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Sodium metaborate

physical science Maturity 11-13 Next article →

Sodium metaborate is a special chemical compound. It is made of sodium, boron, and oxygen.

This substance appears as colorless crystalline solids. It can also be found in many different hydrates. A hydrate is a solid that holds water inside its structure. The anhydrous form, which has no water, is hygroscopic. This means it likes to pull water from the air. This compound is very important for making many different things.

How this substance works depends on its temperature. Different versions of the crystal form at different heat levels. A tetrahydrate forms between -6 and 53.6 degrees Celsius. A dihydrate forms between 53.6 and 105 degrees Celsius. A hemihydrate forms from 105 degrees up to the boiling point.

When you dissolve it in water, the anion combines with two water molecules. This creates a new thing called a tetrahydroxyborate anion. The way the atoms are arranged changes as the heat changes.

Scientists have studied how these atoms sit together. In the anhydrous form, the atoms form a hexagonal crystal system. This shape contains six-membered rings. These rings are made of alternating boron and oxygen atoms.

One extra oxygen atom attaches to each boron atom. All nine of these atoms lie on a flat plane. In the dihydrate form, the crystals use a triclinic system. The density of the anhydrous salt is 2.348 grams per cubic centimeter.

People can make sodium metaborate in a few ways. One way is to melt sodium carbonate and boron oxide together. You can also melt borax with sodium hydroxide at 700 degrees Celsius.

Another way involves heating tetraborate to 270 degrees Celsius in a vacuum. The boiling point is 1434 degrees Celsius. This is lower than the boiling point of boron oxide. Borax has a boiling point of 1575 degrees Celsius. Boron oxide has a boiling point of 1860 degrees Celsius.

This compound helps us in our daily lives. It is used to manufacture borosilicate glasses. These glasses are very strong against uneven or fast heating. This is because they have a small coefficient of thermal expansion.

Sodium metaborate is also used in the composition of herbicides. These are used to manage weeds. Finally, it can raise the pH of fluids used for oil extraction. This helps move fluids during the process of getting oil from the ground.

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