ON THE ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 181 



results showed the presence of 0*2 to 0-3 iiigr. of iron in the electrolysed 

 solution. Nevertheless, as in the experiments of Series II., the error in 

 the weight of iron deposited is on the plus side. 



4. The Presence of Carbon in Iron deposited from Ammonium Oxalate Solution, 

 and the Determination of its Amount. By Charles A. Kohn, M.Sc, Ph.D., 

 and F. J. Beislee. 



To ascertain the presence of carbon in the metal deposited under the 

 above conditions the following method was adopted :— A solution of ferric 

 chloride, neutralised with ammonium hydrate, and to which ammonium 

 oxalate was added, was electrolysed under the usual conditions, a piece of 

 platinum foil being employed as the cathode. After the electrolysis the 

 foil was thoroughly washed, then dried, and rolled up for combustion. 

 The combustion was carried out in an ordinary combustion tube in a 

 current of oxygen, a solution of barium hydrate being used for the 

 absorption of the carbon dioxide. In every case a blank experiment was 

 conducted for one hour before the introduction of the deposited iron, and 

 the absorption bulbs weighed both at the beginning and end of the blank 

 experiment ; no difficulty, however, was found in keeping out all traces 

 of carbon dioxide. The results tabulated below leave no doubt as to the 

 presence of carbon in the deposited metal ; the quantity appears to be 

 independent of the quantity of iron precipitated, but increases with the 

 quantity of ammonium oxalate in the solution electrolysed, when this is 

 completely decomposed. The results are likely to err on the low side, as 

 the combustion of the carbon deposited with the iron is likely to be 

 incomplete. In order to make sure that the carbon dioxide was not 

 derived from any slight residues that might have adhered to the iron from 

 the alcohol used in the washing of the deposit, this washing was omitted 

 in experiments 3 and 4, and the precipitated metal dried in vacuo after 

 washing with water. Further, in experiment 4 the deposited iron, which 

 was beautifully crystalline, was detached as far as possible from the 

 platinum, and this portion (a) very completely washed with water before 

 drying, so as to be certain that the carbon did not arise from any adhering 

 traces of the decomposed oxalate solution ; the iron that still remained on 

 the platinum was combusted separately (b). 



Series V. 



The variations in current density and electromotive force do not seem 

 to make any appreciable difference. On an average the iron deposited 

 from a solution containing 6 gr. of ammonium oxalate contains 0-84 mgr. 

 of carbon, and, therefore, proportionately the results recorded in Series 11. 



