- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Density
- Solubility
- pH
- Chemical properties
- Obtaining
- Presence in nature
- Applications
- In chemical analysis laboratories
- In the destruction of chlorofluorocarbons
- In determining important parameters in wastewater treatment
- To obtain oxalic acid
- To remove unwanted compounds
- Risks
- References
The sodium oxalate is an organic compound consisting of two sodium ions and oxalate ion. Its chemical formula is Na 2 C 2 O 4 or also Na 2 (COO) 2. It is the sodium salt of oxalic acid or ethanedioic acid. Na 2 C 2 O 4 is a white crystalline solid and its aqueous solutions are basic (alkaline).
Sodium oxalate is present in plants and vegetables. In humans, oxalic acid is generated naturally from its conjugated acid, which in turn is produced by certain metabolic processes.
Sodium oxalate Na 2 (COO) 2 solid. Leiem. Source: Wikimedia Commons.
Na 2 C 2 O 4 is used in chemical analysis laboratories as a reducing agent (the opposite of oxidant). Also to allow testing of certain organic compounds during wastewater treatment.
It has been used for the disposal of chlorofluorocarbons (CGC) waste, which damage the ozone layer. It is also a raw material to obtain oxalic acid economically.
Due to the high sodium oxalate content of some edible vegetables, people who have a tendency to form stones or kidney stones should avoid consuming such foods. This is because stones are generally formed from oxalates.
Structure
Sodium oxalate is made up of two sodium Na + cations and one oxalate anion (COO) 2 2 -. The oxalate anion is formed in turn by two COO units - linked through the two carbon atoms: - OOC – COO -.
In solid sodium oxalate, the oxalate anion has a flat shape. This means that both the carbons and oxygens are in the same plane.
Chemical structure of sodium oxalate Na 2 (COO) 2. Author: Benjah-bmm27. Source: Wikimedia Commons.
Nomenclature
- Sodium oxalate
- Disodium oxalate
- Sodium salt of ethanedioic acid
Properties
Physical state
Crystalline white solid.
Molecular weight
134.0 g / mol
Density
2.27 g / cm 3 at 20 ° C.
Solubility
Soluble in water: 3.7 g / 100 mL at 20 ° C.
pH
Its aqueous solutions are basic (alkaline) because the oxalate anion tends to take protons from the water, leaving the OH - ions free.
Chemical properties
It can neutralize acids and the reactions are exothermic, that is, they give off heat.
It serves as a reducing agent and in these reactions generates carbon dioxide CO 2.
It has the property of strongly binding to various metal ions such as ferrous iron ions Fe 2+ and ferric Fe 3+.
Obtaining
According to a source consulted, sodium oxalate can be obtained by oxidizing carbon with oxygen O 2 at a temperature of about 250 ° C in a concentrated solution of sodium hydroxide NaOH.
Presence in nature
Sodium oxalate is present in many plants and vegetables, such as chard, spinach, and rhubarb, and in grains such as soybeans, among many other plant products.
Spinach has a large amount of sodium oxalate. Author: Aline Ponce. Source: Pixabay.
Its conjugated acid, oxalic acid, is produced in the human body by the metabolism of glycolic acid or ascorbic acid. Once produced, it is not metabolized, but is excreted in the urine in the form of oxalate.
Rhubarb contains sodium oxalate. Authors: S. Hermann & F. Richter. Source: Pixabay.
Applications
In chemical analysis laboratories
It is used as a chemical reagent, generally as a reducing agent, for example for the standardization of potassium permanganate solutions, that is, to determine exactly how much sodium permanganate they have.
In the destruction of chlorofluorocarbons
Sodium oxalate has been used for the destruction of chlorofluorocarbons (CFCs). These CFC compounds have been one of those responsible for the destruction of the planet's ozone layer (which protects us from ultraviolet radiation).
In 1996, some researchers proposed the use of sodium oxalate to eliminate them, as it easily reacts with CFCs at temperatures of 270-290 ° C, making them harmless to the ozone layer.
The reaction of sodium oxalate with CFCs can be controlled to obtain halogenated aromatic hydrocarbons that are not harmful to the ozone layer but are useful compounds in the chemical industry.
Such a reaction can also be maximized and convert all CFC into sodium fluoride NaF, sodium chloride NaCl, elemental carbon and carbon dioxide CO 2.
The planet's ozone layer protects us from the sun's ultraviolet rays. Sodium oxalate eliminates the CFC compounds that damage it. Author: One94. Source: Pixabay.
