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新显色剂偶氮硝膦I[2-(4-硝基-2-膦酸苯偶氮)-1,8-二羟基-3,6-萘二磺酸]能在硼砂氢氧化钠体系中,pH8.6～9.35范围内与镁迅速发色,形成兰色络合物.络合物至少稳定8小时.该络合物具有高的灵敏度(ε_(580)=3.85×10~4l·mol~(-1)cm~(-1))、较宽的比耳定律范围(0～30μgMg/25 ml).用等克分子连续变更法及摩尔比法测得络合物组成为R∶Mg=1∶1. 由于显色反应中共存离子干扰较小,并允许一定量的掩蔽剂(如三乙醇胺、邻菲罗啉等)存在,故该试剂的选择性较其它同类试剂为优. 本文报导了用NPA-I不经分离测定微量镁简单、迅速、准确的方法.分析结果证明,本法用于某些球墨铸铁和稀土-硅-镁中间合金,取得了满意的结果.
A new chromogenic reagent nitroazo I [2- (4-nitro-2-phosphonophenylazo) -1,8-dihydroxy-3,6-naphthalenedisulfonic acid] in borax sodium hydroxide system In the range of pH 8.6 ~ 9.35 with magnesium rapidly to form a blue complex.The complex is stable for at least 8 hours.The complex has high sensitivity (ε 580 = 3.85 × 10 -4l · mol -1 cm -1) and a wide range of Beer’s Law (0 ~ 30 μg Mg / 25 ml) .The composition of the complex was determined by the method of continuous modification by the same molecule and molar ratio Mg = 1: 1. The selectivity of this reagent is superior to other similar reagents due to the small interference of coexisting ions in the chromogenic reaction and allowing a certain amount of masking agent (such as triethanolamine, o-phenanthroline, etc.) to exist. In this paper, a simple, rapid and accurate method for the determination of trace amounts of magnesium without NPA-I has been reported.The results show that this method has been applied to some ductile cast iron and rare earth-silicon-magnesium master alloys with satisfactory results.