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锆(铪)的絡合滴定是从1954年开始,初期大都在pH1—6間采用直接滴定或回滴法,pH值愈高,則以回滴法为宜,可避免锆的水解。J.S.Fritz等提出以茜素花色素RC(Alizarol cyanone RC)及埃鉻菁R(Eriochrome cyanine R)在pH1.3—1.5及70—90℃进行滴定或以标准锆回滴剩余的EDTA,干扰离子很多,其中有鉄、钍、銻(Ⅲ)、錫、钛、鎢、钼、硫酸根、磷酸根、氟离子等。G.Benerjee采用对磺基苯偶氮变色酸(SPADNS)在pH2.2—2.4进行锆的滴定,离子干扰与上相若。G.W.C.Milner等則提出在pH5—6以水杨酸作指示剂用标准鉄溶液滴定煮沸后放冷的剩余的EDTA;此法适宜于滴定鈾—锆合金中的锆。及后P.B.Sweeter等与Milner等分別提出在pH4.0用光度法确定終点,以提高終点的敏銳性;后者更提出可用二苯异羟肟酸鉀(benzohyd-roxamate)作指示剂(pH2.3),干扰較少。另一回滴法是在pH2以硫脲为指示剂,用标
Zirconium (hafnium) complexation titration is from 1954 onwards, most of the initial pH in the use of direct titration or droplet between 1 to 6, the higher the pH, the drop method is appropriate, to avoid hydrolysis of zirconium. JS Fritz et al proposed titration with Alizarol cyanone RC and Eriochrome cyanine R at pHs of 1.3-1.5 and 70-90 ° C or the remaining EDTA with standard zirconium back, interference ions Many, of which there are 鉄, thorium, antimony (Ⅲ), tin, titanium, tungsten, molybdenum, sulfate, phosphate, fluoride and so on. G. Benerjee uses p-sulfophenylazo chromotropic acid (SPADNS) for titration of zirconium at pH 2.2-2.4 with similar ion interference. G.W.C.Milner et al proposed the use of salicylic acid pH5-6 as a standard indicator solution titration boil after cooling the remaining EDTA; This method is suitable for titration of uranium - zirconium zirconium alloy. Later, PBSweeter et al. And Milner et al. Respectively proposed to determine the endpoint by photometry at pH 4.0 in order to improve the endpoint sharpness. The latter also proposed to use benzohydrobixamate as an indicator (pH2). 3), less interference. Another drop method is to use thiourea at pH2 as an indicator, the standard