hypophosphorous acid : Antioxident, preparation , physical & chemical property , uses , storage , incompatibility

 

 Antioxidant

 a substance which prevent the oxidation of product called antioxidant.
 Antioxidant are chemically reducing agent antioxidant can also call at preservative in the sense that they preserve a product being oxidized.

Ideal properties of antioxidant

* it should prevent the oxidation of product 

* it should be effective in low concentration.

* it should be non-toxic and not irritant.

* it should not affect colour order and taste  of preparation .

*it should be physiologically innert.

Example of antioxidant

* hypophosphorous acid 

*Sulphur Dioxide

 *sodium bisulphate

 *sodium metabisulphate 

*sodium thiosulphate 

*nitrogen 

* sodium nitrite



Hypophosphorus acid [H₃PO₂]


Mol.weight - 66

Hypophosphorous acid is a monobasic and reducing agent it is a colourless or slightly yellow order liquid containing 32 to 32% of hypophosphorous acid it is conventionally prepared by treating NaH₂PO₂ with an Ion exchange resin . the water free acid forms deliquesc crystal hypophosphorous acid contsins only one ionizable hydrogen therefore it reacts as a mono protic acid and is assayed  by titrating against 1N Sodium Hydroxide to a methyl orange end point.

Preparation

It is prepared by decomposing a boil aqua solution of calcium hypophosphorous with oxalic acid.

Ca(PH₂O₂)₂ + 2HOOH → CaC₂O₄ + 2H₃PO₂


Physical property

* hypophosphorous acid is a colourless ,
odourless , crystalline solid .

*it is miscible with water alcohol and Ether.

 *it has melting point 26.5 ℃

Chemical property


* it is titrated with Sodium Hydroxide mixing indicator methyl orange.

* it reacts with molecular iodine to form iodine and decolourises acidic solution of potassium permanganate immediately.

H₃PO₃ + 2I₂ + 2H₂O → 4HI + H₃PO₄

5H₃PO₂ + KMnO₄ + 6H₂SO₄ → 2K₂SO₄ + 4MnSO₄
                                                       + 5H₃PO₄ + 6H₂O



Chemical incompatibility

Combination of hypophosphorous acid with oxidizing agent such as nitrates , chlorates , ,permagnets form explosive mixtures in concentrated amount . in dilute solution it is a very effective antioxidant.

Storage condition

It must be kept in tightly closed container.

Uses

* hypophosphorous acid is used as an antioxidant .

* Earlier hypophosphorous were used in tonics.

* it prevents the formation of free iodine in diluted hydriodic acid and hydrochloric acid syrup.

* it also prevents the formation of both ferric ions and Molecular iodine in ferrous iron syrup.

* Salts of hypophosphorous acid example Sodium and ammonium hypophosphite are presented as a preservative in Central Food and preparation .

* it is used in emulsifier.

* it is powerful reducing agent.




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