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本文研究了用偶氮胂Ⅲ(ASAⅢ)光度法测定超基性岩中微量铬。样品经过氧化钠熔融分解,用盐酸羟胺将铬(Ⅵ)还原。在pH4～6的弱酸性介质中,在加热的条件下,铬(Ⅲ)与ASAⅢ生成组成为1:1的紫色络合物,用硝酸酸化,消除ASAⅢ在此酸度下呈现的紫色,络合物的紫色稳定不变。最大吸收在625nm处,在此波长下摩尔吸光系数为2.5×10~4。检量线范围0～1.6μgml~(-1)。
In this paper, trace arsenazo Ⅲ (ASA Ⅲ) spectrophotometric determination of trace amounts of chromium in ultrabasic rocks. Samples were melted and decomposed by sodium oxide, and chromium (Ⅵ) was reduced with hydroxylamine hydrochloride. In mild acidic medium pH4 ~ 6, under the condition of heating, chromium (Ⅲ) forms a 1: 1 purple complex with ASAⅢ and is acidified with nitric acid to eliminate the purple color of ASA Ⅲ in this acidity. The purple color remains stable. The maximum absorption is at 625 nm, and the molar extinction coefficient at this wavelength is 2.5 × 10 -4. Calibration curve range 0 ~ 1.6μgml ~ (-1).