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各种光度计上用的比色皿,不论石英质的或玻璃质的,都要求无色透明,使它在单色光通过时光密度为常数,以保证比色时读出的光密度值能准确地反映溶液浓度的变化。在日常分析中,由于使用比色皿的次数多或因使用后未洗净,有色物质粘附于皿的四壁,久而久之,本来不甚明显的有色膜,由于积累和氧化(如双硫腙被氧化为棕色)使比色皿带上颜色。这种颜色,用一般洗涤方法(如用棉花-洗衣粉溶液揩拭或用有机溶剂洗)不易除去;用强酸性氧化剂(如王水、浓硝酸、重铬酸钾-
Cuvettes used on a variety of photometers, regardless of quartz or vitreous, require colorless and transparent so that it passes through the monochromatic light when the optical density is constant, in order to ensure that the value of optical density reading colorimetric Accurately reflect changes in solution concentration. In routine analysis, due to the use of more than the number of cuvettes or unwashed after use, the color material adheres to the four walls of the cumen. As time passes, the color film, which is not quite obvious at the moment, accumulates and oxidizes (such as dithizone Is oxidized to brown) to bring the cuvette to color. This color, with the general method of washing (such as using cotton - washing powder solution or wipe with organic solvents) is not easy to remove; with a strong acid oxidant (such as aqua regia, concentrated nitric acid, potassium dichromate -