300 BALARD’S RESEARCHES CONCERNING THE NATURE OF 
have been furnished by the chlorous acid. The latter was therefore: 
manifestly composed of two volumes of chlorine and one volume of 
oxygen. 
I was however apprehensive that one circumstance might Contribute: 
to render this mode of analysis imperfect, which however appeared 
to me as simple as it is elegant. It was, in fact, possible that the heat 
generated might disengage a portion of the chlorous acid in the gas- 
eous state, which, as I have already stated, is completely absorbable by 
mercury. The gas then obtained would have contained something be- 
sides chlorine, and the volume of this gas elicited would not then have 
been rigorously equal to that of the hydrochloric acid employed. 
When also I had afterwards observed that concentrated sulphuric 
acid, in acting upon liquid chlorous acid, disengaged from it, if not pure 
chlorous acid, at least the gaseous products of its decomposition, I de- 
termined to ascertain in what proportion they contained chlorine and 
oxygen. 
For this purpose, I submitted 50 volumes of this gas to the action of 
heat, in order to effect its detonation. I thus obtained 72 volumes, 
which treated with an alkaline solution were reduced to 25 volumes 
of oxygen gas. If it be considered that in this mode of experimenting a 
small portion of chlorine is necessarily absorbed by the mereury, the 
slight loss sustained will be readily explained ; and, as it appears to me, 
it will be concluded that this experiment proves, as well as the former 
ones, that chlorous acid is composed of two volumes of chlorine and one 
volume of oxygen. 
When the methods which I have described allowed of my procuring 
pure chlorous acid, I confirmed the previously obtained results by direct 
analysis. By the detonation of 45 volumes of this gas I procured 69 
volumes of a gaseous mixture, which was reduced to 23 volumes when 
I agitated it with an alkaline solution. This last experiment, not only 
justifies the results with which other methods had already furnished me, 
but allows of appreciating the contraction which the chlorine and oxygen 
undergo in combining to form chlorous acid. It will be observed, in 
fact, that this contraction is one third of the whole volume, and equal 
to that of the oxygen which enters into its composition. The number 
67:5, the product of 45 by 1°5, differs too little, it appears to me, from 
the number 69 which I obtained, to allow of any doubt remaining in 
this respect. 
The analysis of chlorous acid thus shows that 't is formed of the same 
elements and in the same proportions as the gas obtained from chlorate 
of potash and hydrochloric acid, a gas which chemists have long consi- 
dered as protoxide of chlorine. If it were satisfactorily demonstrated 
that this product is really a distinct compound, as it differs much from 
