56 COLLOID CHEMISTRY OF THE PROTEINS 



are present. Our exposition of the combination of albumin 

 with acids, and of the physico-chemical properties of the pro- 

 ducts formed thereby, will be based mostly on recent researches, 

 which, without disturbing the equilibrium between protein and 

 acid, have led, on the basis of direct determination of hydrion 

 concentrations, to a pretty comprehensive view of the pheno- 

 mena which occur. 



Measurements of electrical conductivity, as undertaken by 

 J. Sjoqvist* in the first instance, give a limited insight into the 

 behaviour of proteins with acids. As long as combination 

 occurs, the conductivity shows a considerable decrease owing 

 to the disappearance of the rapidly-moving hydrogen ions. 

 This, however, is an indirect and uncertain way of arriving at 

 the capacity of the albumin for combination with acid, because, 

 as we shall see, the mobility of the charged albumin particles 

 is in no wise independent of the quantity of acid combined 

 therewith, and, moreover, on account of the high mobility of the 

 hydrogen ion, a slight excess of uncombined acid makes a 

 considerable difference to the conductivity of the mixture. 



The important work of F. A. Hofmann and O. Cohnheim,f 

 in which the acceleration of the inversion of cane sugar by 

 hydrogen ions was applied to estimate the hydrion content of 

 mixtures of proteins and acids, only fails on account of the 

 slight sensitiveness of the method in such cases. 



The work of St. Bugarsky and L. Liebermann J marks a stage 

 of notable progress in the investigation of the matter under 

 discussion. These authors introduced the measurement of 

 H and Cl ions by the electrometric method to determine the 

 combination of acids, bases, and common salt with proteins. 

 Until recently, this work was one of the main supports of the 

 view of the salt-like nature of the acid and alkali albumins 

 which was commonly accepted. The products were therefore 

 considered to be subject in typical fashion to the laws of 

 electrolytic dissociation and of hydrolysis, which were conse- 

 quently applied to them. 



* Skand. Arch. PhysioL, 1894, 5, 277 ; 1895, 6, 255. 

 t O. Cohnheim, Zeitsch. Bid., 1896, 33, 489 ; see also W. B. Hardy, 

 /. PhysioL , 1905, 33, 251. 



I Arch. ges. PhysioL, 1898, 72, 51. 



