ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Some physical properties of carbon electrodes for spectral analysis

E. Plško

Slovak Academy of Sciences, Bratislava

Abstract: The d.c. arc characteristics of 13 electrodes of different manuf. were compared. The current, voltage, and radiation intensity (detd. with a vacuum thermocouple) were measured with mirror galvanometers and recorded photographically as functions of time. The distance d between electrodes, which began as 1 mm. and increased with time, was detd. from an enlarged image of the arc projected on a mm. scale, and also recorded as a function of time. Curves of elec. and radiation characteristics were then plotted against d. The stability of the arc was followed with a gas-filled photocell registering on an oscillograph screen, which was photographed on moving film. The elec. resistance and x-ray powder diagrams of each electrode were also obtained. The electrodes ranged from strongly cryst. (graphitic) to nearly amorphous. The elec. resistance decreased and the heat cond. increased with increasing crystallinity. Nineteen operating characteristics, such as the elec. conditions and electrode distance when the are was extinguished, the time of burning, elec. conditions at d = 7 mm., conditions at the transition from a noisy to a silent arc, and the time to reach max. emitted energy, were calcd. and correlated with the elec. resistance and crystallinity for all electrodes. E.g., with increasing elec. resistance, the max. resistance of the arc when extinguished increased, d at the transition to a silent arc increased, and the transition was more gradual. The characteristics of an ideal graphite electrode are listed. The results make possible quality control of the manuf. of electrodes.

Full paper in Portable Document Format: 156a404.pdf (in Slovak)

Chemical Papers 15 (6) 404–413 (1961)