In determining important parameters in wastewater treatment
Sodium oxalate has been found to be useful in measuring the amount and kinds of organic compounds secreted by microorganisms from sludge used to treat wastewater.
The measurement of such compounds is important to determine their function during wastewater treatment, since the ease of separating the sludge from the water depends on them.
Using sodium oxalate avoids the disadvantages of other methods.
To obtain oxalic acid
Crude sodium oxalate from process wastes has been used to produce oxalic acid H 2 C 2 O 4 in large quantities.
The method uses sludge from the Bayer process to treat bauxite (an aluminum ore). In the Bayer process, bauxite is treated with sodium hydroxide NaOH to dissolve the alumina in this mineral.
In the process of dissolving alumina, certain organic compounds present in the mineral, such as humic acids, are attacked by NaOH, generating a large amount of sodium oxalate Na 2 C 2 O 4.
This sodium oxalate is incorporated into a mud with aluminum compounds. To purify it, the whole is dissolved, filtered and passed through an acid-type ion exchange column.
In the column there is a sulfonic acid RSO 3 H resin where Na + metal ions are exchanged for H + hydrogen ions, thus obtaining oxalic acid H 2 C 2 O 4.
RSO 3 H + Na 2 C 2 O 4 ⇔ RSO 3 Na + NaHC 2 O 4
RSO 3 H + NaHC 2 O 4 ⇔ RSO 3 Na + H 2 C 2 O 4
This is an inexpensive process and the oxalic acid obtained is of acceptable purity.
To remove unwanted compounds
The conjugated acid of sodium oxalate, oxalic acid H 2 C 2 O 4, is used to dissolve certain types of debris and scale.
It takes advantage of the characteristic of oxalic acid to convert to oxalate by acting as a complexing or precipitating agent, for example during the processing of waste from various nuclear fuels.
Oxalic acid is also used to remove mineral and iron oxide scale in pipes and other equipment, this is due to its ability to bind strongly both the ferrous ion Fe 2+ and the ferric ion Fe 3+ forming oxalates.
Risks
If directly inhaled or ingested sodium oxalate causes pain in the throat, esophagus and stomach. It causes vomiting, severe purging, weak pulse, cardiovascular collapse, neuromuscular symptoms, and kidney damage.
People who have a tendency to form kidney stones due to accumulation of oxalate in the urine should avoid consuming vegetables with a high content of soluble oxalates such as sodium.
Sodium oxalate in high amounts in food when it reaches the urine binds to the calcium present in it and can cause stones or calcium oxalate stones in the kidneys in people who have a tendency to do so.
The sodium oxalate in some foods can lead to the formation of stones in the kidneys of people with a predisposition to it. Author: Azwer. Source: Pixabay.
References
- US National Library of Medicine. (2019). Sodium oxalate. National Center for Biotechnology Information. Recovered from pubchem.ncbi.nlm.nih.gov.
- Chai, W. and Liebman, M. (2005). Effect of Different Cooking Methods on Vegetable Oxalate Content. J. Agric. Food Chem. 2005, 53, 3027-3030. Recovered from pubs.acs.org.
- Dagani, R. (1996). CFC Destroying Reaction. Chemical & Engineering News Archive 1996, 74, 4, 6-7. Recovered from pubs.acs.org.
- Sajjad, M. and Kim, KS (2016). Extraction of extracellular polymeric substances from activated sludge using sodium oxalate. Int. J. Environ. Sci. Technol. 13, 1697-1706 (2016). Recovered from link.springer.com.
- Jeffrey, GA and Parry, GS (1954). The Crystal Structure of Sodium Oxalate. J. Am. Chem. Soc. 1954, 76, 21, 5283-5286. Recovered from pubs.acs.org.
- Okuwaki, A. et al. (1984). Production of Oxalate by the Oxidation of Coal with Oxygen in a Concentrated Sodium Hydroxide Solution. Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 648-651. Recovered from pubs.acs.org.
- Hefter, G. et al. (2018). Solubility of Sodium Oxalate in Concentrated Electrolyte Solutions. J Chem & Eng Data. 2018, 63, 3, 542-552. Recovered from pubs.acs.org.
- The, KI (1992). Process for the preparation of oxalic acid and sodium hydrogen oxalate from crude sodium oxalate. US Patent No. 5,171,887. Dec.15, 1992. Recovered from freepatentsonline.com.