Oxalic Acid: Preparation, Properties & Uses |

Oxalic Acid.

It occurs every bit potassium hydrogen oxalate inwards the woods sorrel, rhubarb, together with tomatoes. The insoluble calcium oxalate is constitute inwards roughly stony deposits inwards kidneys together with bladder inwards the human body.

Preparation of Oxalic Acid.

(1) Manufacture. Oxalic acid is made industrially past times heating sodium formate to 400°C.

The sodium oxalate thence formed is dissolved inwards H2O together with calcium hydroxide added to precipitate calcium oxalate. The solution is filtered together with the filtrate treated amongst the calculated quantity of dilute sulphuric acid to divulge the oxalic acid.

Calcium sulphate precipitates, together with oxalic acid is crystallised from the filtrate every bit the hydrate, COOH)2.2H2O

Laboratory Method of Oxalic Acid. In the laboratory, oxalic acid is made past times oxidation of sucrose or molasses amongst concentrated nitric acid inwards the presence of vanadium pentoxide every bit a catalyst.

The -CHOH.CHOH- units acquaint inwards sucrose molecule are split upwardly out together with oxidised to oxalic acid.

Properties of Oxalic Acid.

Physical Properties of Oxalic Acid. When crystallised from water, colourless prismatic crystals of oxalic acid dihydrate, (COOH)2. 2H2O, are obtained. The dihydrate melts at 101.5°C, piece the anhydrous acid melts at 189.5°C. The hydrate acid becomes anhydrous when carefully heated to 150°C. Oxalic acid is an active poison, depressing the key nervous organisation together with causing malfunction of kidneys.

Chemical Properties of Oxalic Acid. The oxalic acid molecule is made of 2 carboxyl groups inwards the straight off union. It gives all the commons reactions of COOH grouping twice. Also, the acid gives roughly peculiar reactions which postulate the cleavage of the weakened linkage betwixt the 2 highly oxidised carbon atoms.

(1) Formation of Mono-and Di-derivatives. Oxalic acid is a much stronger acid than acetic acid together with readily forms 2 serial of salts, esters, acid halides together with amides.

(2) The activity of Heat. When heated at 150C, it decarboxylates to reach formic acid.

(3) Action amongst Glycerol. Oxalic acid reacts amongst glycerol to cast formic acid or allyl alcohol, depending upon experimental conditions.
(4) Action amongst H2SO4. When heated amongst concentrated sulphuric acid, it is decomposed to reach carbon dioxide, carbon monoxide together with water.

(5) Oxidation. It is readily oxidised, for illustration amongst acidified potassium permanganate.

Oxalic Acid Uses.

Uses of oxalic acid.

1. For removing ink stains together with for bleaching straw for hats, since it reduces chocolate-brown ferric compounds to soluble together with close colourless ferrous salts.
2. As a mordant inwards dyeing together with calico printing.
3. In the industry of inks together with metallic polishes.
4. For preparing allyl alcohol together with formic acid inwards the laboratory.
5. In redox Titrations.