Abstract
An internal standard electrode was prepared by packing graphite powder with a definite amouut of internal standard substances into the capillary of a soaking-up electrode. Various method of adding the standard into graphite were examined, amomg which was recommended the following.
The graphite powder was immersed in a nitric acid solution containing zinc (20%) and dried in an electric furnace at about 250°C. Then the powder was packed into the capillary of the electrode and the hydrochloric acid (1 : 5) was soaked up to the top of it. The electrode was heated gently by slowly raising the temperature (the rate should not exceed 50°C/hr.), and kept for 30 min. at 200°C.
Aluminum sample solutions acidic with nitric acid (1 : 2) were soaked up and excited with a. c. intermittent are of 3A. Steady intensity ratios of spectral lines Zn 3072.1Å/Al 3082.8Å were obtained in the range of 1 to 3 min. from the beginning of the excitation.
100 to 500 μg/ ml of Al were determined under these conditions with standard deviations about 15%.
