M. Gay-Lussac on the Reciprocal Decomposition of Bodies. 117 



compounds (chlorurets and nitrates) which are not analo- 

 gous, and the law, to which we have alluded, cannot apply, 

 to them, except by regarding them without distinction, 

 while in solution, either as chlorurets or hydrochlorates, which 

 is not always the case. 



Sulphuric acid, at the common temperature, separates in 

 part the boracic and arsenic acids from their combinations ; 

 but, at a high temperature, on the contrary, it is separated by 

 those acids. 



The nitric and hydrochloric acids decompose the fluorurets; 

 and, in its turn, the hydrofluoric acid decomposes the nitrates 

 and the chlorurets. 



The acetic acid decomposes several chlorurets, and recipro- 

 cally the hydrochloric acid decomposes the acetates. Many 

 other vegetable acids, and particularly the lactic acid, give rise 

 to analogous phenomena. 



Gases that dissolve in water, and which escape from it in a 

 vacuum, are all separated from that liquid by another gas, 

 when passed through it in excess. 



A number of similar facts might be adduced, but it will 

 suffice to mention the decomposition of the hydro-sulphates by 

 carbonic acid, and that of the carbonates by the hydro- 

 sulphuric acid, on which M. Henry junior has made a very 

 long investigation, to determine facts which might have been 

 easily foreseen by reasoning upon the laws established by Ber- 

 thollet. 



The bicarbonate of potash, for example, exposed in solu- 

 tion to the air, loses a portion of its acid, and acquires the 

 property of precipitating the sulphate of magnesia. If a 

 stream of hydrosulphuric acid gas be passed through it, 

 whose acid properties are known to be nearly the same as 

 those of carbonic acid, a portion of carbonic acid will ne- 

 cessarily become free ; and as it will be removed at the 

 same time by the stream of hydrosulphuric gas, the bicar- 

 bonate will be always exposed to the same causes of decompo- 

 sition, and will by degrees be completely decomposed. 



In like manner, on passing a stream of carbonic acid into a 

 bi-hydrosulphate, partial decomposition of that salt will en- 

 sue, and the hydrosulphuric acid gas, so' separated, being car- 



