1825.] obtained by the Decomposition of Oil. 169 



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, con- 

 stituted of the same elements as that fluid, and in the same pro- 

 portions ; with this only difference, that the compound atoms 

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

 this opinion in his f Principles of Chemistry.' This, I believe, 

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

 posed 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 compound described at page 163 ; 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 



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

 and in the same proportions, but differing in their qualities, it may be ob- 

 served, 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 preceding in its 

 properties; yet when analysed, it yielded the same elements in the same 

 proportions (Ann. de Chimie, xx. 245 ; xxii. 172). 



Again: MM. Liebig 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 elements of this acid 

 separated from each other (Annales de Chimie, xxiv. 294 ; xxv. 285). 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 ferroprussiate of potash and nitre, has 

 formed a salt, which, according to his analysis, is a true cyanate of potash. 

 The acid consists of one proportional 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, &c, ; but the salts formed have nothing in common with 



