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钢中微量钙的比色法测定,过去已有报导,但手续较繁、不易掌握,有的方法测钙镁合量,测镁后用差减法求得钙含量,结果误差增大,不甚理想。镁的测定方法很多,灵敏度较高的是偶氮氯膦Ⅰ比色法,该方法用于球铁中镁的测定,但因需掩蔽大量铁,显色时取样量也受到限制,用它不经分离铁直接显色测定钢中微量镁还是有一定困难的。鉴于上述原因,本文试验了甲基异丁基酮萃取分离铁,间磺酸基偶氮安替比林比色测定钙,允许锰700μg,镁150μg。偶氮氯膦Ⅰ比色测镁时,加入EGTA—Pb掩敝钙,锰高时可加入邻菲啰啉掩蔽,普通钢中锰不干扰测定。试验结果表明,本方法具有简便,快速、容易掌握、灵敏度高等优点,方法的检测下限为1×10~(-3)％。
The determination of trace calcium in steel by colorimetry has been reported in the past, but the procedure is complicated and not easy to grasp. Some methods measure the amount of calcium and magnesium, and after measuring magnesium, calculate the content of calcium by the subtractive method. The error of result increases, ideal. Many determination of magnesium, the sensitivity is higher chlorophosphorus I colorimetric method for the determination of magnesium in ductile iron, but due to the need to mask a large amount of iron, color sample volume is also limited, with it not Direct separation of iron color measurement of magnesium in the steel or there are some difficulties. In view of the above reasons, this paper tested the extraction of methyl isobutyl ketone iron, m-sulfonic acid azo antipyrine colorimetric determination of calcium, allowing manganese 700μg, magnesium 150μg. Chlorophosphonazo I colorimetric magnesium, adding EGTA-Pb masking calcium, manganese can be added when the adjacent phenanthroline masking, manganese does not interfere with the determination of ordinary steel. The test results show that the method has the advantages of simple, rapid, easy to master, high sensitivity and the detection limit of the method is 1 × 10 -3%.