lactometer

A lactometer (or galactometer) is a hydrometer used to test milk.

Milk certified as pure with a lactometer was called degree milk owing to a mistaken association with the thermometer.

Specialized hydrometers are frequently named for their use: a lactometer, for example, is a hydrometer designed especially for use with dairy products.

He obtained aid from the Board of Health in suppressing the gases emanating from the gas houses, and opposed its action in adopting the "lactometer with the senses" as the sole means of testing the purity of milk.