happyjyl
第1楼2012/05/11
ferric ammonium sulfate是硫酸铁铵,VS是指滴定液(volumetric solutions)。
N在USP里指normal solutions,你说的mol/L在USP里指molar solutions。二者的定义见下:
http://www.pharmacopeia.cn/v29240/usp29nf24s0_volumetric-solutions-1345-1360.html
对有些溶液来说1N即1mol/L,对硫酸铁铵溶液来说是否如此我就不知道了。我化学不好,你问问别人吧。
USP里有专门的章节介绍如何配制滴定液,详见VOLUME 1的Reagents, Indicators, and Solutions里Volumetric Solutions。我手头没有USP,哪位网友有的话上传一下吧。
深海的海豚
第2楼2012/05/11
谢谢happy~!我再看一下美国药典。
影子
第4楼2012/05/14
药典上只有0.1N的,0.05N的在这个基础上称样量减半配制再标定就可以了:
Ferric Ammonium Sulfate, Tenth-Normal (0.1 N)
FeNH4(SO4)2·12H2O, 482.19
48.22 g in 1000 mL
Dissolve 50 g of ferric ammonium sulfate in a mixture of 300 mL of water and 6 mL of sulfuric acid, dilute with water to 1000 mL, and mix. Standardize the solution as follows.
Accurately measure about 40 mL of the solution into a glass-stoppered flask, add 5 mL of hydrochloric acid, mix, and add a solution of 3 g of potassium iodide in 10 mL of water. Ins-ert the stopper, allow to stand for 10 minutes, then titrate the liberated iodine with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached. Correct for a blank run on the same quantities of the same reagents.
Store in tight containers, pro-tected from light.
深海的海豚
第6楼2012/05/14
谢谢影子,在你的帮助下我已经找到原文,没有问题了!