水生态学杂志2016，Vol.37Issue(1)：9-15,7.DOI:10.15928/j.1674-3075.2016.01.002
pH、指示剂种类及用量对络合法滴定碳酸钙的影响
Effects of pH and Indicator Type and Concentration on Calcium Determination by Complexometry
摘要
Abstract
Calcium carbonate is an important substance in chemistry and medicine, the primary constituent of mol-lusk shells and it plays an important role as an ecological carbon sink.The content of calcium carbonate is deter-mined primarily by complexometric titration of calcium ions ( Ca2 +) with disodium ethylenediaminetetraacetic acid ( Na2 EDTA) after acid dissolution of calcium carbonate.The method is simple and fast, but the titration endpoint is influenced by pH and choice of indicator.To investigate the effects of indicator, indicator concentration and pH on the complexometric determination of calcium carbonate, three experiments were carried out.( 1 ) Regression curves using eight indicators were obtained for EDTA consumption during the titration of calcium, using the same sample volume and different calcium concentrations.(2) The variation in endpoint color change with pH was stud-ied for ten indicators at five pH values (8, 9, 10, 11, 12, 12.75).(3) EDTA consumption was determined in the titration of calcium using three dosage levels of fourteen indicators.Results show that the standard curves for all eight indicators well express the relation between consumption of EDTA and content of calcium carbonate, with R2 of all fitted functions >0.999.During the titration process, the indicator color varied with pH and EDTA consump-tion varied with the type and dosage of indicator, thus affecting the calcium determination.For complexometric de-termination of calcium carbonate, the optimal mass concentration of calcium carbonate is <0.5% and murexide-naphthol green B and Eriochrome Black T are the recommended indicators, and the optimal dosage is 14.34 mL.关键词
碳酸钙/络合滴定法/指示剂/pHKey words
calcium carbonate/complexometry titration/indicator/pH分类
海洋科学引用本文复制引用
徐海龙,许莉莉,王芮,谷德贤,白东清..pH、指示剂种类及用量对络合法滴定碳酸钙的影响[J].水生态学杂志,2016,37(1):9-15,7.基金项目
农业部北方海水增养殖重点实验室基金资助（2014MSENCKF09）；天津市津南区科技计划项目（2014NY009）。 （）
