六价铬测定(英文版)

ExperimentⅦthe determination of Cr (VI) in water The purpose and requirements of the experiment

1.Learn the method of determiningCr (VI) and the usage of spectrophotometer.

2.Know the GB of water about chromium and the difference toxicity between Cr

(VI) and Cr (Ⅲ).

3.After finishing experiment we must wash our hands, or else we will poison

when we eating.

4.Do not eat and drink anything in lab, and don’t touch mouth and eyes,

becausemany drugs are toxic.

Experimental program

1.Experimental instruments and drugs

More than 12 clear 50ml colorimetric tubes and 1 clear

Spectrophotometer

Beaker, pipette, filter paper and funnel

(1+1) sulfuric acid (H2SO4)

(1+1)phosphoric acid (H3PO4)

Chromogenic reagent (DPC)

Zinc hydroxide coprecipitator

More than 50ml industrial wastewater

2.Experimental steps

The preparation of industrial wastewater:take 50mL industrial wastewater into colorimetric tubes and dilute to 100mL standard line, shake up.After put Zinc hydroxide coprecipitator into the industrial wastewater and shake up a minute, take 15mL wastewater to make filter paper to be moist, then dry-filter wastewater and divide different concentration into 5 clear 50ml colorimetric tubes (5ml, 5ml, 10ml, 10ml, 20ml) and dilute to 50mL standard line.

The preparation of different concentration chromium standard solution: take 10ml chromium standard solution (10mg/L) into 100ml colorimetric tubes and dilute to 100ml standard line, shake up. Then respectively take 0ml, 1ml, 2ml, 4ml, 6ml, 8ml, 10ml, water into 7 clear 50ml colorimetric tubes from tube by pipette, and respectively dilute to 50ml standard line, shake up.

Color processing: add 0.5ml (1+1) H2SO4 and 0.5ml (1+1) H3PO4 into eachtubes (7 standard tubes and 5 wastewater tubes), shake up them. Lastly decant 2ml DPC to each tubes, shake up them, then lay aside them for 5 minutes.

Determining Absand draw up the graph: set the wavelength ofSpectrophotometer

in 540nm. The first determine 4 dishes difference and mark which tube is put into which dish to determine, then determine each tubes and writ every data down table. Let the Abs be the ordinate and the concentration of Cr (VI) be the abscissa and draw up the graph. Through the graph, calculate the concentration of Cr (VI) in industrial wastewater.

Experimental result and data handling

coordinate system.

Fig. 1 Abs-the concentration of Cr (VI) in 50ml colorimetric tube According to fig. 1 and the following formula we can calculate the concentration of Cr (VI) in wastewater’s tubes.

Notes: y refers to theAbs of Cr (VI) in wastewater

c refers to The concentration of Cr (VI) in tube(mg/L)