Electrolytes on Copper Colloidal Solutions. 



585 



i. e. the copper particles move to the cathode in the solution ; 

 in other words, they are charged oppositely to those of the 

 silver and gold solutions worked with formerly. 



The major part of the paper will deal with, firstly, the 

 effect of solutions of two salts having the same acid radical 

 and, respectively, a monovalent and a trivalent metal, viz., 

 potassium sulphate and aluminium sulphate ; and, secondly, 

 with the effect of solutions of salts having the same metal 

 ion and, respectively, monovalent, divalent, and trivalent acid 

 radicals, viz.,<potassium chloride, potassium sulphate, potassium 

 phosphate, and potassium ferricyanide. The results of these 

 experiments fit in remarkably well with the theory first sug- 

 gested by the work of Picton and Linder * and of Hardy |, 

 and supported by the conclusions drawn from analogous 

 experiments on silver and gold solutions. 



3. Experimental Work. 



The solutions of copper were easily pre- 

 pared according to Bredig's method by 

 sparking with copper wires under the 

 surface of conductivity water, the specific 

 conductivity of which was usually about 

 2 x 10 " 6 . Using a current of from 5 to (5 

 amperes at a voltage of 110, 250 ccs. could 

 be produced in a short time. The resulting 

 solution was a very clear yellowish-brown 

 liquid in which the particles remained sus- 

 pended, apparently unchanged, for months. 

 Several samples were made, the average 

 copper content being *0088 grm. per 100 ccs. 



The velocity with which the particles 

 moved in an electric field was measured by 

 the U-tube method (see fig. 1) described in 

 a former paper J. Usually about 250 ccs. 

 of the solution sufficed to carry out one 

 series of experiments, and as each series was 

 completed a fresh stock of solution was 

 made from the same pieces of copper. In 

 every case the velocity of the particles in 

 the pure solution was found ; the results 

 of these observations are collected in 

 Table II. 



* Jour. Cheni. Soc s vol. lxi. p. 148 ; vol. Ixvii. p. 63 ; vol. Ixxi. p. 568. 



t Loc. cit. 



X Phil. Mag. eer. 6, vol. xi., April 1906. 



