Determination of hexavalent chromium English versionExperimentⅦthe determination of Cr VI in waterThe purpose and requirements of the experiment1 Learn the method of determiningCr VI and the usage of

tube, and add 1ml DPC reagent and 1ml (1+1) sulfuric acid solution to each tube, shake up. Then add 0.5ml (1+1) phosphoric acid solution to each tube and shake up again. Finally, add different amount of chromium standard solution (0ml, 1ml, 2ml, 4ml, 6ml, 8ml, 10ml) to each tube respectively, shake up and let stand for 10min.

Measurement of absorbance: set the spectrophotometer wavelength to 540nm, use water as blank control, measure the absorbance of each tube, record the data.

Calculation of concentration: draw the standard curve with the absorbance value as the ordinate and the concentration of chromium standard solution as the abscissa, and calculate the concentration of Cr (VI) in the industrial wastewater according to the standard curve.

3. Precautions

(1) The concentration of the chromogenic reagent and the (1+1) sulfuric acid solution should be accurate, otherwise it will affect the accuracy of the measurement.

(2) The spectrophotometer should be calibrated before use to ensure accurate measurement.

(3) The experiment should be carried out in a well-ventilated place, and personal protective equipment such as gloves and goggles should be worn to avoid contact with toxic substances.

(4) The waste liquid and waste filter paper should be treated properly to avoid environmental pollution