Sodium thiosulfate. Uses and contraindications Sodium thiosulfate solubility in water

An inorganic compound, sodium salt of thiosulfate acid with the composition Na 2 S 2 O 3. Under normal conditions, it is in the form of its crystalline hydrate Na 2 S 2 O 3 · 5H 2 O, which is colorless crystals; with slight heating it loses water of crystallization. Thiosulfate exhibits strong reducing properties and is capable of forming coordination compounds with metals.

The semi-lethal dose of sodium thiosulfate is 7.5 ± 0.752 g/kg body (for mice). Due to its low toxicity, thiosulfate can be freely used for medical purposes - it is an antidote for poisoning with cyanide and silver compounds.

Sodium thiosulfate is used in photography to dissolve silver bromide, and in the pulp, paper and textile industries to neutralize chlorine residues. Thiosulfate is a reagent for determining the content of iodine, bromine, chlorine and sulfur using the iodometry method. In the food industry, sodium thiosulfate is used as an antioxidant and sequestrant; in the international register of food additives it has code E539.

Physical properties

Pure sodium thiosulfate is a white, heavy powder, but under ordinary conditions it is in the form of its pentahydrate Na 2 S 2 O 3 · 5H 2 O, which crystallizes from solutions in the form of short prismatic or oblong crystals. In dry air, at 33 ° C, it loses moisture, and at 48 ° C, the thiosulfate dissolves in its own water of crystallization.

Receipt

In industry, sodium thiosulfate is synthesized by oxidation of sodium sulfide, hydrosulfide or polysulfides. In addition, one of the common methods is the interaction of sulfur with sodium sulfite:

The addition of sulfur to sulfite suspensions is carried out with constant stirring. The addition of cationic surfactants increases the wetting of sulfur and, accordingly, the reaction rate. The yield of the reaction depends on the temperature, the amount of sulfur and the intensity of stirring. Solutions of sodium thiosulfate are filtered hot, having previously gotten rid of excess sulfur, and when cooled, the hydrate Na 2 S 2 O 3 · 5H 2 O crystallizes from them, which dehydrates at a temperature of 60-105 ° C at atmospheric or reduced pressure. The purity of the product is about 99% and has minor impurities of sulfite and sodium sulfate.

Other industrial methods include treating sodium compounds with sulfur dioxide:

Sodium thiosulfate is also synthesized as a by-product in the production of sulfur dyes, where sodium polysulfides are oxidized by nitro compounds:

Chemical properties

Being in the form of crystalline hydrate under normal conditions, thiosulfate loses water upon low heating:

Further heating causes decomposition of the substance: with the formation of sulfur or sodium pentasulfide (with impurities of other polysulfides):

In a dark place, a thiosulfate solution can be stored for several months, but when boiled it immediately decomposes.

Thiosulfate is unstable to acids:

It is a strong reducing agent:

When interacting with halogens, thiosulfate reduces them to halides:

The latter reaction has found application in analytical chemistry in the titrimetric method of iodometry.

Thiosulfate participates in complexation reactions, binding compounds of certain metals, for example, silver:

Application

Sodium thiosulfate is widely used in photography to dissolve silver bromide from negatives or prints. In the pulp, paper and textile industries, thiosulfate is used to neutralize chlorine residues; it is involved in the dechlorination of water.

In mining, Na 2 S 2 O 3 acts as an extractant of silver from its ores. Thiosulfate is a reagent for determining the content of iodine, bromine, chlorine and sulfur using the iodometry method. Thiosulfate is also an antidote for poisoning with cyanides and silver compounds.

Related Images

Sodium thiosulfate (antichlor, hyposulfite, sodium sulfidetrioxosulfate) - Na 2 S 2 O 3 or Na 2 SO 3 S, sodium salt and thiosulfuric acid. Under normal conditions, it exists in the form of Na 2 S 2 O 3 ·5H 2 O pentahydrate.

Colorless monoclinic crystals.

Molar mass 248.17 g/mol.

Soluble in water (41.2% at 20 o C, 69.86% at 80 o C).

At 48.5 °C it melts in its water of crystallization and dehydrates at about 100 °C.

When heated to 220 °C, it decomposes according to the following scheme:

4Na 2 S 2 O 3 →(t) 3Na 2 SO 4 + Na 2 S 5

Na 2 S 5 →(t) Na 2 S + 4S

Sodium thiosulfate is a strong reducing agent:

Strong oxidizing agents, for example, free chlorine, are oxidized to sulfate or sulfuric acid:

Na 2 S 2 O 3 + 4Cl 2 + 5H 2 O → 2H 2 SO 4 + 2NaCl + 6HCl.

