Sodium Bisulfate - NaHSO₄

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What is Sodium Bisulfate?

Sodium Bisulfate, with the molecular formula NaHSO4, is the sodium salt of the bisulfate anion. It is an acid kind of salt which is formed by partial neutralisation of sulfuric acid by an equivalent of sodium base. It is typically in the form of either sodium hydroxide (lye) or sodium chloride. Sodium bisulfate is produced as a median in the Mannheim process. Mannheim is an industrial process involving the reaction of sodium chloride and sulfuric acid: NaCl + H2SO4 → HCl + NaHSO4. It is highly toxic to certain echinoderms but impartially harmless to most other life forms; so it is used in controlling outbreaks of crown-of-thorns starfish.

Properties of Sodium Bisulfate NaHSO4

There are two different properties of sodium bisulphate NaHSO4 :

Physical Properties of Sodium Bisulfate NaHSO4

Sodium bisulfate NaHSO4 is commonly available in both anhydrous (dry) and monohydrate (NaHSO4.H2O) forms. Anhydrous NaHSO4 is a shapeless and hygroscopic white powder, having a density of 2.74 g/mL and the melting point of 315 °C. The monohydrate is a white sandy solid having a density of 1.8 g/mL and a melting point of 59 °C. It is considered as a dry acid which is suitable for safe shipping and storage as well.

Chemical Properties of Sodium Bisulfate NaHSO4

Sodium bisulfate NaHSO4 is highly water-soluble. It is not a typical neutral salt but chemically an acidic salt, due to substitution of only one acidic proton of the diprotic sulfuric acid. Aqueous solutions of NaHSO4 are highly acidic. It reacts powerfully with strong bases and potent oxidizing agents. It is perfectly steady under normal conditions but decomposes upon exposure to water.

Uses of NaHSO4

We have listed a few uses of NaHSO4 sodium bisulfate below:

Sodium bisulfate is often used as a preservative, in meat processing, food additive, in drugs and dietary supplements. Uses of sodium bisulphate are also extended in pH control, household cleaning products, leather tanning, disinfecting, swimming pools, metal cleaning, and many other applications. Sodium bisulfate was once an essential active ingredient in the toilet bowl cleaners Vanish and Sani-Flush, but now both are discontinued.

1. Sodium bisulfate is used in lowering the pH of water in swimming pools.

2. Used in metal finishing.

3. Used in the chicken house to reduce the concentration of Salmonella.

4. Used as a bleaching agent.

5. Used as a catalyst.

6. Used in the manufacturing of paper products.

7. Used in the water treatment products.

8. Used in paints.

9. Used in agricultural chemicals.

10. Used in velvet cloths.

Chemical Reactions of Sodium Bisulfate

The hydrated sodium bisulfate first dehydrates and then separates from the water molecule which is attached to it at 60°C temperature. It is allowed to cool. Heating it to 290 °C produces sodium pyrosulfate which is nothing but an absolute colourless salt:

2 NaHSO4 → Na2S2O7 + H2O

What is Bisulfate?

Bisulfate is a liquid solution consisting of a white crystalline solid dissolved in water. It is corrosive to metals and tissue. Bisulfate is an ester or salt of sulphuric acid which contains –HSO4 or the ion HSO4 –, the monovalent group (which is a modifier) consisting of, containing, or concerned with the group:

–HSO4 or the ion HSO4

Solved Problem

Question: How is Sodium Bisulfate Made?

Solution: Sodium bisulfate is formed or made as a median in the Mannheim process. It is an industrial process involving the reaction of sodium chloride and sulfuric acid:

NaCl + H2SO4 → HCl + NaHSO4

The liquid sodium bisulfate is sprayed and cooled to help it form a solid bead. The hydrogen chloride gas is dissolved in H2O (water) to form hydrochloric acid. Sodium bisulfate if not for economical interest but can be given rise as an outgrowth of the production of many different mineral acids through the reaction of their sodium salts with more of sulfuric acid:

NaX + H2SO4 → NaHSO4 + HX 

Question: How Do You Neutralise Sodium Bisulphate?

Answer: Sodium bisulfate is not very toxic to the environment if in small quantities, though it should be neutralized first before disposal. We can use a base like sodium carbonate or bicarbonate in aqueous solution.

FAQ (Frequently Asked Questions)

Question 1: Is the Use of Sodium Bisulfate in Plants Safe?

Answer: Vinegar is a neutral acid that is completely harmless to plants when diluted in water. Sodium bisulphate should be used to balance the pH of the water for soil cultivation to prevent over-fertilizing of plants. All the economic pH DOWN products contain potent nitric or phosphoric acid that may raise the level of salt in the soil and burn your plants. Especially seedlings and young plants easily get destroyed from regular watering on them with pH down. Sulfuric, phosphoric and citric acids seem to work well, and it is advisable to use more than one for better buffering. Since plants need phosphorus anyhow, a phosphoric/citric acid mix can be used.

Question 2: What is the Difference Between Sodium Hydrogen Sulphite (Sodium Bisulfite) and Sodium Hydrogen Sulfate (Sodium Bisulphate)?

Answer: Sodium hydrogen sulfite or “sodium bisulfite” (NaHSO3) is used as a preservative to reduce or prevent microbial spoilage, in food processing as a sanitizing agent for food containers and fermentation equipment, as an antioxidant and inhibitor of enzyme-catalyzed oxidative discolouration and non-enzymic browning, and selective inhibitor of undesirable microorganisms in the fermentation industries. The food additive code of sodium hydrogen sulfite is E 222 (the E number is commonly found on food labels).

Sodium hydrogen sulfate or “sodium bisulfate” (NaHSO4) is used as an acidity regulator. E 514 is the food additive code of sodium hydrogen sulfate. Sodium bisulfate will also control browning. It works by lessening the pH to hamper the polyphenol oxidase enzyme. It lowers pH without a sour taste, so it does not change the flavour of the food.

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