USP 30中，磷酸三镁有这么一项指标：

Dibasic salt and magnesium oxide- Ignite about 2.5g to constant weight. Weigh accurately about 2g of ignited salt, and dissolve it by warming with 50.0 mL of 1N hydrochloric acid VS. Cool, add 1 or 2 drops of methyl orange TS, and slowly titrate the excess 1N hydrochloric acid VS with 1N sodium hydroxide VS to a yellow color, vigorously shaking the mixture during the titration. Between 14.8 and 15.4mL of 1N hydrochloric acid is consumed for each g of the ignited salt.

按说400多摄氏度灼烧残渣就Mg3(PO4)2。如果是Mg3(PO4)2溶解到MgCl2，我算了下，1g样品用14.8~15.4mL的1mol/L的盐酸溶解是不够的。

这个过程具体如何理解呢？请高手指点，谢谢！
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FROM 117.82.165.*

恩，自己想通了，应该是：
Mg3(PO4)2+4HCl=2MgCl2+Mg(H2PO4)2

谢谢！
【 在 c2h2c2h2 (飞飞飞扬) 的大作中提到: 】
: 不会全到氯化镁啊，
: 大部分会是磷酸二氢镁和氯化镁
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FROM 221.224.1.*