INFLUENCE OF ELECTRICAL CONDITION 



113 



valent, divalent and trivalent metals are in the ratios 1: 30: 1650. 

 Prost, employing the hydrosol of cadmium sulphide, obtained a 

 similar relation, while Linder and Picton found that the precipi- 

 tating powers of different salts of a given metal are proportional 

 to their equivalent conductivities and that the relative precipi- 

 tating powers of the sulphates of univalent, divalent, and trivalent 

 metals can be expressed by the ratios 1 : 35 : 1023. 



In all of these cases the colloid employed was electronegative, 

 that is, on electrolysis it migrated to the anode. The experi- 

 ments which we have cited show that in such cases the ion of 

 the added electrolyte which is effective in bringing about precipi- 

 tation is the cation. In 1899, however, Hardy (21) showed that 

 egg-albumin, modified by heating its solution so as to partially 

 coagulate the protein, may be induced to travel either to the 

 anode or to the cathode by simply changing the reaction of its 

 solutions. In acid solutions the protein behaves like a cation, 

 migrating to the cathode; in alkaline solutions it behaves like 

 an anion, migrating to the anode. In alkaline solutions, the 

 cations of added salts proved to be the active agents in precipi- 

 tating egg-albumin, while in acid solutions the precipitating 

 power of the cation proved to be altogether subordinate to that 

 of the anion (22). The following illustrate his results: 



PROTEIN IN PRESENCE OF TRACE OF ALKALI, ELECTRO- 

 NEGATIVE 

 Temperature 16 degrees. Coagulating salt 1 gram-mol. in 80,000 cc. 



PROTEIN IN PRESENCE OF TRACE OF ACID, ELECTRO- 

 POSITIVE 



