294 balard's researches concerning the nature of 



course to nitrate of lime, a very deliquescent calcareous salt, the action 

 of which changed my idea on the subject. 



When a mixture is made of nearly equal volumes of concentrated 

 liquid chlorous acid, and very dry solid nitrate of lime, a brisk effer- 

 vescence ensues, and a gas is produced, which re-dissolved in water 

 gives a product possessed of all the properties of liquid chlorous acid, 

 and which ought consequently to be considered as pure chlorous acid 

 gas. The same results are obtained by using vitreous phosphoric acid* 

 instead of nitrate of lime. 



If an attempt be made to collect chlorous acid gas in the mercurial 

 trough in the usual way, the metal is attacked, and oxygen alone re- 

 mains ; sometimes indeed the absorption is complete. It is then neces- 

 sary, in order to obtain it, to operate in a peculiar manner. The fol- 

 lowing method has alA^ays succeeded. 



After having introduced into a receiver filled with mercury about 

 -yVth of its volume of concentrated chlorous acid, I gradually passed up 

 fragments of dry nitrate of lime. The gas is disengaged with effer- 

 vescence, and, as it does not touch the mercury, being separated from 

 it by the solution of nitrate of lime, it may be kejit in the trough for a 

 long time. Afterwards it may be transferred from one receiver to an- 

 other, provided this operation be effected rapidly ; for it is but slightly 

 decomposed by the metal, when it passes through it in large bubbles. 



Chlorous acid gas is of a yellow colour, and but little deeper than 

 that of chlorine, with which in the course of my researches I had long 

 confounded it, on account of this similarity of tint. Its smell is ex- 

 tremely pungent, and like that of the liquid acid ; it is completely ab- 

 sorbable by mercury, which it converts into red oxichloride. 



Water dissolves many times its volume. I have not determined this 

 solubility very exactly, but I believe it to be more than 100. The so- 

 lution is very slightly coloured, and has the properties of liquid chlo- 

 rous acid. The solution of chlorous acid in water takes place very 

 rapidly, but there always remains, after the operation is over, a very 

 small residue of chlorine and oxygen, which indicates a very slight de- 

 composition of this gas during its preparation. A small increase of 

 temperature separates its elements with explosion, and a very conside- 

 rable disengagement of heat and light. Although it appears to me 

 more difficultly decomposable by increase of temperature than the ox- 

 ides of chlorine, it has happened to me that it has exploded during 

 transfer. On this account, care should be taken to add the nitrate of 



• Care mnst be taken to use phosphoric acid which is not prepared by the de- 

 composition of phosphate of ammonia by heat. As this often retains a little 

 ammonia, it produces chloride of azote, which, by the slightest increase of tem- 

 perature, gives rise to detonations, which are the more dangerous as not being 

 foreseen. 



