Glaubers Salt Sodium Sulfate Decahydrate Explained

The Glauber's salt is the decahydrate sodium sulphate form. It can also be called the mirabilite. The chemical formula for the Glauber’s salt is denoted by Na2SO4.10H2O. This salt is the vitreous mineral with the white or colourless appearance. This forms the evaporite from the brines comprising of the sodium sulphate. You should also note that the compound is known to form naturally along the saline springs and saline playa lakes. The name of the Glauber’s salt was given after the German-Dutch chemist and the alchemist - Johann Rudolf Glauber.

The Structure of the Glauber’s Salt

The decahydrate crystals contain the [Na(OH2)6]+ ions having octahedral molecular geometry. The octahedra shares the edges. 8 out of these 10 water molecules are further bound to the sodium, and the remaining two are hydrogen bonds, interstitial and they are bonded to the sulphate. The resulting cations are linked to sulphate anions via hydrogen bonds. The crystalline sodium sulphate decahydrate is uncommon amongst hydrated salts for having the moderate residual entropy of 6.32 J⋅K−1⋅mol−1. This indicates the ability of distributing water rapidly in comparison to most other hydrates.

The Properties of Glauber’s Salt

Physical Properties: The Glauber’s salt or the sodium sulphate the unusual soluble characteristics in the water. The solubility for this specific compound in the water goes up ten times ranging between 0 degrees celsius to 32.384 degrees celsius, and at that point it reaches 49.7g/100 ml as the maximum level. At this point, the curve of solubility changes into slope and solubility becomes considerably independent of the temperature. 

Chemical Properties: Typically, the sodium sulphate is the electrostatically bonded ionic sulphate. The existence of the free sulphate ions in the solution is represented by easy formation of insoluble sulphates when the solutions are treated with Pb2+ Ba2+ salts and the chemical equation is as follows: Na2SO4 + BaCl2 → NaCl + BaSO4. The Glauber’s salt tends to be unreactive towards most of the oxidising or reducing agents. It gets converted to sodium sulphide at higher temperatures with the help of carbothermal reduction. 

The Uses of Glauber’s Salt

Glauber's salt is widely used as the laxative in numerous medications. This compound is also effective in the removal of excessive drugs, such as paracetamol, from the body when it is used in overdose. This compound is also useful for storing low-grade solar heat when it is transforming from the solid phase to the liquid phase. The chemical industry also uses Glauber's salt for producing several important chemicals from a commercial point of view.

Chemical Properties

Typically, sodium sulphate is an electrostatically bonded ionic sulphate. The free sulphate ions’ existence in the solution is represented by the easy formation of the insoluble sulphates when these solutions are treated either with Pb2 + Ba2 + salts, where the chemical equation is listed below.

Na2SO4 + BaCl2 → 2 NaCl + BaSO4

Glauber's salt is unreactive toward most reducing or oxidising agents. It is converted to the sodium sulphide at higher temperatures using the carbothermal reduction (heating with charcoal, and more, at high temperature) as represented with the chemical equation below.

Na2SO4 + 2C → Na2S + 2CO2

This chemical reaction was employed in the process of Leblanc, which is a defunct industrial route to the sodium carbonate.

Glauber's salt reacts with the sulfuric acid to produce acid salt sodium bisulfate, where the chemical equation is represented below.

Na2SO4 + H2SO4 ⇌ 2 NaHSO4

Glauber's salt shows a moderate tendency to form double salts. The only alums that are produced with common trivalent metals are NaCr(SO4)2 and NaAl(SO4)2 (unstable above 39℃), in contrast to ammonium sulphate and potassium sulphate, which form various stable alums. Double salts with a few other alkali metal sulphates are known, including the Na2SO4·3K2SO4 that occurs naturally similar to mineral aphthitalite. The formation of glaserite via sodium sulphate reaction with potassium chloride has been used as a method for the production of potassium sulphate, which is a fertiliser. Another double salt is NaF·Na2SO4.

Production of Glauber's Salt

The world production of Glauber's salt or sodium sulphate, almost exclusively in the decahydrate, amounts to nearly 5.5 to 6 million tonnes (Mt/a) annually. In 1985, the production was 4.5 Mt/a, which is half from natural sources and a half from chemical production. Whereas, after 2000, at a stable level until 2006, the natural production had tremendously increased to 4 Mt/a, and at the same time chemical production has decreased to 1.5 to 2 Mt/a, with 5.5 to 6 Mt/a as a total. For all the applications, chemically produced and naturally produced sodium sulphate are practically interchangeable.