16 THE GENERAL CHARACTERS OF THE PROTEINS 



into combination with the edestin and no longer remains a free ion 

 in solution. Acetates of zinc and mercury have no solvent action. 



The solubility of serum-globulin in salt solutions has been in- 

 vestigated by J. Mellanby. He found that the amount of globulin 

 dissolved by a neutral salt depends upon the percentage of protein 

 present and not upon the total quantity of salt. If a suspension of 

 globulin be treated with a salt solution of given percentage, the 

 amount of the protein dissolved will depend upon the strength of 

 the suspension ; more protein, for example, will be dissolved from a 

 5 per cent, suspension treated with a given quantity of salt solution 

 than would be dissolved if the same quantity of a 2 per cent, sus- 

 pension be treated in the same way. With regard to the solution 

 capacity of various salts, he found that neutral salts with monovalent 

 ions have the same efficiency ; those composed of a monovalent 

 positive ion and a divalent negative ion, or of a divalent positive 

 and monovalent negative ion have also the same efficiency as one 

 another. The salts of this latter class have a greater efficiency than 

 those of the former. Mellanby concludes that the solution of glob- 

 ulins by neutral salts depends upon the forces exerted by the ions ; 

 that monovalent ions, whether negative or positive, are equally effective 

 in producing solutions ; that divalent ions, whether negative or posi- 

 tive, are also equally effective, but more effective than monovalent 

 ions. 



Another view as to the solution of globulins by salts is that a 

 molecular compound of the type GBS (G = globulin, B = base, 

 S = acid) is formed, which is readily hydrolysed by water, with the 

 liberation of insoluble globulin : 



GBS + H 2 O = GHOH + BS. 



Such molecular compounds would be stable, therefore, only in pre- 

 sence of a large excess of the salt (Hardy). 



In the present state of knowledge but little can be said with 

 certainty as to the nature of the solution of those proteins in salt 

 solutions, which are insoluble in pure water. 



SECTION III. SOLUBILITY OF PROTEINS IN ORGANIC SOLVENTS. 



Some peptones and proteoses, as has been already mentioned, 

 are soluble in alcohol. Certain proteins of plant origin are insoluble 

 in water and absolute alcohol, but soluble in dilute alcohol. Bodies 

 of this class have been subjected to an exhaustive examination 

 chiefly by Ritthausen, and by Osborne and his co-workers. A 

 typical protein of this class is the gliadin obtained from wheat. 

 These bodies are generally soluble in some other organic solvents ; 

 zein, for example, the alcohol-soluble protein from maize, will dissolve 

 in glacial acetic acid, in crystallised phenol on warming and in 

 glycerol. In water and absolute alcohol it is perfectly insoluble ; it 

 is most soluble in alcohol of 85-95 per cent., and is but little soluble 

 in alcohol of less than 50 per cent. 



Mayer and Terroine have recently made a curious observation 

 with reference to the alcohol solubility of proteins. They have shown 

 that certain proteins which have been precipitated from a dialysed 

 aqueous solution by alcohol acquire the property of redissolving in 



