As the tin content in the enriched layer of steel was expected to vary within a wide range of 0.02 to 30 per cent, the range was devided into three parts and the analytical conditions were studied for each of them. Because of the large gradient of the concentration of tin in the layer, care was taken to make the depth of the crater of the discharge as small as possible. An intermittent arc was used to analyze the range of 0.02 to 0.4 per cent tin. It was found that the arc discharge employed consisted of a train of discharges of short duration, flushing once per cycle of line voltage, and at the beginning of the discharge each short discharge was liable to go to the different parts of surface of the sample leaving an equal number of tiny and shallow craters, but after 20 cycles or more the crater began to overlap one another, so after 20 cycles each the sample was moved a bit laterally, and the depth of crater was thus kept within 0.011 and 0.018 mm. A Feussner spark was applied to analyze the tin over 0.3 per cent. Both the prespark and exposure times were reduced as much as possible, so that the depth of the crater was 0.009 mm for medium (up to 2 per cent) concentration, and 0.002 mm for high concentration. The sparking curves were found different in form according to the concentration of tin.
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