246 On the Oxidation of Ferrous Salts 



the volume to about 60 c.c., then titrated with permanganate in 

 hydrochloric 'acid solution, with the addition of enough ferri- 

 ryanide to colour the solution blue. 



From this table it will be seen that with 10 c.c. fuming 

 hydrochloric acid the results are quite as good as with sulphuric 

 acid. With 25 c.c. hydrochloric acid the method becomes a 

 little strained ; but it can be perfectly well carried out if care 

 is taken to add the permanganate slowly so as to avoid a local 

 excess, which would involve oxidation of the hydrochloric 

 acid. This happened in experiment No. 6. In No. 5, which 

 was also otherwise unsatisfactory, the ferricyanide had produced 

 a precipitate which should always be avoided. 



In Table II will be found the results of experiments on the 

 action of chlorate of potassium and of perchlorate of potassium 

 solutions on ferrous sulphate in sulphuric acid and in hydro- 

 chloric acid solution when left together for a short time. 



TABLE II. 



In ( xperiments n and 13 the chlorate of potassium solution 

 used was not that described above, which is used for all the 

 following experiments, but a somewhat weaker one, of which 

 14-2 c.c. were required to oxidise o-i gramme of iron. It will 

 be seen that the only case which shows any decomposition is 

 No. n, where n-o instead of 11-2 c.c. permanganate have 

 been used. Hence at ordinary temperatures the action of 



