Smith.] 46 [Nov. I. 1878. 



Contributions from the Laboratory of the University of Pennsylvania, Wo. 

 XVI. — On the Electrolytic Estimation of Cadmium. 



By Edgab P. Smith, Ph. D. 



i /'rm! ,it the meeting of the American Philosophical Society, Nov. 1, 1878.) 



In a recent article published in the American Journal of Science and Arts 

 (Vol. XVI., Sept., 1878), Prof. F. W. Clarke calls attention to the estima 

 lion of cadmium by electrolysis, which, however, proved unsuccess 

 ful — the cadmium being indeed thrown out of the solution but in such 

 a form as to enclose impurities; yielding consequently unsatisfactory 

 results. 



Out of curiosity, to see what mightbe effected by substituting some other 

 salt for the chloride, I employed an acetate solution and met with success, 

 as the following experiments will show : 



I. .1450 grms. cadmium oxide were dissolved in acetic acid, the excess 

 of the latter expelled upon a water bath and the platinum crucible then 

 about half rilled with water, and placed upon a copper ring connected with 

 the negative pole of a two-cell Bunsen battery, while joined to the wire 

 leading from the positive pole was a strip of platinum foil extending into 

 the acetate solution. The deposition of the cadmium upon the sides of the 

 platinum crucible was regular and in a perfectly crystalline grayish white 

 layer. In about three hours the separation was complete. The cadmium 

 was first washed with distilled water, then with alcohol and finally with 

 ether. It was dried over sulphuric acid. The metallic cadmium weighed 

 .1270 grms. corresponding to 87.58 '/c Cd. The calculated percentage of 

 metal in the oxide is 87.50. 



II. .2046 grms. cadmium oxide placed in a small broad platinum crucible 

 were dissolved in acetic acid and after evaporating the excess of the latter 

 water was added — the solution, however, remaining rather concentrated. 

 The platinum vessel was connected with the negative pole of a bichromate 

 battery. To the copper wire of the positive pole was attached a pla- 

 tinum wire from which was suspended a small platinum crucible, which 

 dipped into the solution in the larger vessel. The space between the walls 

 of the two crucibles was not more than the eighth of an inch. Only two 

 cells of the battery were employed. The deposit of cadmium here as in 

 the first experiment was perfectly crystalline and metallic in appearance. 

 Not the slightest trace of spongy metal was visible. The separation of the 

 metal was finished in about the same time as in (I), and it was then washed 

 and dried as above. Found .1790 grms. metal — corresponding to 87.48 



% Cd. 



Prom the various experiments made I have discovered that to obtain 

 good results the following should be observed : 1st. Work with rather 

 concentrated solutions of the acetate. 2d. Employ a sufficient number of 

 cells of either battery to produce a rapid and rather energetic current. 



i ictober 31, 187?. 



