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 Avas 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 clilorine 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 mercury, 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 ray 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, diff'ers 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 froro 



