Method for the colorimetric analysis of methanol
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Could anyone who knows methanol colorimetry methods share them with me?
4.1 Determination of chroma 4.1.1 Method summary Visual comparison is carried out between the methanol sample and a platinum-cobalt chroma standard solution. The result is expressed in platinum-cobalt chromaticity units (the color of a solution containing 2 mg of cobalt chloride hexahydrate and 1 mg of platinum per liter). 4.1.2 Instruments and Reagents 4.1.2.1 Colorimetric tubes: graduated, with a capacity of 100 mL; made of colorless glass and equipped with glass stoppers. 4.1.2.2 Colorimetric tube holder: A standard colorimetric tube holder, with a white bottom base. The Kean is equipped with a mirror to improve the color observation effect. 4.1.2.3 Salt acid: c(HCl) = 0.1 mol/L ； c(HCl) = 6 mol/L 4.1.2.4 Preparation of colorimetric standard solutions: Accurately weigh 1.245 g of potassium chloroplatinate (K2PtCl6, analytical grade) and 1.000 g of cobalt chloride (CoCl2•6H2O, analytical grade), with precision to 0.001 g. Dissolve in an appropriate amount of water, add 200 mL of 6 mol/L hydrochloric acid, transfer to a 1000 mL volumetric flask, and dilute to the mark with water. This solution is the Colorimetric Standard No. 500. Stored in a dark place, it is valid for one year. Take 0.0, 0.4, 1.0, 1.4, 2.0, 2.4, 3.0…6.0 mL of the colorimetric standard solution No. 500 and transfer it into separate 100 mL colorimetric tubes; then dilute to the mark with 0.1 mol/L hydrochloric acid to obtain the colorimetric standard solutions No. 0, 2, 5, 7, 10, 12, 15…30. Store in a dark place; it is valid for 15 days. 4.1.3 Measurement procedure: Take the sample and pour it into a 100 mL colorimetric tube up to the mark line. Compare it with the color standard solution under daylight or fluorescent lighting, against a white background, by viewing axially in order to determine the chromaticity number of the methanol sample. 4.1.4 Allowable deviation: The difference between the results of parallel measurements shall not exceed 2 grades, and the average value shall be taken as the measurement result.