182 



REPORT — 1900, 



and IV., in which ;") gr. of ammonium oxalate were used, should be 

 0'7 mgr. too high from this source of error. In the two sets of experi- 

 ments the values obtained average an excess of 0'2 mgr., and the weight 

 of metal remaining in solution after the determination is 0'2 to 0"3 mgr. 

 These compensating errors, therefore, contribute to the apparent accuracy 

 of the method ; they are sufficiently small to bring the process witliin 

 the range of practical analysis. This conclusion is in accoi'd with the 

 experiments recorded by Avery and Dales ; the difference in the Tper- 

 centage of carbon found is in all probability due to the time of electro- 

 lysis. It is impossible to reconcile these results with those of Verwer 

 and Groll ; but that their results, like those obtained by Classen, are low 

 is undoubtedly to be attributed to the method adopted for testing the 

 completion of the deposition of iron by means of potassium sulphocyanide. 

 The origin and direction of the eri'ors arising in the electrolysis of 

 ammonium oxalate solutions containing iron are clearly shown by our 

 experiments, and it is unlikely that different conditions prevail when 

 other metals are present in the same electrolyte. The facts thus esta- 

 blished must be duly considered in judging of the results obtained by these 

 methods, especially in such cases as atomic weight determinations. 



The quantities of carbon deposited with the iron were too small to 

 allow of the investigation of its condition of combination. We are, how- 

 ever, inclined to think that it is present as a carbide, for whenever the 

 deposited metal is dissolved in acid the smell of hydrocarbons can always 

 be noticed ; also, after the upper layer of the metal has dissolved, the 

 underlying portion is very often darker in colour and more difficult to 

 dissolve. 



5. T/ie Electroljitic Separation of Iron and JMwnganese in Ammovium Oxalate 

 Sohctio7i. By Charles A. Kohn, M.Sc, Ph.D., and H. H. Frotsell. 



Bihliogrupliy . 



