In actual operation, the platinum-cobalt colorimetric method is only suitable for surface water, groundwater, domestic water, etc., which cannot be less serious water quality color detection. If it is more seriously polluted surface water and industrial wastewater, this kind of water body with complex color tone, it is difficult to detect by platinum-cobalt colorimetry. What should I do? In fact, analysts can use the dilution factor method to detect the chromaticity of such water quality.
The principle of the dilution multiple method to determine the color
The dilution factor method is to dilute the tested water sample with optical pure water until the color is just invisible compared with the optical pure water by visual comparison. The dilution factor at this time is the chromaticity of the water sample. At the same time, visually observe the water sample and describe the color properties in words: the depth and transparency of the color. Use the method of combining the dilution factor value and the text description to express the color.
Reagents and equipment used for color detection
1. Optically pure water.
2. Colorimetric tube with stopper: 50mL, complete set of high type colorless.
3. Volumetric flask: 250, 1000mL.
4. Pipette: 5, 10, 25mL.
5. Measuring cylinder: 250, 500mL.
6. Wash the ear ball.
Dilution multiple method to detect the steps of color
1. Pour the test water sample into a 250mL graduated cylinder and let it stand for 15 minutes, and take the upper liquid as the test water sample for measurement.
2. Take the optically pure water and place it in a 50mL colorimetric tube with a stopper, to the 50mL mark, place the colorimetric tube with a stopper on the white surface, observe the liquid column vertically, compare the water sample with the optically pure water, and describe the water The hue and transparency of the appearance.
3. Dilute the water sample to be tested with optically pure water in multiples of 2 step by step to different multiples, shake well and place them in the colorimetric tube with stopper to the 50mL graduation line, and place the colorimetric tube with stopper on the white surface , Use the same method as above to compare with optical pure water, dilute the water sample to be tested until it is just indistinguishable from optical pure water, and record the dilution factor value at this time.
4. Take another water sample to determine its pH value.
5. Calculate the multiple value by the formula of chroma=2n.
