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本文研究了用结晶紫萃取比色测定微量钼的方法。查明了硫氰酸钼(V)-结晶紫的三元络合物,在乙醇存在下,能用苯顺利的萃取,并可直接比色测定钼。确定了较适宜的萃取酸度为3—4当量硫酸,16％硫氰酸钠的用量为2.0毫升,0.05％结晶紫为2.5毫升。水相体积在35—55毫升,温度在15—30℃时,对萃取没有影响。苯层中的有色络合物,可稳定一小时,在波长480—680毫微米间,有两个吸收峯,一于波长555毫微米;另一在605毫微米处,其克分子消光系数在555毫微米处时为7.0×10~4,在605毫微米处时为8.2×10~4,0—9微克钼/5毫升苯,符合比尔定律。共存离子:100微克的钨(Ⅵ)、钒(Ⅴ)、铼(Ⅶ)、铌(Ⅴ)、钛(Ⅳ)、镍、钴(Ⅱ)、锌、镉、铋(Ⅲ)、铅、铊(Ⅰ)、锰(Ⅱ)、铀(Ⅵ)、钍、铝;50微克的钽(Ⅴ)和铜(Ⅱ);以及8毫克的氟、50毫克的锆均不干扰。并允许有大量的硼酸、硼氟酸、酒石酸、柠檬酸以及乙二胺四乙酸等离子存在。唯有锡(Ⅳ)、锑(Ⅲ)、草酸和多量锆、硝酸根有影响,但锡锑和多量锆的影响,可用硼氟酸掩蔽消除。因而此法可在多量锆和其他若干离子存在下,直接萃取比色测定微量钼。并较二硫酚法灵敏两倍多。
In this paper, the crystal violet extraction colorimetric determination of trace molybdenum. The ternary complex of molybdenum (V) thiocyanate and crystal violet has been identified and can be successfully extracted with benzene in the presence of ethanol and the direct colorimetric determination of molybdenum. The optimum extraction acidity was determined to be 3-4 equivalents sulfuric acid, 16% sodium thiocyanate was 2.0 ml and 0.05% crystal violet was 2.5 ml. The volume of the aqueous phase is 35-55 ml and has no effect on the extraction at 15-30 ° C. The colored complex in the benzene layer is stable for one hour and has two absorption peaks at wavelengths of 480-680 nm at a wavelength of 555 nm and the other at 605 nm has a molar extinction coefficient of It is 7.0 × 10 4 at 555 nm, 8.2 × 10 -4 and 0-9 μg mol / 5 ml benzene at 605 nm, according to Beer’s law. Coexisting ions: 100 μg of vanadium (V), rhenium (Ⅶ), niobium (Ⅴ), titanium (Ⅳ), nickel, cobalt, zinc, cadmium, bismuth, (Ⅰ), manganese (Ⅱ), uranium (Ⅵ), thorium and aluminum; 50 μg of tantalum (Ⅴ) and copper (Ⅱ); and 8 mg of fluorine and 50 mg of zirconium all did not interfere. And to allow a large number of boric acid, boric acid, tartaric acid, citric acid and ethylenediaminetetraacetic acid ions exist. Only tin (Ⅳ), antimony (Ⅲ), oxalic acid and a large amount of zirconium, nitrate impact, but tin and antimony and a large amount of zirconium, boric acid can be used to eliminate masking. Thus this method can be in the presence of a large number of zirconium and other ions, the direct extraction and colorimetric determination of trace molybdenum. And more than twice as sensitive than the dithiol method.