DIFFUSION. 31 



also the crystallization of albumins is apparently possible only in the 

 presence of certain mineral salts. Numerous attempts to bring this 

 about in the absence of salts have so far at least yielded only nega- 

 tive results. Of vegetable albumins, the phytovitellin of para-nuts, 

 the castor-oil bean, etc., yields well-defined crystals when the sub- 

 stance is dissolved in solutions of neutral salts at a temperature of 

 about 40 C., and is subsequently allowed to cool or evaporate. 

 Egg-albumin, the serum-albumin of the horse, and pure casein may 

 similarly be made to crystallize. The material thus obtained does 

 not represent pure albumins, however, but is apparently a compound 

 with the salts employed. The tendency to crystallization, moreover, 

 increases with repeated exposure to the various salt solutions in 

 which crystallization is to take place. 



The globulins have thus far not been obtained in crystalline form 

 by artificial means, but Paton has shown that after their passage 

 through the kidneys they may at times separate out in crystalline 

 form spontaneously. 



In the dry state the albumins usually occur in the form of a white 

 powder, or as yellowish, brittle, more or less opaque lamellae, which 

 are both odorless and tasteless. 



Solubility. Some of the albumins, such as serum-albumin and 

 egg-albumin, are soluble in water. Others are insoluble in water, 

 but dissolve in dilute saline solution, while still others are insoluble 

 in both water and dilute saline solution, but dissolve in dilute alka- 

 line or acid solutions. 



All albumins are soluble in concentrated acetic acid and in 

 strong solutions of the caustic alkalies, but in undergoing solution 

 they are more or less modified and transformed into syntonins or 

 alkaline albuminates. as the case may be (see below). In cold 

 absolute alcohol and ether albumins are insoluble, but in dilute 

 alcohol some of them dissolve with comparative ease. 



Behavior toward Neutral Salts and Alcohol. All albumins, 

 with the exception of certain deutero-albumoses and peptones, may 

 be precipitated from their neutral or feebly acid solutions by satura- 

 tion with ammonium sulphate. Other neutral salts of the alkalies 

 and alkaline earths, such as sodium chloride and magnesium sul- 

 phate, behave in a -different manner toward the individual representa- 

 tives of the group, and it is thus possible not only to separate the 

 albumins from a large number of other substances, but also from 

 each other. In being thus precipitated their structure and proper- 

 ties are not altered in the least. 



Strong alcohol acts in very much the same manner, but it is to be 

 noted that after prolonged exposure, and especially in the presence 

 of salts, the albumins pass over into the coagulated state, and then 

 remain refractory to all neutral solvents. 



Diffusion. Like the colloids of the inorganic world, so also are 

 the albumins practically incapable of diffusing through animal mem- 

 branes. This peculiarity Graham explained by the assumption that 



