100 Mr, Faraday on new Compounds [Feb. 



These substances generally possess the properties before 

 described, as belonging to the bi-carburet of hydrogen. They 

 all resist the action of alkali, even that which requires a temper- 

 ature above 250° for its ebullition ; and in that point are strongly 

 distinguished from the oils from which they are produced. Sul- 

 phuric acid acts upon them instantly with phenomena already 

 briefly referred to. 



Dr. Henry, whilst detailing the results of his numerous and 

 exact experiments in papers laid before the Royal Society, men- 

 tions in that read Feb. 22, 1821,* the discovery made by Mr. 

 Dalton, of a vapour in oil gas of greater specific gravity than 

 olefiant gas, requiring much more oxygen for its combustion, 

 but yet condensible by chlorine. Mr. Dalton appears to consi- 

 der all that was condensible by chlorine as a new and constant 

 compound of carbon and hydrogen ;• but Dr. Henry, who had 

 observed that the proportion of oxygen required for its combus- 

 tion varied from 4*5 to 5 volumes, and the quantity of carbonic 

 acid produced, from 2'o to 3 volumes, was inclined to consider it 

 as a mixture of the vapour cf a highly volatile oil with the 

 olefiant and other combustible gases ; and he further mentions, 

 that naphtha in contact with hydrogen gas will send up such a 

 vapour ; and that he has been informed, that when oil gas was 

 condensed in Gordon's lamp, it deposited a portion of highly 

 volatile oil. 



A writer in the Annals of Philosophy, N. S. iii. 37, has 

 deduced from Dr. Henry's experiments, that the substance, the 

 existence of which was pointed out by Mr. Dalton, was not a 

 new gas sui generis, " but a modification of olefiant gas, consti- 

 tuted of the same elements as that fluid, and in the same propor- 

 tions, with this only difference, that the compound atoms are 

 triple instead of double :" and Dr. Thomson has adopted this 

 opinion in his Principles of Chemistry. This, I believe, is the 

 first time that two gaseous compounds have been supposed to 

 exist, differing from each other in nothing but density ; and 

 though the proportion of 3 to 2 is not confirmed, yet the more 

 important part of the statement is, by the existence of the com- 

 pound, described at page 96, which though composed of carbon 

 and hydrogen in the same proportion as in olefiant gas, is of 

 double the density .f 



* Philosophical Transactions. 



•f- In reference to the existence of bodies composed of the same elements and iu the 

 same proportions, but differing in their qualities, it may be observed, that now we are 

 taught to look for them, they will probably multiply upon us. I had occasion formerly 

 to describe a compound of olefiant gas and iodine (Phil. Trans cxi. 72), which upon 

 analysis yielded one proportional of iodine, two proportionals of carbon, and two of 

 hydrogen (Quarterly Journal, xiii. 429). M. Serrulas, by the action of potassium upon 

 an alcoholic solution of iodine, obtained a compound decidedly different from the preced- 



