Abstract
The impurities in high purity yttrium oxide, such as sodium, magnesium, calcium, copper, iron, lead and zinc, are detected by emission spectrography among which sodium, magnesium and calcium are determined by flame emission and atomic absorption spectrometry using air-hydrogen flame. The influences of several inorganic acids to be used, some metals and high concentration of yttrium on the determination of sodium, magnesium and calcium are investigated.
On the effects of inorganic acids, the emission and absorption of sodium are almost unaffected except that they are gradually decreased with increasing concentration of phosphoric acid. The absorption of magnesium is almost unaffected by less than 0.1M of hydrochloric acid and nitric acid, but considerably decreased by their 1M. It is considerably decreased by sulfuric acid and phosphoric acid. Inversely, it is increased about 50% by perchloric acid. The emission and absorption of calcium are similar to those of magnesium, but they are more decreased by nitric acid, sulfuric acid and phosphoric acid.
On the effects of metal ions, the emission and absorption of sodium are almost unaffected by yttrium, magnesium and calcium. The absorption of magnesium is almost unaffected by sodium, but increased about 50% by yttrium and calcium. The emission and absorption of calcium are not particularly affected by sodium and less than 100 ppm of magnesium, but they are appreciably decreased at the concentration of 500 ppm of magnesium. The emission is increased in the range of 1 to 1000 ppm of yttrium, and rapidly decreased at the concentration of 5000 ppm of yttrium. The absorption is increased at the concentration of 1 ppm of yttrium, and rapidly decreased with increasing concentration of yttrium.
From the above investigation, it is found that hydrochloric acid or perchloric acid is suitable for dissolving the yttrium oxide sample, and sodium, magnesium and calcium are directly determined in the large amount of yttrium by a standard addition method. A sample of 99.9% yttrium oxide is dissolved in hydrochloric acid and determined by flame emission and atomic absorption methods. 40 to 850 ppm of sodium are determined with coefficients of variation of ±0.8 to ±6.8% by flame emission method and ±0.7 to ±2.9% by atomic absorption method, 1.5 to 4.5 ppm of magnesium with c. v. of ±1.1 to ± 5.0% by atomic absorption method, and 42 to 4200 ppm of calcium with c. v. of ±2.4 to ±6.9% by flame emission method and ±0 to ± 10.7% by atomic absorption method.
