November 1, 2021

The hydrometer is an instrument used to make measurements and determine the density of liquids. Also called an aerometer, this instrument has been used since 300 BC and its invention is attributed to Hypatia of Alexandria, a mathematician and philosopher. It determines density based on Archimedes’ principle of buoyancy.

What is the Densimeter?

The hydrometer measures the relative density of liquids . The density in the relationship between mass and volume of a substance, expressed as a magnitude. The relative density is specifically the result of the comparison of a determined density with a reference one. The reference is commonly that of water (under specific conditions of temperature and pressure).

Since density is the product of a relationship between mass and volume, there are ways to estimate it by obtaining these properties. However, the hydrometer does not require this to determine it. The principle of Archimedes buoyancy indicates each object arranged in a substance undergoes a vertical thrust force which is equal to the density of the substance.

The hydrometer then works as a float, this is a hollow, cylindrical glass tube with a mercury bulb that stays inside the substance and allows it to float upright. The other end of the cylinder indicates the density of the substance and is graduated for this.

What is the Densimeter for?

Each substance has different densities depending on its composition. The hydrometer allows you to measure its density, or what is the same, to determine if the liquid is heavy or light. The unit of density is kg / m 3  because this is the ratio between the mass and the volume of a substance or body.

However, as the density meter uses the density of water as a guide or comparison and this is 1 gr./cm 3 , so the measurement of gram per cubic centimeter is used precisely since most substances have a similar density to that of water.

Determining the density of substances also establishes their buoyancy. A substance floats on one if it has a lower density, and the same is any body; for this reason there are objects that sink and others that float, depending on the substance. With the hydrometer these qualities can be determined and compared between substances.

Using the Densimeter

Density meters are used in many areas and it is that measuring the density of substances allows even determining their purity . Since an unsuitable density for “X” substance indicates that there are irregularities in its composition; either by the elements or the concentration of these in the substance.

One of the sectors that most benefits from the use of the hydrometer is commercial or industrial. Products such as milk, alcohol, various beverages or even sulfuric acid must pass density tests to establish what they are suitable for going to the public, as they depend to a large extent on this characteristic.

The hydrometer is then used as a tester, usually with substances to which a standard density has been established and which must comply with it, whatever the area. Likewise, it is clearly used in the field of physics and chemistry for its investigations with substances and analysis of compounds.

This is a simple to use instrument that does not require a study of the instrument to use it properly. Simply place the instrument on the substance and let it rest until it floats upright. The measurement is taken depending on how much the substance was immersed and it is just sampled by the graduated tip. As you mark the point where it submerges, that is the density.

Types of Densimeters

The different types of density meters are designed for certain substances, which require different measurement scales. Either because they are of a much higher or lower density than that of water or because of the type of composition of the substance. The main types of density meters are the following:

  •  Lactometer

Of specific use for milk, this thanks to the elements that make it up, such as water, albumin, sugar, etc.

  • Saccharometer

Measure the sucrose levels of the molasses; substance that due to its density cannot be processed to produce sugar.

  • Salinometer

Measure salts in semi-solid foods.

  • Breathalyser

This specifically measures the volume of ethanol to determine the alcoholic strength. Named by its creator Gay-Lussac who also gives the measurement system its name, indicated as GL.

For each density meter, particular measurement measurements must be taken, although all basically have the same principle of use. For example, in the breathalyzer the temperature is a determining factor that can modify the result. It is also worth mentioning that there are currently digital density meters as a more advanced option than what has been used until now.

Characteristics of the Densimeter

As a simple instrument the density meter does not have a wide range of characteristics but it is vital to know them in order to recognize the instrument and apply it correctly. For this reason I will proceed to leave you the three essential characteristics of the hydrometer:

  • Material : mainly made of glass
  • Size : varies but is small, lightweight, and transportable
  • Shape : cylindrical, in addition to being hollow, its oval end stands out

You must bear in mind that it will suffer slight variations depending on the type of hydrometer and that even the digital ones are completely different, coming to look like boxes or weights of those used in the market. However, the hydrometer as such has a fairly standard appearance.

Importance of the Densimeter

Knowing the density of the substances that we consume and use in various areas is vital to detect their proper preparation . It is true that they may have other types of problems that do not affect their density, but this is one of the first filters that must pass, because it is really easy for it to be affected by changes in the substance.

Likewise, for specific types of density meters such as the breathalyzer, its importance is even better defined in ensuring the safety of consumers and those who interact with them. In the fields of physics and chemistry it is highly used, as well as in the preparation of substances in general.

These instruments are part of your day to day even if you have never been in the need to use no and knowing them is really important.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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