The color of the sample is visually compared with that of the standard platinum-cobalt colorimetric solution, and the result is expressed in Hazen (platinum-cobalt) color unit. Hazen (platinum-cobalt) color unit is the color of solution containing 1mg of platinum (in chloroplatinic acid) and 2mg of cobalt chloride hexahydrate per liter.
2 Apparatus
2.1 Type 72 spectrophotometer or similar spectrophotometer.
2.2 Nessler tube: 50mL or 100mL with scale mark at 100mm above the bottom.
2.3 Colorimetric tube rack: generally, the bottom of the colorimetric tube rack is lined with a white base plate, and a reflector can be installed at the bottom to improve the color observation effect.
Preparation method of chloroplatinic acid: dissolve 1.00g of platinum in sufficient aqua regia by heating in a boiling water bath in a glass dish or a porcelain dish; after the platinum is dissolved, evaporate the solution to dryness; add 4mL of hydrochloric acid solution and evaporate the solution to dryness; repeat the operation for more than two times and 2.10g of chloroplatinic acid can be obtained.
