obtained iii the Decomposition of Oil. 193 



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. DaUon, was 

 not a new gas sui generis, " but a modification of olefiant gas, 

 constituted of the same elements as that fluid, and in the same 

 proportions; with this only difference, that the compound atoms 

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

 this opinion in his Principles of Chemistrj^. This, I believe, 

 is the first time that two gaseous compounds have been sup- 

 posed to exist, differing from each other in nothing but den- 

 sity ; and though the proportion of 3 to 2 is not confirmed, 

 yet the more important part of the statement is, by the ex- 

 istence of the compound described at page 188; which, though 

 composed of carbon and hydrogen in the same proportion as 

 in olefiant gas, is of double the density *. 



It is evident that the vapour observed by Mr. Dalton and 

 Dr. Henry must have contained not only this compound, and 

 a portion of the bi-carburet of hydrogen, but also portions of 

 the other (as yet apparently indefinite) substances ; and there 

 can be no doubt that the quantity of these vapours will vary 

 from the point of full saturation of the gas, when standing 

 over water and oil, to unknown, but much smaller, propor- 



* In reference to the existence of boilies composed of the same elements 

 and in the same proportions, l)ut differing in their qualities, it may be ob- 

 served, that now we are taught to look for them, they will probably mul- 

 tiply upon us. I had occasion formerly to describe a compound of olefiant 

 gas and iodine (Phil. Trans, cxi. ^2), which upon analysis yielded one pro- 



!)ortional of iodine, two proportionals of carbon, and two of hydrogen. 

 Quarterly Journal, xiii. 4:29.) M. Serrnlas, by the action of potassium 

 upon an alcoholic solution of iodine, obtained a compound decidedly dif- 

 ferent from the preceding in its properties ; yet when analysed, it yieldeil the 

 same elements in the same proportions. (Ann. de Chimie, xx. 245; xxii. 17~.) 

 Again : MM. Liehig and Gay-Lussac, after an elaborate and beautiful 

 investigation of the nature of fulminating compounds of silver, mercury, 

 &c., were led to the conclusion that they were salts, containing a new 

 acid, and owed their explosive powers to the facility with which the ele- 

 ments of this acid separated from each other. {Annales de Chimie, xxiv. 

 iiD4; XXV. 2S5.) The acid itself, being composed of one proportional of 

 oxygen, one of nitrogen, and two of carbon, is equivalent to a proportional 

 of oxygen + a proportional of cyanogen, and is therefore considered as a 

 true cyanic acid. But M. Wohler, by deflagrating together a mixture of 

 fe.TO-prussiate of potash and nitre, has formed a salt, which, accordinrr to 

 his analysis, is a true cyanate of potash. The acid consists of one propor- 

 tional of oxygen, one of nitrogen, and two of carbon. It may be transferred 

 to various other bases ; as the earths, the oxides of lead, silver. Sec. : but the 

 salts formed have nothing in common with the similar salts of MM. Liebig 

 and Gay-Lussac, cxce|)t their composition. (Gilbert's Aimalcn, Ixxviii. l.ij 

 Ann. de Cliimw, xxvii. 190.) M. Gay-Lussac observes, that if the analysis be 

 correct, the difference can only be accounted for by admitting a different 

 mode of combination. 



Vol. 66. No. 329. Sept. 1825. B b tlons. 



