of certain injlammable gaseous Compounds. 203 



4. T!ie conclusions drawn from the last experiment are founded 

 upon the supposition, that defiant gas is decomposed hy the 

 simple operation of a high temperature, and that one volume is 

 resolved into two volumes of hydrogen, losing at the same time 

 its carbon. The importance of tliis fact, as connected with 

 these researches, induced me to repeat, wiih every requisite pre- 

 caution, the beautiful experiment of M. Berthollet, which con- 

 sists in decomposing this gas by passing it repeatedly through a 

 red hot earthen tube; instead of whicii, however, I employed a 

 lube of platinum, arranged as in the last experiment, increasing 

 the heated surface bv the introduction of quartz crystals. One 

 hundred measures of olefiant gas*, obtained by distilling alcohol 

 with sulphuric acid, were passed and repassed through the tube 

 heated to higli redness, until they ceased to dilate : when the 

 apparatus was cool, the volume of gas was almost exactly doubled; 

 there was a copious deposition of charcoal in the part of the tube 

 that had been ignited, and the evolved hydrogen was so free 

 from carbon, that when detonated with its volume of oxygen, 

 lialf a volume of the latter remained, which scarcely rendered 

 lime water turbid, and underwent no perceptible diminution by 

 exposure to liquid potassa. 



It may be supposed, that in consequence of the dilution of 

 the last portions of olefiant bv the hydrogen evolved, the per- 

 fect decomposition of the gas is a matter of difficulty ; and a trace 

 of carbon will, I believe, always remain in the hydrogen evolved, 

 since the decomposition is progressive. I cannot, however, on 

 this account see reason to believe, with M. Bertholletf, that 

 carbon and hydrogen are capable of forming several definite 

 compounds ; the data are, on the contrary, such as to warrant 

 an opposite conclusion. 



In makinj; this experiment in the manner just described, and 

 more especi lly when the tube is onlv dull red, the first portions 

 of gas that reach the receiving gasometer are obscured by a con- 

 siderable quantity of vapour, which, however, afterwards dis- 

 appeared. To examine more particularly the cause of this 

 phaenomenon, I passed some pure olefiant gas, very slowly, 

 through a red hot glass tube, about two feet in length, and con- 

 taining in the heated part some pure and well burned charcoal : 

 the gas was collected in a cold receiver, tlic sides of which be- 

 came lined with a brown viscid substance of an agreeably liagrant 

 odour, perfectly soluble in alcohol, and precipitated from this so- 



• Tlii>( f^iis was washed with sohition of potassa to separate a little carbo- 

 nic acid, and was then ascertained to be puie by the action of chlorine, wii.ii 

 the precautions afterwards described. 



f Thenard, Traitd de Chimie, torn. I. p. 293. 



C c 2 lutiou 



