Fusion of Carbon

IN the course of an investigation on the behaviour of the carbon arc in various gases at high pressure, carried out in apparatus provided by Imperial Chemical Industries Ltd., we have obtained large amounts of carbon in a fine state of division. In certain circumstances this carbon is deposited as graphite, all in the form of small spherules of about 0.02 mm. diameter or smaller, having a density 2.25. There seems to be little doubt that these spherules of graphite have been formed owing to the effect of surface tension, the carbon having persisted for a finite time in the molten state. The best yield was obtained at 90 atmospheres in hydrogen with an arc dissipating 20 kilowatts. The temperature of the positive crater at this pressure has not yet been determined. The surface brightness at 10.5 atmospheres was 2.18 times that of the arc at atmospheric pressure for the same wave-length, corresponding to an increase of brightness temperature of 460°. The increase in the thermodynamic temperature must be of the same order, so that the temperature was probably much higher at 90 atmospheres. Further investigations are necessary before the precise conditions under which the spherules are formed are established. The percentage of ash left after burning the carbon of the electrodes was 0.8, that from the carbon collected from the arc chamber less than 3 per cent. It is scarcely likely that this amount of fusible ash could cause the whole of the carbon to adopt spherical form.