Question

What is a lactometer? Explain its principle and work.

Answer 1

One form of hydrometer is a lactometer, an instrument used to check the purity of milk. The lactometer works on the principle of gravity of milk. The lactometer consists of a long graduated test tube with a cylindrical bulb with the graduation ranging from 15 at the top to 45 at the bottom. The test tube is filled with air. This air chamber causes the instrument to float. The spherical bulb is filled with mercury to cause the lactometer to sink up to the proper level and to float in an upright position in the milk.

Inside the lactometer, there may be a thermometer extending from the bulb up into the upper part of the test tube where the scale is located. The correct lactometer reading is obtained only at a temperature of 60°C. A lactometer measures the cream content of milk.

The more the cream, the lower the lactometer floats in the milk. The average reading of normal milk is 32. The lactometers are used highly in milk processing units and at dairies.