428 COMPOUNDS OF CARBON. 



of potassium and 1 of carbonic acid, which combine respectively 

 with bisulphuret of carbon and potash. 



Solid sulphuret of carbon. The charcoal left in the tube, 

 after the process for the former compound, is much corroded, 

 and contains a portion of sulphur which cannot be expelled 

 from it by heat. Berzelius is disposed to consider this sulphur 

 as in chemical combination with the carbon. 



SECTION III. 

 CARBON AND NITROGEN. 



Bicarburet of nitrogen, or cyanogen, N C 2 . This compound 

 is a gas, which was first obtained by Gay-Lussac in 1815. It 

 is prepared by heating the cyanide of mercury in a small glass 

 retort, and is collected at the mercurial trough. The cyanide is 

 resolved into running mercury and cyanogen gas, and frequently 

 leaves a black coaly mass in the retort, which Professor John- 

 ston has shown to consist of carbon and nitrogen, in the same 

 proportions as the gas itself. 



Cyanogen gas contains 4 volumes of carbon vapour and 2 

 volumes of nitrogen, condensed into 2 volumes ; its density is 

 J819. When this gas is exploded with twice its volume of 

 oxygen, it affords 2 volumes of carbonic acid gas, and 1 volume 

 of nitrogen, an experiment from which its composition may be 

 deduced. Water at 60 absorbs 4.5 times its volume of this 

 gas, and alcohol 23 volumes. By a pressure of 3.6 atmospheres 

 at 45, cyanogen is condensed into a limpid liquid, which eva- 

 porates again on removal of the pressure. Cyanogen burns 

 with a beautiful purple flame in air or oxygen. The solution of 

 cyanogen in water undergoes spontaneous decomposition. By 

 alkalies the gas is absorbed, and a cyanide and cyanate formed. 



Cyanogen is a salt-radical, and unites with all the metals, as 

 chlorine and iodine do, forming a class of cyanides. It also 

 forms a hydrogen acid, namely, prussic or hydrocyanic acid. 

 Cyanogen properly belongs to organic chemistry, in which de- 

 partment its numerous combinations will be considered. 



Mellon, N 4 C 6 . This is another salt-radical, and was formed 

 by Liebig by heating the bisulphuret of cyanogen to redness, 

 when it is resolved into sulphur, bisulphuret of carbon, and 

 mellon. It is a lemon yellow powder, insoluble in water and 

 alcohol. It unites directly with hydrogen and with potassium, 

 forming hydromellonic acid and mellonide of potassium. 



