Chemistry and Physics. 389 



same spectrum ; (3) cyanogen burns with a flame giving a banded 

 spectrum assumed from the foregoing facts to be that of this 

 gas, and (4) this spectrum can be photographed when a con- 

 densed spark is passed between electrodes of gold in an atmos- 

 phere of cyanogen. Hartley has examined this question and 

 concludes that the facts which have been obtained solely from 

 observations on this arc are insufficient to establish the existence 

 of a definite cyanogen spectrum. While certain facts have 

 appeared tending to support the view that the carbon spectrum 

 ought to be given by the flame of burning cyanogen, on the 

 other hand it has been shown that lines somewhat resembling the 

 edges of the cyanogen bands are seen when moistened graphite 

 electrodes in air have sparks passed between them; these lines 

 being intensified if the water used in moistening contains ammo- 

 nium, calcium or zinc chlorides, developing into bands which 

 become stronger as the solution is made more concentrated. 

 This is explained by the fact that all mineral acids contain 

 ammonia, ireshly made sulphurous acid being the only one free 

 from it. Salts of calcium and zinc made with ordinary mineral 

 acids therefore always contain ammonium salts. Consequently 

 if the so-called cyanogen bands are really due to the nitrogen of 

 the ammonia, the spectrum of the graphite electrodes will evidently 

 exhibit the bands more strongly in proportion as the solution 

 used is more concentrated. The following facts are instanced to 

 show that the bands and lines observed are really due to cyano- 

 gen and not to carbon alone : (1) The lines on the edges of the 

 bands in the spectrum of a cyanogen flame coincide exactly with 

 those photographed from a potassium cyanide solution, when the 

 spark is passed in an atmosphere of carbon dioxide or of cyano- 

 gen, or when this spark is passed between gold electrodes in 

 cyanogen gas; (2) the cyanogen spectrum in the flame of burning 

 cyanogen is accounted for because there is excess of the gas 

 present ; and while the temperature of the flame is exceedingly 

 high the gas within it is not in contact with a solid substance, and 

 hence the gaseous compound is heated only to incandescence and 

 immediate decomposition does not occur. — Proc. Roy. Soc, lx, 

 216-221, 1896. G. P. B. 



4. On the Electrolytic Solution and Deposition of Carbon. — It 

 has been noticed already that during the electrolysis of dilute 

 sulphuric acid with carbon electrodes, carbon monoxide and diox- 

 ide appear at the anode along with oxygen. Coehn has observed 

 that by suitably altering the concentration of the acid, the tem- 

 perature and the current density, the electrolysis may be so con- 

 ducted that practically the sole products at the anode are carbon 

 dioxide and monoxide ; the gaseous mixture on analysis giving 

 10 per cent. C0 2 , about 30 per cent CO and one per cent, oxygen. 

 If this operation be conducted at low temperatures, the anode 

 disintegrates and particles of carbon remain suspended in the 

 acid. At high temperatures, the carbon dissolves in the acid, 

 giving a yellowish and finally a reddish brown solution. This 



