1896.] Hypochlorites to Chlorates. 79 



From the above it is evident that a solution of sodium hypochlorite 

 slowly decomposes even when kept in absolute darkness. The rate of 

 decomposition increases with the refrangibility of the rays. Yellow 

 rays are far more powerful than red rays. The transformation is one 

 into chlorate and free oxygen. 



The experiment was repeated with a 5 per cent, solution of sodic 

 hydrate. It was saturated with chlorine and the excess of chlorine 

 carefully removed by bubling dry air (free from carbonic acid) through 

 the solution. A solution of hypochlorite containing free alkali was then 

 cautiously added drop by drop so long as the smell of chlorine persisted. 

 Non-existence of free chlorine was proved by the mercury reaction. 

 The solution was so unstable that no systematic experiment was found 

 possible. In the course of an hour it changed its titre by several per- 

 cents. It was kept in a brown stoppered bottle in the dark room. 

 After some three hours the stopper was removed, when a distinct smell 

 of chlorine was perceived. The liberation of chlorine increased with 

 time, but there seemed to be a limit. On shaking, however, the smell 

 very nearly disappeared, but the absorption of chlorine by the free 

 alkali which must have been simultaneously formed was never complete. 

 The behaviour of sodium hypochlorite in aqueous solution is very 

 peculiar. Under ordinary circumstances in presence of free alkali it 

 decomposes into free oxygen and a chloride, a chlorate being at the 

 same time formed. In the other case it seems to dissociate into free 

 chlorine and free alkali. 



Influence of pressure. 



The action of pressure on a solution of sodium hypochlorite is 

 interesting. Minute bubbles of oxygen are given up when diffused light 

 acts on it for some time. Since sodium hydrate dissolves notable quan- 

 tities of free oxygen, these bubbles are not seen until after some time. 

 When, however, a tube containing some of the above solution is exhaust- 

 ed of air (pressure 5-6 cm. of mercury) the decomposition is accelerated 

 and a regular evolution of oxygen begins, so much so as to render the 

 solution slightly milky. 



Transformation in the dark at a temperature op 100° C. 



The methods adopted in these experiments were very nearly identi- 

 cal with the previous ones. The tubes were, however, stouter, as a good 

 deal of internal pressure was produced in some of these experiments 

 owing to the generation of a comparatively large volume of gas. In 

 fact, when the duration of heating was prolonged to some fifteen to 

 twenty hours, some of the tubes exploded, thus rendering a whole set 



