Milk is a mixture of fats, proteins, electrolytes, hormones and other ingredients. It is not pure so the question does not apply.
You test it by checking the melting point
The best and trusted way is by chemical test
Density
burn it if its gold it want burn
Well, it is better to use the acid test and magnet test, because any electronic test is not 100% secure
test tungsten purity
milk represents purity
Lactometer is a device used for finding the purity of a milk sample. It works on the principle of Archimede's principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced. If the milk sample is pure, then the lactometer floats on it and if it is adulterated or impure, then the lactometer sinks.
Khoya/ Mawa is sweet evaporated milk used in many Indian dishes. These evaporated milks are readily available throughout India but many people choose to make their own at home due to purity problems with store bought versions. The purity of the milk can be tested with a lactometer, though these aren't really made for home use.
You test it by checking the melting point
The best and trusted way is by chemical test
Bisleri
monkey
how would you test for milk in a milk chocolate bar
Purity tests are used to determine the extent to which a particular substance is what is claimed. A classic purity test for gold is nitric acid; if the item being examined reacts to the acid it is not gold, or at least not pure gold.
Ephedrine can show a false positive for amphetamines on a drug test.
lacto meter is a device which is used to detect the purity of milk