To determine the colour of given sample of water by direct observation.
Principle The standard unit of colour is the colour produced by dissolving 1mg of platinum cobalt in 1 litre distilled water.
Different standard colour intensities of solutions are prepared by dissolving known amounts of platinum cobalt with
distilled water and the colour of sample is compared with the standard colour solutions.
- Nessler tubes,
- Volumetric flask,
- Pipettes etc.
- Take 0.1mg of platinum cobalt and dissolve in 100 mL distilled water.
- Take 1 mL, 2 mL, 3 mL etc. of this solution and dilute to 50 mL, such that we get solutions of
concentrations 1/50, 2/50, 3/50, (n/50) mg/L etc. These are the comparator solutions.
- Take the sample and the comparator solutions in the Nessler tubes and compare the colour.
- Note down the dilution of the comparator solution having the same colour as the sample.
- If corresponding colours are not developed, the sample may be diluted to get the corresponding colour.
Observation and Calculation