Metallic Salts hy an Electric Current. 213 



a copper positive electrode immersed, there is dissolved in 

 the positive cell an equivalent of copper for that deposited 

 upon the negative pole, but there is formed besides a great 

 quantity of white powder resembling a subchloride of copper, 

 slightly soluble in water, which adheres to the pole with great 

 tenacity, sometimes, if the current be continued several hours, 

 to the depth of y'^jth of an inch, by which means the positive 

 pole will lose, according to the strength of acid and the power 

 of battery, from 1^ to 3 times the quantity of that deposited 

 upon the negative electrode. 



The substance formed and collected upon the pole I have 

 not yet had an opportunity of analysing, but its general pro- 

 perties differ from those of the chloride or subchloride of cop- 

 per; it is white when newly formed, but becomes green by 

 washing and exposure to the air, and then slightly deliques- 

 cent. It gives an immediate deep blue colour with ammonia, 

 dissolves in nitric acid with effervescence, also in hydrochloric 

 acid, and is not precipitated by dilution, but is converted into 

 the chloride: 9,5 grains gave 6*3 grs. of chlorine and ll'Sgrs. 

 of copper ; it is probably an oxychloride. 



By way of comparing these results with the practical ex- 

 perience alluded to, I instituted a series of small experiments, 

 in which the second question referred to was particularly no- 

 ticed ; a few of these I will state in detail. 



400 grains of cyanide of potassium were dissolved in 12 

 ounces of distilled water, divided into equal parts and placed 

 in the two divisions of a decomposing apparatus, being sepa- 

 rated by a porous diaphragm; silver electrodes of equal size 

 were put into each and connected with a battery of 9 pairs of 

 zinc and copper plates; the negative division was so constructed 

 that the gas evolved from the electrode was received into a gra- 

 duated jar; the current was continued until 25 cubic inches of 

 gas were obtained ; the two electrodes were then weighed ; the 

 negative was found unchanged, the positive had lost 62 grains, 

 which is 8 grains more than the equivalent of hydrogen 

 evolved. 



The same experiment was repeated with 600 grains of cya- 

 nide of potassium to the 12 ounces of water; the positive elec- 

 trode in this instance had lost 70*5 grs., being 16*5 grs. more 

 than the equivalent of gas evolved. 



Again repeated, having 800 grs. of cyanide of potassium, 

 when the positive electrode had lost 85 grs., or 31 grs. more 

 than the equivalent of gas evolved. The waste or destruction 

 of zinc in the battery for these three experiments, amounted 

 to 506 grs., which is more than an equivalent of zinc for the 



