In these days of adulteration milk is one of the main sufferers in terms of purity because it is often mixed with other substances that make it impure. But we can find out about the purity of milk. How do we do that?
The instrument used to assess the purity of milk is called a lactometer. It is a cylindrical vessel made by blowing a glass tube. One end of the glass tube is blown in the from of a bulb and filled with mercury. The other end is blown in the from of a thin tube and sealed. For calibration it is dipped in pure milk. The point up to which it sinks in the pure milk is marked after that it is put in water and is marked at the point up to which it sinks in water. It sinks less in milk than in water because milk is denser than water. The portion between ‘M’ and ‘W’ is divided into there parts and marked as 3, 2 and 1 to indicate the level of purity.
Whenever we want to test the purity of milk, the instrument is put in milk. If it sinks up to the mark M the milk is pure. If the milk is not pure but mixed with water, it would sinks to a mark higher than M undersea ships can be directed? The main device used to detect and locate objects like submarines and torpedoes under the seawater is called sonar the word sonar is an acronym for sound navigation and ranging. This instrument is particularly useful in sea warfare. However in peacetime also it is used in shops and submarines. It can locate objects at distance ranging from 100 meters up to 10 kilometers.
When the instrument stands at the mark 3, the milks 75% pure. At the mark 2, the purity is only 50%. Mark 1 indicates a purity of 25% only.
Even though lactometer is generally used to measure the purity of milk, it is nor a very relievable instrument. It has been observer that in the case of skimmed milk the lactometer fails to give the correct assessment of the purity if the density of the skimmed milk is made equal to that of the pure milk adding water in an appropriate proportion.