1.1 Platinum-cobalt standard colorimetry
1.1.1 Scope
This standard specifies the platinum-cobalt standardcolorimetryfor determination ofcolority of drinking water and its source water.
This method is applicable to the determination of colorityin drinking water and its source water.
With this method, the water sample shall not be diluted, the minimum detectable colority is Degree 5, and the determination range is Degree 5~50.
Prior to determination, the suspended substances in water sample shall be removed.
1.1.2 Principle
Prepare standard colour series with potassium chloroplatinate and cobalt chloride, which have the similar colour tone as natural water, and use standard colour series for the visual colorimetric determination of water sample. It is specified that the colour of 1mg/L platinum [existing in the form of (PtCl6)2-] is a colority unit and is referred to as 1 degree. Even slight turbidity can disturb the determination, thus turbid water sample needs to be clear via centrifugation prior to determination.
1.1.3Reagents
Platinum-cobalt standard solution: weigh 1.246g of potassium chloroplatinate (K2PtCl6) and 1.000g of cobalt chloride (CoCl2?6H2O), dissolve them in 100mL of pure water, add 100mL of hydrochloric acid (ρ20=1.19g/mL) into the solution, and dilute the solution with pure water to 1,000mL. The colority of this standard solution is Degree 500.
1.1.4 Instruments
1.1.4.1A complete set of high-type colorless colorimetric tubes with stoppers, 50mL.
1.1.4.2Centrifuger.
1.1.5Analytical procedures
1.1.5.1Take 50mL of transparent water sample into a colorimetric tube. If the colority of water sample is overhigh, take a little water sample and dilute it with pure water, and then perform colour comparison, and multiply the result with the dilution times.
1.1.5.2Take another 11 colorimetric tubes, respectively add 0mL, 0.50mL, 1.00mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL, 3.50mL, 4.00mL, 4.50mL and 5.00mL of platinum-cobalt standard solution into each tube, dilute with pure water to the scale, and shake up, thus these solutions are standard colour series with colority of Degree 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 respectively and can be preserved for long-term use.
1.1.5.3Compare the water sample and platinum-cobalt standard colour series. If the colourtone of water sample is inconsistent with that of standard colour series, it is heterochrosis and may be described textually.
GB/T 5750.4-2006 The following standards are cited：
GB/T 5750.4-2006 Cited by the following standards：
