S02 Tfoceedlngs of Philosophical Societies » [May, 



inconsistent with the opinion of Dalton^ who considers cxycar- 

 bureted hydrogen as a mixture of carbonic oxide gas and carbu- 

 reted hydrogen gas ; for in order to explain this experiment by 

 the hypothesis of Dakon wj8 must ascribe all the changes which 

 heat produces upon oxycarbureted gas to the carbureted hydro- 

 gen which it contains, which is very difficult, M. Berthollet 

 having proved by a direct experiment that hydrogen has no action 

 on carbon. 



M. Thenard has made very singular experiments on ammo- 

 niacal gas, nearly inexplicable in the present state of chemistry. 

 If we expose this gas in a state of purity to heat in a close por-. 

 celain tube, very little of it undergoes decomposition ; but the 

 decomposition goes on very rapidly if we put into the tube 

 iron, copper, silver, gold, or platinum. These metals undergo 

 a change in their physical qualities, but neither increase nor 

 diminish in weight, neither take from nor give out to the ga§ 

 any thing ponderahle. Iron possesses this property in the highest 

 degree. All the other metals (except the five above-mentioned) 

 are destitute of the property altogether. This gas decouiposed 

 by this singular method consists of three measures of hydrogen 

 to one of azote. Sulphur and charcoal likewise decompose 

 ammonia ; but form with its elements new combinations. 



A metal cannot be dissolved in an acid without being oxydated. 

 Sometimes it takes the oxygen from the acid itself, sometimes 

 from water. It sometimes happens that a solution saturated with 

 a metal in an acid, when assisted by heat, is capable of dissolv- 

 ing a new portion of the metal? Proust discovered this to be 

 the case with the nitrate of lead. In this case is it the acid or 

 the oxide which furnishes oxygen to this new portion of metal? 

 M. Proust and Dr. Thomson, who repeated his experiments, 

 thought that the oxygen came from the oxide; from which it 

 would result that the whole of the lead thus dissolved v/ould 

 4:ontain a smaller portion of oxygen, or, in other terms, that it 

 would be less oxydized than the oxide which enters into the 

 common nitrate of lead, which is the yellow oxide.* 



But M. Chevreul, assistant naturalist to the Museum of 

 Natural Bistoryj having again examined this question, found 

 that nitrous gas disengaged v.'hen new lead is dissolved in this 

 way, which could not happen unless the nitric acid lost oxygen | 



* Cuvier here states the very opposite of the opinloji which I jrav<^ in my 

 paper on tlie Oxides of Lead, My object was to show that there is no oxide 

 of lead containing less oxygen than the yellow. In the next edition of my 

 Systenx of Chemistry I expressed myself with hesitation on the subjrct, because 

 Cehlen, in his German translation of my pnper, had afDrmed, that by repeat- 

 ing my experiments ©n a greater scale he had detected an oxide coDtainin,^ l*ss 

 - ?&xygen than the 3'ellow,., T, T. 



