4^0 
Mr, Faraday on new compounds 
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 por- 
tions 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 
* 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 observed, that now w'e 
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 §ame 
elements in the same proportions, (Ann. de Chimie, XX. 245, XXII. 172). 
Again. MM. Liebig and Gay Lussac, after an elaborate and beautiful investi- 
gation 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 explo- 
sive 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 com- 
posed of one proportional of oxygen, one of nitrogen, and two of carbon, is equiva- 
lent 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 ferro-prussiate of potash and nitre, has formed a salt, which, ac- 
cording to his analysis, is a true cyanate of potash. The acid consists of one pro- 
portion 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. j but the salts 
formed have nothing in common with the similar salts of MM. Liebig and Gat 
Lussac, except their composition, (Gilbert’s Annalen, LXXIII. 157. Ann. 
de Chimie, XXVII. 190). M. Gay Lussac observes, that if the analysis be cor- 
rect, the difference can only be accounted for by admitting a different mode of 
combination. 
