1891.] 106 [Warwick. 



The Electrolysis of Metallic Formates. 



By Bill Sloane Warwick. 



(Read before the American Philosophical Society, November 6, 1S91.) 



The facility with which many metallic formates could he reduced to the 

 metallic state by heat, or in the case of silver and mercury, even by the 

 action of light, having led to the hope that they might be employed with 

 particular advantage in electrolysis, the following series of experiments 

 were made upon solutions of copper, zinc and cadmium formates, in order 

 to ascertain the effect of dilution, temperature and pole separation, as well 

 as the conditions necessary in order to effect their quantitative estimation and 

 separation. The current was generated by a battery of ten cells, of the 

 "crowfoot " type, each cell being 3.1 dm. in height, by 1.9 dm. in diame- 

 ter, and having a capacity of 2 liters ; the dimensions of the zincs were 

 1.5 cm. by 1.5 cm., and of the radiating copper plates constituting the 

 positive pole 1.5 cm. by 1.5 cm. By means of this battery a compara- 

 tively uniform current of 2.8 c.c. electrolytic gas per minute was gener- 

 ated after the cells had been in use for some time. 



The strength of the current was measured by means of an ordinary 

 voltameter, and was ascertained before and after the completion of the 

 experiment. For the deposition of small quantities of metal, thick platinum- 

 foil electrodes were used, 3.8 cm. wide, and immersed to the depth of 3.8 

 cm. in the solution. For quantities above .05 gram, they were unsatis- 

 factory, the metal showing a great tendency to separate in a spongy con- 

 dition at the edge. In the earlier determinations a platinum dish was 

 used, weighing about 67 grams, and having a capacity of 150 c.c. ; in the 

 later ones a dish weighing 117 grams, and with a capacity of 275 c.c, was 

 employed. The results obtained with the larger dish were necessarily 

 somewhat less exact than with the one of smaller size. The positive pole 

 consisted of a thick platinum wire, the lower portion of which was wound 

 into a horizontal spiral. In some of the separations it was found expedi- 

 ent to substitute for the spiral a small platinum crucible 2.5 cm. in height 

 and 2.8 cm. in diameter, closed by a cork, through which passed a copper 

 wire in contact with the bottom of the crucible. In order to regulate the 

 distance between the poles, a filter stand was used, having inserted on its 

 movable arm. an ordinary binding screw, to which the positive pole was 

 attached. 



The following formates were prepared : 



Copper Formate. 



This salt was made by precipitating cupric oxide from a hot solution of 

 copper sulphate, by means of caustic potash ; the precipitate was washed 

 by decantation until free from traces of potash ; it was then dissolved in 

 formic acid having the sp. gr. 1.015, obtained in the usual way from oxalic 



