The key difference between sodium sulphate and sodium sulphite is that the sodium sulphate has a sulphate anion consisting of one sulfur atom and four oxygen atoms whereas the sodium sulphite has a sulphite anion consisting of one sulfur atom and three oxygen atoms. Moreover, sodium sulphate is hygroscopic while sodium sulphite is less soluble in water comparatively.
Both sodium sulphate and sodium sulphite are inorganic chemical compounds. When considering the chemical formulas of these two compounds, they differ from each other from the number of oxygen atoms that they have.
What is Sodium Sulphate?
Sodium sulphate is an inorganic compound having the chemical formula Na2SO4. It has several hydrated forms as well. The most common hydrate is decahydrate form. All anhydrous and hydrated forms are white crystalline solids. Moreover, this compound is hygroscopic.
The molar mass of this compound is 142.04 g/mol (anhydrous form). It is odorless, and the melting point and boiling points are 884 °C and 1,429 °C. Therefore, it may have either orthorhombic or hexagonal crystal structures. More importantly, this compound is very stable. It is thus unreactive towards many oxidizing and reducing agents. However, at high temperatures, it converts into sodium sulphide via carbothermal reduction.
Apart from that, this compound is a neutral salt. Therefore, the aqueous solution of this compound has a pH of 7. Also, this compound can react with sulfuric acid giving the acid salt sodium bisulfate. When considering the applications of this compound, the decahydrate form is useful in manufacturing detergents and many other commodities. Moreover, it is important in Kraft process and paper pulping.
What is Sodium Sulphite?
Sodium sulphite is an inorganic compound having the chemical formula Na2SO3. It is a soluble salt of sulfurous acid. It forms as a product of sulfur dioxide scrubbing in fuel-gas desulfurization process. Moreover, it is useful as a preservative in preserving dried fruits (to preserve the color).
The molar mass is 126.04 g/mol. The melting point is 33.4 °C, and at higher temperatures, it decomposes; thus, there is no boiling point for this. Furthermore, this compound can form a bisulfite adduct via reaction with aldehydes, ketones, which form sulfonic acid. It is useful in purifying aldehydes or ketones. In addition to that, this compound is not much stable; it may get decomposed even by weak acids. And, this decomposition produces sulfur dioxide gas. The normal pH of a saturated aqueous solution is 9. However, when it is exposed to air, eventually converts into sodium sulphate.
What is the Difference Between Sodium Sulphate and Sodium Sulphite?
The key difference between sodium sulphate and sodium sulphite is their molecular structure. Also, there are other distinguishable differences between sodium sulphate and sodium sulphite in their chemical and physical properties such as stability, solubility, boiling and melting points, etc.
The below infographic presents more details on the difference between sodium sulphate and sodium sulphite in tabular form.
Summary – Sodium Sulphate vs Sodium Sulphite
Sodium sulphate and sodium sulphite are inorganic salts of sodium. The key difference between sodium sulphate and sodium sulphite is that the sodium sulphate has a sulphate anion, which has one sulfur atom and four oxygen atoms whereas sodium sulphite has a sulphite anion, which has one sulfur atom and three oxygen atoms.
1. “Sodium Sulfate Anhydrous.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here
2.“Sodium Sulfite.” Wikipedia, Wikimedia Foundation, 27 July 2018. Available here