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yuyukkll

金虫 (初入文坛)

[求助] EDTA 滴定碱土金属限度 加入硫酸锌的作用是什么?

标定氯化钠的镁和碱土金属限度,为什么要加入硫酸锌?

To 200 mL of water add 0.1 g of hydroxylamine hydrochloride, 10 mL of pH 10.0 ammonia–ammonium chloride buffer, 1 mL of 0.1 M zinc sulfate, and 0.15 g of eriochrome black T trituration. Heat to 40 ℃. Titrate this solution with 0.01 M edetate disodium VS until the violet color changes to deep blue. To this solution add all sample solution. If the color changes to violet, titrate the solution with 0.01 M edetate disodium VS to a deep blue endpoint.
把0.1 g盐酸羟胺,10 mLpH 10.0 铵-氯化铵缓冲液,1 mL 0.1 M硫酸锌和0.15 g研铬黑T研磨物加入200 mL水中。加热至40℃。用0.01 M的乙二胺四乙酸二钠滴定液滴定至紫色变为深蓝色。把配制的样品溶液全部加入溶液中。如果颜色变为紫色,则用0.01 M的乙二胺四乙酸二钠滴定液滴定至紫色变为深蓝色。

Acceptance criteria: NMT 100 ppm, calculated as Ca, (that is the volume of 0.01 M edetate disodium consumed in the second titration does not exceed 2.5 mL).
接受标准:以钙计,不超过100 ppm,(即:第二步滴定消耗的0.01 M的乙二胺四乙酸二钠滴定液体积不超过2.5 mL)。

方法来源,USP
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yuyukkll

金虫 (初入文坛)

加Zn-EDTA我还可以理解,让显色更灵敏。加Zn2+到溶液里面是为了什么呢???难道不会干扰测定吗?
2楼2017-07-12 13:30:39
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