vin ' THE SALTING-OUT OF ALBUMINS 283 



be added in equivalent amounts to two portions of a 1 : 1000 HC1- 

 solution of the reserve material from the seeds, of Picea excelsa, the 

 sodium salt will cause a precipitate long before the potash salt does 

 so, because the mobilities of the sodium ion are much less than that 

 of the potassium ions, namely, as 44 '4: 65 '2. Similarly equivalent 

 solutions of the chlorides of magnesium, strontium, and barium stand 

 in the proportions of 0'311 : 0*366 : 0'414, while the mobilities of 

 these elements are as 49 : 54 : 57'3. Posternak was, however, not the 

 first to point out the importance of the mobilibity of ions ; this was 

 first done by Spring * who compared solutions having the same con- 

 ductivity (chlorides of K, Na, Rb. Li, Ca, NH 3 ) and found that they 

 produced flocculation in the order of the mobility of their ions, except 

 in the case of lithium chloride, which takes much less time to coagulate 

 than does the potash salt, because lithium chloride undergoes hydro- 

 lysis and thereby gives rise to the formation of hydrogen ions, which 

 possess the greatest mobility. 



In addition to the changes which micellae undergo under the 

 influence of ions and of non-dissociated salt molecules, they are said 

 to possess * adhesiveness,' a term based on Duclaux's ' molecular 

 adhesion,' which is the same as what others call ' surface attraction ' 

 or ' adsorption.' As the adhesive energy is proportional to the 

 extent of the surface, and as different albumins differ from one another 

 in the degree of their adhesive affinity, it follows that albumins of 

 different origin must possess micellae of different sizes. As an 

 increase of temperature augments the micellar 'adhesiveness' the 

 micellae must possess the power of increasing their surface with a 

 rise of temperature. This increase in size is termed micellar dilata- 

 bility or elasticity. 



Posternak does not believe in the Virchow-Hofmeister explanation 

 of the action of neutral salts in coagulating albumins by the with- 

 drawal t of water, as the reserve material of Picea excelsa seeds dissolved 

 in 1 : 1000 HC1 is readily precipitated by traces of salt, while it is 

 not rendered even cloudy on being saturated with glucose (see also 

 Spring, p. 298). He believes the micellae of albumins to be provided 

 with Ehrlich's haptophore-groups, by means of which they attract the 

 non-dissociated salt molecules, which then form a protective envelope, 

 and so protect the micellae from being dissolved by the ions, as 

 explained above. 



The weaker a solution is in proteid the greater must be the 

 amount of salt we require to add to produce flocculation : 



1 W. Spring, Bull, des science, Acad. Roy. de Belg. 1900, p. 483. 



