NATURE OF THE BLEACHING COMPOUNDS OF CHLORINE. 285 
with the metal, which it converts into a liquid of deep yellow colour, 
which is acid but does not decolorize ; it appears to be perchloride of 
iron ; it does not seem to be mixed with chlorate. We might be tempted 
to suppose that the action of chlorous acid on other metals is compara- 
ble to that which it exerts upon iron; but this is not the case. The 
greater number of the other metallic substances, put into contact with 
chlorous acid, cannot decompose it, and I am yet entirely ignorant of 
the cause of the peculiarity of iron in this respect. 
Tin filings may remain in contact with weak chlorous acid for 
several days, without causing it to undergo any sensible decomposition, 
and without losing their metallic lustre. The same is the case with 
zinc, with fragments of antimony, bismuth, and lead. But the presence 
of another acid renders these metals capable of effecting this decompo- 
sition. 
The nature of the acid employed for this purpose is not a matter of 
indifference. This acid must form a compound, soluble in water, with 
the oxide of the metal employed. Thus with zine and tin, sulphuric 
acid causes the decomposition of the chlorous acid most rapidly ; with 
antimony, sulphuric acid and even nitric acid does not answer, but 
tartaric acid succeeds extremely well in causing its oxidation; lastly, 
chlorous acid, which alone or mixed with sulphuric acid scarcely acts 
upon lead, exerts an intense action upon it when mixed with a little 
nitric or even acetic acid. 
In this re-action, induced by the presence of these acids mixed with 
the chlorous acid, the metal, in order that it may saturate them, must 
decompose the acid, and not the water; for in combining with the 
oxygen, it is chlorine, and not hydrogen, which it sets at liberty. How- 
ever when in operating with chlorous and sulphuric acid on zine or 
tin, the gas obtained contains a little hydrogen, which indicates that 
in some cases it is at the expense of the water itself that the oxidation 
occurs. 
If concentrated chlorous acid be used, the action is not at first 
more energetic, but it becomes so at the end of a certain time. During 
its spontaneous decomposition chlorous acid forms chloric acid, the 
mode of action of which is the same as that of sulphuric, nitric, and 
other acids, as I determined by direct means. 
Gold and platina do not appear to suffer any action by chlorous 
acid, either alone, or mixed with nitric and sulphuric acid ; but copper, 
mercury, and silver decompose it, and each with a peculiar mode of ac- 
tion. Copper filings put into contact with chlorous acid are partly 
dissolved: the solution after some time is found to contain chloride 
of copper. There is also formed at the same time a green powder, 
which appears to be merely oxichloride of copper, and it disengages 
chlorine mixed with a very small proportion of oxygen. 
