Question

A turbidimeter using blue cobalt plate is :

• A. Tube turbidimeter
• B. Plate turbidimeter
• C. Baylis turbidimeter
• D. Jackson turbidimeter

Answer 1

The correct option is D Jackson turbidimeter

Measurement of turbidity is done using the following :
(a) Turbidity rod
(b) Jackson turbidimeter
(c) Baylis turbidimeter
(d) Nephelometer
Baylis Turbidimeter

• It consists of a closed galvanized iron box, on one side of which, two glass tube can be held vertically side by side.
• On the other side, in front of the tubes, a $250$ watts electric bulb is located with a reflector, so as to throw light on the tube.
• The glass tube are supported at bottom by a white opal glass plate and surrounded by blue cobalt plates.
• One of the two glass tube is filled with water sample and other is filled with standard water sample of known turbidity.
• Match test sample with different standard water sample till colour of both the tubes is same.

Jackson's Turbidimeter

• In this method, the level of water kept in jar is increased till the image of flame kept at bottom of jar ceases to be seen.
• It is used when turbidity is greater than $25ppm$.
• It is a laboratory method.
• This method is not used for drinking water.

Nephelometer

• A technique to measure level of light scattered by the particles at right angles to the incident light beam.
• The unit of expression is NTU (Nephelometer turbidity unit).

Hence, $NTU$ is based on scattering principle.

• The turbidity unit is also sometimes known as $FTU$ (formazine turbidity unit).

Turbidity Rod

• Rod with platinum needle is inserted inside water and the depth at which platinum needle just becomes invisible gives turbidity in ${}^{\prime }pp{m}^{\prime }$.
• As depth of insertion increases, reading will decrease.
• It is a field method.