BLEACHING COMPOUNDS OP CHLORINE. 
301 
tures of chlorides and hypochlorites, and that it is to the latter 
they owe their principal properties. But this result should no 
more induce us to suppose so, than the precipitation of iodine 
by a weak acid, from a mixture of iodide of potassium and 
iodate of potassa, should authorize us to confound a colourless 
solution of such a mixture, with an iodide of oxide distinguish- 
ed from it by colour independent of other properties. 
The hypochlorites even when mixed with metallic chlo- 
rides, may easily be distinguished from the chlorides of oxides, 
by their easy decomposition with evolution of oxygen, when 
heated even slightly;* this gas is never given off when chlo- 
ride of potassa is boiled. The latter supports without decom- 
position a temperature of 50° or 60° Cen., and if it does not 
contain an excess of chlorine, it may even be heated beyond 
80° Cen. without alteration. The hypochlorites have little sta- 
bility, and in summer a few days suffice for their spontaneous 
decomposition; the chlorides of potassa and soda on the con- 
trary may be preserved a long time if kept from the air and 
light. 
The chlorides of potassa and soda, with excess of chlorine, 
prepared by passing chlorine through the alkaline solutions 
until it is no longer absorbed, possess a remarkable property 
which has not yet been noticed, and which cannot well be ex- 
plained on the supposition of their being mixtures of chlorides 
and hypochlorites. When their solutions are boiled in a dis- 
tillatory apparatus, they are decomposed, do not evolve oxy- 
gen or even a notable quantity of chlorine, but hypochlorous 
acid, which with the vapour of water is condensed in the re- 
ceiver. This liquid possesses all the properties of Balard's 
hypochlorous acid; it has the same odour; bleaches, decom- 
poses oxalic acid at low temperatures, with evolution of car- 
bonic acid, liberates chlorine from chloride of sodium, and has 
the same action on iron filings as Balard's acid. The products 
of the distillation should be divided; the liquid first condensed, 
appears to contain free chlorine; the liquid whose properties 
I have just stated, is next obtained. The process should be 
* Balard, Ann. de chi. et de phys. vol. 57. p. 299. 
