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钍-二甲酚橙络合物在pH=2.5～3.5的缓冲溶液中呈红色,当有氟离子存在时则发生减色作用,其间存在着定量的关系。作者曾建议应用钍-二甲酚橙法来作氟化物的比色测定。实验证明:这是一个可行的分析方法,且有一定的优点。原文提出的试样处理手续,系先在试液中加入硝酸铅以除去一部分的阴离子,如S~=、Cl~-、SO_4~=等,然后将滤液通过强酸性阳离子交换树脂,以除去金属离子。但因氯化铅和硫酸铅在水溶液中的溶解度并非太小,即使依照计算量加硝酸铅至80～100%,也不能将水溶液中大部分的Cl~-和SO_4~=离子除去,反而将较大量的铅离子引进试液中
Thorium - xylenol orange complex in pH = 2.5 ~ 3.5 buffer solution was red, when there is the presence of fluoride ion discoloration occurs, there is a quantitative relationship between. The authors have suggested the use of thorium-xylenol orange method for fluoride colorimetric determination. Experiments show that: This is a viable analytical method, and has certain advantages. Original sample processing procedures, the Department of the first test solution was added lead nitrate to remove some of the anions, such as S ~ =, Cl ~ -, SO_4 ~ = and so on, and then the filtrate through the strong acid cation exchange resin to remove the metal ion. However, due to the solubility of lead chloride and lead sulfate in aqueous solution is not too small, even in accordance with the calculated amount of lead nitrate to 80 ~ 100%, the aqueous solution can not be the majority of Cl ~ - and SO_4 ~ = ions removed A larger amount of lead ions into the test solution