Question

write the applications of lactometer and hydrometer

Answer 1

Lactometer :
It is specially designed hydrometer which is used for measuring the relative density of Milk. and hence for testing the purity of milk.
If the milk is skimmed, its density is higher , so a lactometer cannot detect the purity of milk if the milk is skimmed.
It is based on the principle of Floatation.

Hydrometer :

Hydrometer is a device used for the measurement of relative density of a liquid. It is based on the principle of Floatation.

Answer 2

Lactometer is an instrument which is used to check the purity of the milk or you can say it is used to measure the density of the milk so that it can be identified how much volume of water is mixed with the milk.
Hydrometer is used to measure the density of different type of liquids it is made up of glass and is cylindrical shape.