The oxalic acid is a carboxylic acid with the formula H2C2O4 can also be described as HOOCCOOH, it is a saturated organic acid, normal chain, considered very strong. Among its most important properties are that it is soluble in alcohol and water, crystallises in water in dihydrated form with the formula C2H2O4.2H2O, its hydrated melting point is 101,5 0C. When heated, it decomposes, releasing carbon dioxide (CO2), carbon monoxide (CO) and water.
It occurs naturally as calcium or potassium oxalate, in roots and rhizomes of many plants, it is present in small quantities in many foods, such as cocoa, nuts, beans and also in the leaves of many plants such as spinach, parsley, chard, etc....
There are several ways to produce oxalic acid industrially, one of them is by oxidation of carbohydrates such as starch, it can also be produced with carbon monoxide and sodium hydroxide, but the most commonly used industrially are the first with two successive oxidations, using nitric acid and oxygen from the air, and the second from sodium methanoate.
Its main physical characteristics are: bitter taste, colourless crystalline solid, partially soluble in water, ethanol and solvents.
Uses of oxalic acid
Among the main uses and applications of oxalic acid dihydrate are:
- Treatment of metal surfaces.
- Rust removal on metalsespecially on chrome-plated parts, widely used on bicycles.
- In construction it is used for polishing floorsmarble and other surfaces.
- In navigation, for fibreglass cleaning.
- At beekeeping eradicates the varroa mite that attacks bees.
- Bleaching and protection of textiles, wood and leather.
- Fixation of dyestuffs in the wool fabric.
- Plastics manufacturing.
- In gravimetry, it is used for the precipitation of silver, gold, copper, mercury, etc.
- As a cleaning agent for bathrooms, kitchens, tiles, floors, etc. in household and industry.
- In the laundry it is used for stain removal and bleaching.
OXALIC ACID OR ETHANEDIOIC ACID
|1900 kg/m31.9 g/cm3
|374.65 K (102 °C)
|638.15 K (365 °C)
|462.65 K (190 °C)
|9.5 g/100 mL (15 °C)
Precautions for use of oxalic acid dihydrate
Although its use is very common, it must be taken into account that we are talking about an acid, and therefore all necessary precautions must be taken in its handling, always wearing gloves and avoiding any contact with the material. It causes strong irritations in the mouth, oesophagus, stomach and causes renal damage, in high doses it is lethal because it creates renal obstruction and convulsions, it is the main component of renal calculi. It is easily absorbed through mucous membranes and skin, causing blood circulation disorders and kidney damage. It is a severe eye irritant and prolonged contact causes irreversible damage.