1820.] Ferrochyazate of Iron . 223 



The specific gravity of oletiant gas 0'9708 



carburetted hydrogen . . 0*555 



2)1-5258 



Mean specific gravity = 0-7629 



But it will be seen above that the specific gravity of our gas is 

 only 0-6743, which is considerably less than the mean specific 

 o-ravity of such a mixture. We must, therefore, consider the 

 inflammable gas evolved when ferrochyazate of iron is exposed 

 to a red heat as a pecuhar compound, and not a mixture of car- 

 buretted hydrogen and olefiant gases. We may consider it as a 

 compound of equal volumes of these two gases increased in 

 volume about a ninth part. 



Thus we have discovered a new gaseous combination of 

 carbon and hydrogen ; so that the known gaseous combinations 

 of these two substances amount to three. I have little doubt 

 that they will be found hereafter to unite in a still greater num- 

 ber of proportions. Indeed we require a considerable number of 

 additional gases to be able to account for the great variations in 

 the specific gravity and other properties of the combustible gases 

 from coal and other similar bodies. 



Thus it appears that when ferrochyazate of iron is kept at a 

 red heat while air has no access to it, a decomposition takes 

 place, and there are formed 



Water, Supercarburetted hydrogen,* 



Hydrocyanic acid. Azote. 



Ammonia, 



The data which I have stated do not enable us to determine 

 the respective quantities of each of these substances ; conse- 

 quently we cannot determine the nature of the decompositions 

 which take place. Indeed I have no doubt that a portion of 

 ferrochyazic acid, or at least of the iron which exists in that 

 acid, was mixed with the other constituents, though, from the 

 nature of the processes, I had not the means of detecting it. 

 Indeed in one process in which all the liquid products made 

 their way into the jars standing over mercury, traces of prussian 

 blue were visible in the liquid, and the gaseous products, as 

 might have been expected, were reduced in quantity. 



The copious evolution of ammonia, when prussian blue is set 

 on fire, constitutes one of the most curious and instructive 

 phenomena. We see the great tendency, which azote and 

 hydrogen have to unite in the proportions constituting ammonia. 

 1 shall not prosecute this subject further at present ; but as the 

 curious phenomena which appear during the decomposition of 

 the ferrochyazates are by no means exhausted, I may, perhaps, 

 resume the subject hereafter. 



• By this provisional name I mean lo distiognish the new inflamjiiable gas extri. 

 catcd frum prussian blue by licat. 



