Experiment on the determination of water chromaticity

Summary

Clean water should be colorless at shallow depths and light blue-green at deeper depths. The presence of humus, mud, plankton, metal ions such as iron and manganese in natural water can color the water. Water color (Clour) unit is degree, that is, in each liter of water containing 2mg cobalt chloride hexahydrate (equivalent to 0.5mg cobalt) and 1mg platinum when the color produced for 1 degree. Determination of cleaner natural water and drinking water chromaticity, commonly used platinum and cobalt standard colorimetric method, the results expressed in degrees, the surface water contaminated by industrial wastewater and industrial wastewater, can be used to describe the color type and depth of the degree of text, and to dilute the multiplier method to determine.

Operation method

Platinum-cobalt standard visual colorimetric method

Materials and Instruments

Wastewater
Cobalt sulfate Potassium chloroplatinate Potassium dichromate Water Sulfuric acid
Plugged cuvettes Test tube racks

Move

I. Reagents and drugs

1. Drugs
(1) Cobalt sulfate ( _CoSO4-7H2O )
(2) Potassium chloroplatinate ( _K2PtCl6 ), which may be replaced by potassium dichromate.
2. Reagents
Platinum cobalt standard solution: weigh 0.0437 g of potassium dichromate and 1.000 g of cobalt sulfate ( _CoSO4-7H2O ), dissolve them in a small amount of water, add 0.5 mL of sulfuric acid, and dilute with water to 500 mL, and the chromaticity of this solution is 500 degrees. It should not be stored for a long time.
II. Experimental steps
1. Preparation of standardized Israel

Add 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0 mL of platinum-cobalt standard solution to a 50 mL colorimetric tube, dilute with water to the mark and mix well. The chromaticity of each tube is 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70 degrees. Keep tightly plugged.
2. Measurement of water samples
(1) Aspirate 50.0 mL of clarified water sample into a colorimetric tube. If the water sample is more colorful, it can be taken sparingly and diluted to 50.0 mL with water.
(2) Visual comparison of the water sample with the standard color scale. Observation, the colorimetric tube can be placed on white paper, so that the light from the bottom up through the liquid column, the eyes from the mouth of the tube vertically downward observation, note down and water samples with the same chromaticity of the standard color scale of Israel.
3. Calculation of results
Chromaticity (degrees) = A x 50/B
Style:A - diluted water samples equivalent to platinum cobalt standard Israel chromaticity ;B - volume of the water sample, mL .

Caveat

1, such as the determination of the true color of the water samples, should be placed on the clarification of the supernatant, or centrifugation to remove the suspended material measured; such as the determination of the apparent color of the water samples, to be in the water samples of large particles in the suspension of precipitation, take the supernatant measured. 2, pay attention to the representativeness of the water samples.

2. pay attention to the representativeness of the water samples, the water samples taken without twigs, branches and other floating objects.

3. Retrieve the water sample should be measured as soon as possible, otherwise it should be stored at 4 ℃ refrigerated, measured within 48 hours.

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