Baumé Hydrometer

Written by Rahul Verma | Updated: September 10, 2025

Bitumen sample being tested for penetration and viscosity in materials testing laboratory

Baumé Hydrometer

The device essentially consists of a long, weighted glass bulb with a sealed neck immersed in the liquid being measured. The flotation depth indicates the liquid’s density and the neck can be calibrated to read density, specific gravity, or another related property.

In actual use, the floating glass bulb is typically placed inside a cylindrical glass tube with a rubber ball at the top end to draw liquid into the tube. The bulb’s immersion depth is adjusted to read the required characteristic. A storage-battery hydrometer is a common tool used to measure the specific gravity of battery liquid and assess the battery’s state of health. The radiator hydrometer, another tool, calibrates a float using the radiator solution’s freezing point. Others may be calibrated using the alcohol solution’s “proof” or the amount of sugar in a sugar solution as a measure of concentration.

Baume hydrometers are instruments used to measure the density of liquids. They are commonly used in the chemical, pharmaceutical, and food industries. Here are some specific use cases for Baume hydrometers:

In the chemical industry, Baume hydrometers are used to measure the density of acids, alkalies, and other chemical solutions.
In the pharmaceutical industry, Baume hydrometers are used to measure the specific gravity of various solutions, including liquid medications, creams, and ointments.
In the food industry, Baume hydrometers are used to measure the sugar content of liquids such as fruit juices and syrups.
Baume hydrometers can also be used in the brewing industry to measure the sugar content of wort, which is a key step in the beer-making process.
In the automotive industry, Baume hydrometers are used to measure the density of battery acid, which is important for maintaining the health and performance of car batteries.

Video 01: Hydrometer science