278 CHEMISTRY OF THE PROTEIDS CHAP. 



as are obtained on coagulating egg-white, there is set up but little 

 interference with the strength of the current. 



In the liquid chain represented above by A to E, we have salt 

 solutions at the end, while in the middle are equivalent solutions of 

 alkalies and acids in equal volumes, and of such strength as to form 

 by their union a salt solution of the same concentration as seen in 

 the end-links A and E. Given such a chain, no current is set up, 

 though a chemical union takes place. 



If two solutions of an acid varying in their concentration are inter- 

 polated between the same salt solution, a current passes from the 

 stronger to the feebler solution, the electro-motive force increasing 

 with the difference in concentration. If the dilute acid is replaced by 

 water, the current passes from the acid to the water, and with the 

 dilution of the acid diminishes in electro-motive force. Here again 

 the current is caused by the hydrogen-ions migrating rapidly from a 

 place of greater to that of lesser osmotic pressure, although the hydrogen 

 -ion is not subjected to a greater pressure than is its fellow ion. 



The greatest difference of potential will be set up in solutions to 

 which is added an electrolyte the radicals of which differ greatly in 

 their rate of migration, as is the case with hydrochloric acid, for 

 example, H = 320 and Cl' = 65, while no differences of potential can 

 be obtained, for example, from potassium chloride [K = 65 and 

 Cr=65]. The facts just stated will allow us to understand, if 

 colloids owe their existence to carrying definite charges, how such 

 charges will be influenced by electrolytes ; how in some places the 

 colloidal charge will be diminished while in others it will be in- 

 creased, or what comes to the same, how in the former case bigger 

 aggregates are formed, while in the latter instance the original 

 aggregates will become smaller or even pass into solution. Thus by 

 the diffusion of electrolytes alone the original state of the colloid 

 becomes greatly altered, and if in addition new insoluble compounds 

 are formed between the radicals of the electrolyte and the colloid, then 

 the temporary structural changes brought about by the disturbance of 

 the electrical equilibrium may become ' fixed.' 



The author has explained on p. 259 that, according to his view, a 

 colloid remains a colloid only as long as it carries a definite electro- 

 positive or electro-negative load, and that a non-electric condition is 

 induced by ions of the opposite electrical charge (Picton and Linder, 

 Spring) a view which is also supported by Hardy's experiment on heat- 

 coagulated albumin. The latter in an alkaline solution behaves as an 

 anion, while in an acid medium it behaves like a kation. The author 

 assumed that H-ions or OH'-ions combined with the colloid to form 



