide is materially 

 diminished by a similar rise in temperature (6) . 



The caseinates of the alkaline earths are precipitated from their 

 solutions by the addition of small concentrations of the chloride 

 of the corresponding alkaline earth (7); the caseinates of the 

 alkalies are not precipitated by the addition of similar quan- 

 tities of the chlorides of the alkalies. 



I have alluded to the fact that the limiting concentration of 

 alcohol at which strontium caseinate is coagulated is consider- 

 ably higher than that at which calcium and barium caseinates 

 are coagulated. This is curious because we should expect, as 

 a rule, to find the salts of strontium possessed of properties in- 

 termediate between those of calcium and barium. It is therefore 

 the more interesting to observe that this is not the only respect 

 in which the caseinates of strontium exhibit behavior differing 

 from that of the caseinates of calcium and barium and approach- 

 ing the behavior of the caseinates of the alkalies; for casein 

 dissolves much more rapidly in solutions of strontium hydroxide 

 than in solutions of other alkaline earth hydroxides (8); the 



