Glauber's salt can be defined as the decahydrate sodium sulfate form. It can also be referred to as mirabilite. The Glauber's salt's chemical formula can be given as Na2SO4.10H2O. This Glauber's salt is a vitreous mineral with a colourless or white appearance, which forms as an evaporite from brines comprising sodium sulfate. It should also make a note that this compound is known to form naturally along saline playa lakes and around the saline springs too. Glauber's salt was named after the alchemist and German-Dutch chemist - Johann Rudolf Glauber.
It is also important to note that Glauber's salt is quite unstable in dry air. When placed in such environmental conditions, this compound is well known to undergo dehydration rapidly. When this happens, the Glauber's salt crystals are transformed into a white powder that has a chemical formula Na2SO4. This white powder is often pointed to as thenardite. Moreover, thenardite is also well known to possess the ability to absorb water and convert it into mirabilite subsequently.
Structure of Glauber’s Salt
The decahydrate crystals contain [Na(OH2)6]+ ions with octahedral molecular geometry. These octahedra share the edges. Eight of 10 water molecules are further bound to sodium, and the other two are interstitial, hydrogen bonds, and bonded to sulfate. These resultant cations are linked to the sulfate anions through the hydrogen bonds. The Na-O distances can be given about 240 pm. Also, the crystalline sodium sulfate decahydrate is unusual among the hydrated salts in having a moderate residual entropy (entropy, at absolute zero) of 6.32 J·K−1·mol−1. This indicates its ability to distribute water very rapidly compared to most hydrates.
What Are the Properties of Glauber’s Salt?
Sodium sulfate or Glauber's Salt has unusual solubility characteristics in water. The solubility of this compound in the water rises more than tenfold, ranging from 0℃ to 32.384℃, where it reaches 49.7 g/100 mL, as a maximum level. At this specific point, the solubility curve changes into the slope, and the solubility becomes substantially independent of temperature. This particular temperature of 32.384℃, corresponding to the crystal water release and the melting of hydrated salt, works as an accurate temperature with reference for the calibration of the thermometer.
Typically, sodium sulfate is an electrostatically bonded ionic sulfate. The free sulfate ions’ existence in the solution is represented by the easy formation of the insoluble sulfates 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 oxidizing agents. It is converted to the sodium sulfide 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 sulfate and potassium sulfate, which form various stable alums. Double salts with a few other alkali metal sulfates are known, including the Na2SO4·3K2SO4 that occurs naturally similar to mineral aphthitalite. The formation of glaserite via sodium sulfate reaction with potassium chloride has been used as a method for the production of potassium sulfate, which is a fertiliser. Another double salt is NaF·Na2SO4.
Production of Glauber's Salt
The world production of Glauber's salt or sodium sulfate, almost exclusively in the decahydrate, amounts form 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 sulfate are practically interchangeable.
Glauber Salt Uses
Let us look at the uses of Glauber's salt in detail.
Sodium sulfate or Glauber's salt can be widely used as a laxative in various medications. Also, this compound is especially effective in removing excess drugs (like paracetamol) in the body when used in overdose.
Because this compound produces a relatively high heat storage capacity, it is extremely useful to store low-grade solar heat (particularly in space heating applications) when it is changing from solid phase to liquid phase. This compound can also be used to employ during the chill mats production for laptop computers. It should also make a note that the chemical industry makes extensive use of Glauber's salt for the production of various commercially important chemicals.