The hydrometer is a measuring instrument used mainly in the area of physics and chemistry , although it can also be used in areas of commerce such as oenology or the science of producing quality wine, to verify the density of alcohol or sugar . It is an instrument that helps us to find the value of the density of a product in the industry.


What is the hydrometer?

The hydrometer is a measuring instrument that helps us to determine the density of a liquid without also having to calculate the mass and volume , based on Archimedes’ principle .

  • Definition
  • Characteristics of the density meter
  • Source
  • History
  • Who invented it
  • What is it for
  • Parts of a hydrometer
  • Types
  • How a hydrometer works
  • How it differs from the areometer
  • Importance


We know as densimeter to the instrument essential in the field of physics that allows reaching us to know the relative density with the substances liquid. It is the relationship that exists between the specific weight of a body and the specific weight that has been taken as a reference .


Characteristics of the density meter

Its main characteristics are the following:

  • It is generally made of glass .
  • It has a hollow cylindrical shape with a bulb at the bottom.
  • Fundamental instrument in physics .
  • It only floats when the volume of the liquid equals the weight of the device.
  • It is based on the hydrostatic principle of Archimedes .


To date, there is no specific date of when the hydrometer originated , since there are no documents that prove the theories . Despite this, many experts and historians think the 1 of December of 1783 , an important innovator , scientist and mathematician named Jacques Charles , along with Ainé Roberts , presented the first densitometer, named hydrometer.


The history of the hydrometer is believed to have originated through Hypatia of Alexandria . Historians claim that he used Archimedes’ principle to create the instrument. During the 11th century , the device was used by Abu Rayhan al-Ciruni , who was a teacher, and was later described by Al – Khazini , an astronomer . It appears in the works of Charles in the 18th century . From this moment on, many have been invented and have undergone a series of reforms and transformations.

Who invented it

It was invented by Hypatia of Alexandria , a young Neoplatonic mathematician and philosopher, who was greatly outstanding in the area of astronomy , philosophy, and mathematics.

What is it for

Its applications are aimed at measuring the relative density of liquids, without knowing their mass and volume, using Archimedes’ hydrostatic principle as a reference . It is also used to measure the concentrations of acid and gases , in the industrial and commercial field . It is used in the field of oenology , controlling the fermentation processes of sugary liquids , indicating the moment of maceration of the wine.

Parts of a hydrometer

The parts of a hydrometer are as follows:

  • A part to suck or pear .
  • A glass cylinder or tube .
  • A weight in charge of indicating the density .


  • Lactometer or Galactometer : specifically measures milk and its quality.
  • Saccharometer or Saccharometer : measures the concentration of sugar in a liquid or molasses.
  • Salimeter or Salinometer : measures the density of salts, and helps to measure the specific gravity of seawater inside the aquarium.
  • Baumé Aerometer : measures concentrations of solutions.
  • Pycnometer : accurately measures the density of solids and liquids, based on Archimedes’ principle .
  • Urinometer : determines the density of urine and is for medical use.
  • Breathalyzer : establishes alcoholic degrees in a water-based substance.
  • Battery density meter : measures the level of charge in a battery.

How a hydrometer works

It works by gradually introducing it into the liquid so that it floats freely and vertically . The point when the surface of the liquid touches the cylinder of the hydrometer is then observed on the scale . Density meters contain a paper scale inside so that you can directly read the density. In light liquids , the gauge must sink further to accommodate the weight of the liquid than in thick liquids. In fact, you can have two separate instruments: one for liquids in General and another for liquid dense little . The hydrometer is also used in oenologyto know when the wine is macerated .

How it differs from the areometer

The main difference between the two is that although they have the same foundation , aerometers are used to measure different concentrations of substances , otherwise, the density meter is used to measure only densities .


They are important because they help determine the measures of density of any substance for the development of projects . It is important in the area of physics , commerce and industry to know the characteristics of materials. It allows checking the degree of purity of substances, and helps in improving the production of high-value liquids such as alcohol , sugar and beverages .

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