Gauging colour in water
colour: Light transmitted through a filtered wastewater sample is measured to give a single figure, denoting overall colour turbidity: Gauging wastewater's light-scattering properties true/apparent: Combines colour and turbidity. True colour is measured without particulate matter; apparent colour is measured with it; true is usually much lesser.
Measuring colour in wastewater is difficult. For proper results, turbidity must be removed, for it nullifies transmission of light. Colour is measured in relation to the Hazen colour scale. This method is not so satisfactory for industrial effluents, but no standardised alternative exists. Also, the Hazen scale only indicates the colour unit or the hue of the water or effluent. It cannot indicate toxic characteristics.
Colour in a water sample is visually compared to a series of standard solutions containing known amounts of potassium chloroplatinate and added cobalt (II) chloride. One true colour unit (TCU), or platinum