148 
IOWA ACADEMY OF SCIENCES. 
solution of ferrous sulphate. Carnot * reduced the chlo- 
rates in bleaching powder by heating at 100° and in the 
presence of sulphuric acid with about twenty times the 
theoretical amount of ferrous ammonium sulphate. The 
amount of chloric acid was found either by titrating 
the resulting chloride by Volhard’s method or by titrating 
the excess of ferrous sulphate with potassium permanga- 
nate. Rosenbaum f states that chlorine will be lost in 
this method of reduction if the acid and ferrous sulphate 
are added to a hot solution of the chlorate. 
In the course of my own work on the action of chloric 
acid on metals, it was observed that metallic iron very 
readily reduces chloric acid even in very dilute solutions. 
At ordinary room temperature the solution of the metal is 
very rapid in moderately concentrated solutions, and in 
any case the iron goes at once into the ferric condition, as 
was proved by many tests while solution was going on. 
No gas is evolved, but the iron simply disappears and there 
results the yellowish-brown solution of a ferric salt, if the 
acid is in excess. Whether iron alone reduces chloric acid 
completely could not be determined owing to the large 
amount of iron oxide, and possibly insoluble basic salt, 
which were formed, and which made it impracticable to 
obtain a solution suitable for titration with silver without 
the use of a reducing agent and sulphuric acid. An 
•approximation, however, showed that about 95 per cent of 
the chloric acid w r as reduced. 
These facts suggested that the determination of chloric 
acid might be brought to a very simple form by using 
metallic iron as the chief reducing agent in the presence 
of an excess of sulphuric acid, which would prevent the 
formation of insoluble compounds, make the method 
applicable to chlorates by setting free the chloric acid, and 
form ferrous sulphate which is itself a reducing agent , for 
chlorates, and which would already be present to serve 
when oxidized as the indicator in the titration of the 
chloride by the method of Volhard. It is evident, there- 
*<''omp\ Rend., 122, 449 and 452 
f Zeit. d. Angew. Ohem. 18yi3, 80. 
