ox THE ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 179 



2. The Influence of Ammonium Chloride on the Electrohjtic 

 Detennination of Iron. 



Since any iron solution in the ordinary course of analysis is likely to be 

 acid with hydrochloric acid, a few experiments were made to decide whether 

 the ammonium chloride formed by neutralising it has any deterrent effect 

 on the deposition of the metal, since Classen states that it is desirable to 

 remove free hydrochloric acid by evaporation previous to the electrolysis. 

 1 gr. of ammonium chloride was added to each of the solutions electrolysed 

 under the conditions tabulated below ; from the results it is evident that 

 the addition is without influence on the determination of the iron. 



Series III. 



3. The complete Separation of the Iron ivhen deposited from Ammonium Oxalate 

 Solution : the Sulphocyanide Reaction for Iron under the conditions of the 

 Experiments. By Charles A. Kohx, M.Sc, Ph.D., F. J. Bkislee, and H. H. 

 Froysell. 



The apparent accuracy of the results obtained in the electrolytic 

 deposition of iron from ammonium oxalate solution has led the method to 

 be regarded as free from the source of error generally associated with the 

 deposition of metals from solutions of organic salts, viz. the separation of 

 carbon with the metal at the cathode. Citrate and tartrate solutions both 

 yield deposits containing a considerable proportion of carbon, and the 

 quantitative results obtained are correspondingly high. Our own results 

 with ammonium oxalate solution, contrary to those recorded in the litera- 

 ture on the subject, are hardly ever on the low side ; they average from 

 0-2 to 0-3 per cent, high (Series II. p. S). The possibility of com- 

 pensating errors consisting in the presence of carbon with the deposited 

 metal on the one hand, and the incomplete separation of the iron on the 

 other, has recently been discussed by Avery and Dales ^ and by Verwer 

 and Groll.'- The former find that the deposited iron does contain carbon, 

 on an average 0-21 to 0-42 per cent, on the metal deposited, and that some 

 iron remains in the electrolysed solution. The latter was determined gra-vi- 

 metrically after evaporating the solution and igniting the residue, and in 

 the three experiments made averages 0-35 per cent. The results published 

 from the Aachen laboratory, on the other hand, confirm Classen's original 

 view, that there is no carbon with the deposited iron, and that the iron is 

 completely precipitated. Eight experiments are given by Yerwer and 

 GroU ; the results are all low, a total of 7-6 mgr. of iroii being wanting 

 in the eight experiments. Still, no iron could be detected on evaporating 

 all the solutions left after the electrolysis together, and testing with 

 potassium sulphocyanide or other reagent after ignition and solution. 

 These experiments were conducted with warm solutions, with a C. D. ,gg 



Ber. 1899, 32, 64 and 2233. 



Bar. 1899, 32, 806. 



N 2 



