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Sodium thiosulfate is a synthetic compound known in chemistry as sodium sulphate, and in the food industry as additive E539, approved for use in food production.
Sodium thiosulfate acts as an acidity regulator (antioxidant), anti-caking agent or preservative. The use of thiosulfate as a food additive allows you to increase the shelf life and product quality, prevent rotting, souring, fermentation. In its pure form, this substance is involved in the technological processes for the manufacture of food iodized salt as an iodine stabilizer and is used to process bakery flour, which is prone to caking and clumping.
The use of food additive E539 is limited exclusively to the industrial sector, the substance is not available for retail sale. For medical purposes, sodium thiosulfate is used as an antidote for severe poisoning and as an external anti-inflammatory agent.
general information
Thiosulfate (hyposulfite) is an inorganic compound that is the sodium salt of thiosulfuric acid. The substance is a colorless, odorless powder, which on closer examination turns out to be transparent monoclinic crystals.
Hyposulfite is an unstable compound that does not occur naturally. The substance forms a crystalline hydrate, which, when heated above 40 ° C, melts in its own crystalline water and dissolves. Molten sodium thiosulfate is prone to supercooling, and at a temperature of about 220 ° C, the compound is completely destroyed.
Sodium thiosulphate: synthesis
Sodium sulphate was first obtained artificially in the laboratory by the Leblanc method. This compound is a by-product of soda production that results from the oxidation of calcium sulfide. Interacting with oxygen, calcium sulfide is partially oxidized to thiosulfate, from which Na is obtained using sodium sulfate.2S2O3.
Modern chemistry offers several ways to synthesize sodium sulphate:
- oxidation of sodium sulfides;
- boiling sulfur with sodium sulfite;
- interaction of hydrogen sulfide and sulfur oxide with sodium hydroxide;
- boiling sulfur with sodium hydroxide.
The above methods make it possible to obtain sodium thiosulfate as a by-product of the reaction or as an aqueous solution from which the liquid must be evaporated. You can get an alkaline solution of sodium sulphate by dissolving its sulfide in oxygenated water.
The pure anhydrous compound of thiosulfate is the result of the reaction of the sodium salt of nitrous acid with sulfur in a substance known as formamide. The synthesis reaction proceeds at a temperature of 80 ° C and lasts about half an hour, its products are thiosulfate and its oxide.
In all chemical reactions, hyposulfite manifests itself as a strong reducing agent. In reactions with strong oxidants Na2S2O3 oxidized to sulfate or sulfuric acid, with weak ones to tetrathione salt. The oxidation reaction of thiosulfate is the basis of the iodometric method for determining substances.
Special attention deserves the interaction of sodium thiosulfate with free chlorine, which is a strong oxidizing agent and a toxic substance. Hyposulfite is easily oxidized by chlorine and converts it into harmless water-soluble compounds. Thus, this compound prevents the destructive and toxic effects of chlorine.
Under industrial conditions, thiosulfate is extracted from gas production waste. The most common raw material is lighting gas, which is released during coal coking and contains impurities of hydrogen sulfide. Calcium sulfide is synthesized from it, which is subjected to hydrolysis and oxidation, after which it is combined with sodium sulfate to obtain thiosulfate. Despite the multi-stage nature, this method is considered the most cost-effective and environmentally friendly method for extracting hyposulfite.
| Systematic name | Sodium thiosulfate (Sodium thiosulfate) |
|---|---|
| Traditional Appellations | Sodium sulfate, hyposulfite (sodium) soda, antichlor |
| International marking | E539 |
| Chemical formula | Na2S2O3 |
| Group | Inorganic thiosulfates (salts) |
| State of aggregation | Colorless monoclinic crystals (powder) |
| Solubility | Soluble in water, insoluble in alcohols |
| Melting temperature | 50 ° C |
| Critical temperature | 220 ° C |
| Materials | Reducing (antioxidant), complexing |
| Dietary Supplement Category | Acidity regulators, anti-caking agents (anti-caking agents) |
| Origin | Synthetic |
| Toxicity | Not tested, the substance is conditionally safe |
| Areas of use | Food, textile, leather industry, photography, pharmaceuticals, analytical chemistry |
Sodium thiosulfate: application
Sodium sulphate has been used for a variety of purposes long before its inclusion in food supplements and medicines. Antichlor was impregnated with gauze bandages and filters of gas masks to protect the respiratory organs from poisonous chlorine during the First World War.
