Lactometer

Lactometer is a cylindrical vessel made by blowing a glass tube. One side of glass tube looks like a bulb filled with mercury and another side is a thin tube with scale. 

For milk testing, lactometer is dipped in milk which we are testing. In lactometer, the point up to which it sinks in the pure milk is marked after that put in water and marked at the point up to which it sinks in water. It sinks less in milk than water because as we know milk is denser than water. 

In the lactometer there are two portions i.e. ‘M ‘and ‘W’ which is divided into three parts and marked as 3, 2 and 1. That indicates the level of purity in milk.