Cyanogen Flame

The phenomena attendant upon the combustion of cyanogen in a Smithells separator are distinctly beautiful. The Cyanogen Flame, or the flame of cyanogen burning at the nozzle consists of two parts, namely, an inner cone of bright peach-blossom tint, and an outer cone shading off from bright blue to greenish grey. On introducing air into the system, the inner cone diminishes in size and descends the outer tube. Whilst this process of detachment, however, is in progress, the inner cone is seen to be surrounded by a rosy halo, which still adheres to it after the descent, but disappears upon entry of more air, being almost immediately replaced by a blue halo. The whole of this time the outer cone remains unaltered. Further addition of air causes the outer cone to disappear, whilst the inner one now becomes more blue, and its halo acquires a greener tint.

Dixon has shown that the rate of Cyanogen Flame or explosion of cyanogen with oxygen reaches a maximum when the two gases are present in molecular proportions. Further addition of oxygen reduces the velocity, the extra oxygen acting as a diluent, just like a neutral gas, such as nitrogen, might be expected to do. It appears, therefore, that the first product of combustion is carbon monoxide, with liberation of nitrogen.

(CN)₂ + O₂ = 2CO + N₂.

This is the main reaction in the inner cone of peach-blossom tint. It is followed, in the outer cone, by the combustion of carbon monoxide, and the greenish fringe alluded to above is attributed to the presence of small quantities of oxides of nitrogen.