1813.] 



Imperial Institute of France, 



893 



from which this chemist coDcludes that it is the acid which 

 furnishes oxygen to the iiev/ portion of lead, and that the solution 

 is changed from the state of a nitrate to that of a nitrite, A 

 remarkable property, which serves to distinguish the nitrites of 

 lead from the nitrates, is that of forming in the nitrate of copper 

 a precipitate composed of the hydrate of copper and of lead. 

 By tliese experiments M. Chevreul restores to the yellow oxide 

 of lead the rank of protoxide. 



This chemist has been led to examine in a general manner 

 the salts which lead forms with nitric acid. He has shown that 

 there are two nitrates and two nitrites ; one of which in each 

 class contains twice as much oxygen as the other. He suspects 

 that there exists a third species of nitrite containing four times 

 less oxide than the first. 



Porous bodies absorb gases in different proportions, and 

 charcoal is one of those that absorb the most. The accurate 

 knowledge of the limits of this absorption being important ia 

 chemical operations, M. de Sausstire has lately examined it with 

 much care and success. All cliarcoals have not that property in 

 the same degree, and all gases are not absorbed in the same 

 proportion. The same charcoal will absorb 90 times its bulk of 

 amraoniacal gas, and scarcely 1*75 of hydrogen gas. 



M. Thenard has repeated these experiments with some 

 variations, and has obtained nearly the same results. He has 

 thrown the whole into the form of a table. He has observed, as 

 Saussure and Count Rumford had done in other experiments, 

 that oxygen gas is changed into carbonic acid gas, though the 

 temperature be not hig-fi. Nitrous gas is partly decomposed, 

 and carbonic acid and azotic gas disengaged. But sulphureted 

 hydrogen is the gas the absorption of which presents the most 

 Temarkable phenomena. It is destroyed in a short time, water 

 and sulphur deposited, and so much heat evolved th&c the tem« 

 perature of the charcoal is greatly elevated. 



Jl. Lampadius, a German chemist and philosopher, while 

 distilling iron pyrites with charcoal, had obtained a substance, 

 liquid and volatile, the composition of which was doubtfuL 

 Lampadius himself, and the late M. Amedee Berthollet, consi- 

 dered it as a compound of sulphur- and hydrogen; MM. 

 Clement and Desormes, as a compound of sulphur and charcoal. 

 M. Ciusel, operator of chemistry in the Polytechnic School, 

 wishing to ascertain the nature of this substance, attempted to 

 decompose it by making it pass over plates of copper, in hot 

 tubes ; but this method not having entirely succeeded, he 

 endeavoured to analyse it by means of the Voltaic battery, and 

 after many attempts, dehcate and numerous precautions, and a 

 skilful use of different chemical bodies, he conceives that he has 

 determined its composition as follows 