Modern areas of application of hyposulfite in industry:
- film processing and fixing images on photographic paper;
- dechlorination and bacteriological analysis of drinking water;
- removal of chlorine stains when bleaching fabrics;
- leaching of gold ore;
- production of copper alloys and patina;
- skin tanning.
Sodium sulphate is used as a reagent in analytical and organic chemistry, it neutralizes strong acids, neutralizes heavy metals and their toxic compounds. The interaction reactions of thiosulfate with various substances are the basis of iodometry and bromometry.
Food supplement E539
Sodium thiosulfate is not a widely used food additive and is not freely available due to the instability of the compound and the toxicity of its degradation products. Hyposulfite is involved in technological processes for the production of food iodized salt and bakery products as an acidity regulator and anti-caking agent (anti-caking agent).
Additive E539 performs the functions of an antioxidant and preservative in the manufacture of canned vegetables and fish, desserts and alcoholic beverages. This substance is also part of the chemicals that treat the surface of fresh, dried and frozen vegetables and fruits.
The preservative and antioxidant E539 is used to improve the quality and increase the shelf life of such products:
- fresh and frozen vegetables, fruits, seaweed;
- candied fruits, dried fruits, nuts, seeds;
- vegetables, beans, mushrooms and seaweed preserved in vinegar or oil;
- jams, jellies, marmalades, candied fruits, fruit purees and fillings;
- fresh, frozen, smoked and dried fish, seafood, canned food;
- flour, starches, sauces, seasonings, vinegar, mustard;
- white and cane sugar, sweeteners (dextrose and fructose), sugar syrups;
- fruit and vegetable juices, soft drinks, soft drinks, beer, cider, grape wines.
In the manufacture of table iodized salt, the food additive E539 is used to stabilize iodine, which can significantly extend the shelf life of the product and preserve its nutritional value. The maximum allowable concentration of E539 in table salt is 250 mg per 1 kg.
In the baking business, sodium thiosulfate is actively used as part of various additives to improve product quality. Bread improvers are oxidative and reductive. Anti-caking agent E539 refers to improvers with a restorative action that allow you to change the properties of wheat flour.
Dough made from dense flour with short-tearing gluten is difficult to process, cakes, does not reach the required volume and cracks during baking. The anti-caking agent E539 destroys disulfide bonds and structures gluten proteins, as a result of which the dough rises well, the crumb becomes loose and elastic, and the crust does not crack when baking.
At enterprises, an anti-caking agent is added to flour along with yeast immediately before dough is kneaded. The content of thiosulfate in flour is 0,001-0,002% of its mass, depending on the technology of manufacturing a bakery product. Sanitary and hygienic standards for the additive E539 are 50 mg per 1 kg of wheat flour.
Anti-caking agent E539 is used in technological processes in a strict dosage, so there is no risk of thiosulfate poisoning when using flour products. Flour intended for retail sale is not processed before sale. Within the normal range, the supplement is safe and does not have a toxic effect on the body.
Use in medicine and its effect on the body
Soda hyposulfite is included in the list of essential medicines of the World Health Organization as one of the most effective and safe medicines. It is injected under the skin, intramuscularly and intravenously as an injection or used as an external agent.
In the early twentieth century, sodium thiosulfate was first used as an antidote for hydrocyanic acid poisoning. In combination with sodium nitrite, thiosulfate is recommended for particularly severe cases of cyanide poisoning and is administered intravenously to convert cyanide to non-toxic thiocyanates that can then be safely excreted from the body.
Medical use of sodium sulphate:
- anti-inflammatory, anti-burn and antiparasitic agent;
- antidote for an overdose of lidocaine, cyanide poisoning, heavy metals and their salts;
- cleansing and disinfection of the intestines;
- treatment of calciphylaxis in patients with kidney damage;
- prevention of extravasation and tissue destruction during chemotherapy;
- treatment and prevention of fungal diseases.
The effect of hyposulfite on the human body when taken orally has not been studied, therefore it is impossible to judge the benefits and harms of the substance in its pure form or as part of food. There have been no cases of poisoning with the E539 additive, so it is considered to be non-toxic.
Sodium thiosulfate and legislation
Sodium thiosulfate is included in the list of food additives approved for use in the manufacture of food products in Russia and Ukraine. Anti-caking agent and acidity regulator E539 are used in accordance with established sanitary and hygienic standards exclusively for industrial purposes.
Due to the fact that the effect of the chemical on the human body when administered orally has not yet been studied, the E539 supplement is not approved for use in the EU and the USA.