Variously treated rotating carbon disk electrodes are tested to improve the precision and sensitivity of emission spectrographic analysis on sulphuric acid solutions of heat resisting steel wires containing Fe, Cr, Al, Mn and Co. The best was found to be paraffin impregnated disk with which the sensitivity increased almost to the same level for all the samples independent of original differences in lots and manufacturers.The increase in photographic density of spectral lines often attained twofold. This treatment also decreased the fluctuation (the variation coefficient) of the density ratio of an element to the internal standard molybdenum, especially for less abundant elements, thus giving good calibration curves. The favorable action of the paraffin impregnation may be attributable to its prevention of sample solution from rapidly diffusing inward, keeping a large and constant amount of it on the disk surface.
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