一种准确测定热轧钢板酸洗模拟液中盐酸浓度的方法

A Method for Accurate Determination of the Concentration of Hydrochloric Acid from Simulated Picking Solutions of Hot Rolled Steel Strip

用EDTA-Ca、KSCN以及NH4SCN作为有Fe2+存在的热轧钢板酸洗模拟溶液中Fe2+掩蔽剂,用NaOH滴定法测定溶液中盐酸的浓度,并记录溶液pH值随NaOH溶液消耗的体积变化,选择相应的曲线段的数学拐点作为滴定终点。结果发现这些掩蔽剂的加入都可使测定误差降低,测量误差从18.75%(没有掩蔽剂)分别降低为-7.9%,3.1%和0.2%,很显然,NH4SCN掩蔽效果很好。NH4SCN作为亚铁离子掩蔽剂,用在Fe2+存在的酸性溶液中盐酸浓度测定,这之前未见报导。该方法具有操作简单、准确的特点。

EDTA-Ca, KSCN and NH4 SCN were tested as the masking agents of the Fe2＋ of the simulated pickling solutions in the presence ofFe2＋, A volumetric method using NaOH as titration agent was studied for the determination of HC1 concentration from the pickling solutions in this work. The variation of solution pH with the volume of NaOH solution consumed was re- corded. The mathematical inflection point of the curve section corresponding to a pH jump was selected as the endpoint of titration. It was found that the relative measurement errors were re- duced from 18.75%（No masking agent）to-7.9 %, 3. 1 % and 0. 2 % for EDTA-Ca, KSCN and NH4SCN, respectively. Thus NHgSCN was the best masking agent of the ferrous ions.It has never reported before that NH4SCN is used as a masking agent of concentration of hydrochloric acid from acidic solutions in the simple and accurate. of ferrous ions for determination presence of Fe2＋. This method is