With weaker or slow-acting oxidizing agents, for example, iodine, it is converted into salts of tetrathionic acid:

2Na 2 S 2 O 3 + I 2 → 2NaI + Na 2 S 4 O 6.

The above reaction is very important, as it serves as the basis for iodometry. It should be noted that in an alkaline environment, the oxidation of sodium thiosulfate with iodine can proceed to sulfate.

It is impossible to isolate thiosulfuric acid (hydrogen thiosulfate) by the reaction of sodium thiosulfate with a strong acid, since it is unstable and immediately decomposes:

Na 2 S 2 O 3 + H 2 SO 4 → Na 2 SO 4 + H 2 S 2 O 3

H 2 S 2 O 3 → H 2 SO 3 + S

Molten sodium thiosulfate is very prone to hypothermia.

Receipt.

oxidation of Na polysulfides;

boiling excess sulfur with Na 2 SO 3:

S + Na 2 SO 3 →(t) Na 2 S 2 O 3 ;

interaction of H 2 S and SO 2 with NaOH by-product in the production of NaHSO 3, sulfur dyes, when purifying industrial gases from S:

4SO 2 + 2H 2 S + 6NaOH → 3Na 2 S 2 O 3 + 5H 2 O;

boiling excess sulfur with sodium hydroxide:

3S + 6NaOH → 2Na2S + Na2SO3 + 3H2O

Then, in the above reaction, sodium sulfite adds sulfur to form sodium thiosulfate.

At the same time, during this reaction, sodium polysulfides are formed (they give the solution a yellow color). To destroy them, SO 2 is passed into the solution.

Pure anhydrous sodium thiosulfate can be prepared by reacting sulfur with sodium nitrite in formamide. This reaction proceeds quantitatively (at 80 °C for 30 minutes) according to the equation:

2NaNO 2 + 2S → Na 2 S 2 O 3 + N 2 O

Qualitative analysis.
1. Analytical reactions for sodium cation.

1. Reaction with zinc dioxourane(VI) acetate Zn(UO 2 ) 3 (CH 3 COO) 8 with the formation of a yellow crystalline precipitate (pharmacopoeial reaction - GF) or yellow crystals of tetrahedral and octahedral shape, insoluble in acetic acid (MCA). To increase the sensitivity of the reaction, the test mixture should be heated on a glass slide.

NaCl+ Zn(UO 2) 3 (CH 3 COO) 8 + CH 3 COOH + 9 H 2 O

NaZn(UO 2) 3 (CH 3 COO) 9 9 H 2 O + HCl

Interfering ions: excess K + ions, heavy metal cations (Hg 2 2+, Hg 2+, Sn 2+, Sb 3+, Bi 3+, Fe 3+, etc.). The reaction is used as a fractional reaction after removing interfering cations.

2. Coloring the colorless burner flame yellow (YF).

3. Reaction with picric acid to form yellow, needle-shaped sodium picrate crystals emanating from one point (ISS).

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The reaction is used as a fractional reaction only in the absence of interfering ions (K +, NH 4 +, Ag +).

4. Reaction with potassium hexahydroxostibate(V) K with the formation of a white crystalline precipitate, soluble in alkalis.

NaCl+K
Na + KCl

Conditions for the reaction: a) sufficient concentration of Na +; b) neutral reaction of the solution; c) carrying out the reaction in the cold; d) rubbing a glass rod against the wall of the test tube. Interfering ions: NH 4 +, Mg 2+, etc.

In an acidic environment, the reagent is destroyed with the formation of a white amorphous precipitate of metaantimony acid HSbO 3.

K+HCl
KCl + H 3 SbO 4 + 2 H 2 O

H3SbO4
HSbO 3  + H 2 O

Sodium thiosulfate is a synthetic compound known in chemistry as sodium sulfate, and in the food industry as additive E539, approved for use in food production.

Sodium thiosulfate functions as an acidity regulator (antioxidant), anti-caking agent or preservative. The use of thiosulfate as a food additive allows you to increase shelf life and product quality, and prevent rotting, souring, and fermentation. In its pure form, this substance is involved in technological processes for the production of edible iodized salt as an iodine stabilizer and is used for processing baking flour, which is prone to caking and clumping.

The use of the food additive E539 is limited exclusively to the industrial sphere; the substance is not available for retail sale. For medical purposes, sodium thiosulfate is used as an antidote for severe poisoning and an anti-inflammatory agent for external use.

general information

Thiosulfate (hyposulfite) is an inorganic compound that is the sodium salt of thiosulfuric acid. The substance is a colorless, odorless powder, which upon closer examination turns out to be transparent monoclinic crystals.

Hyposulfite is an unstable compound that does not occur in nature. 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 thiosulfate: synthesis

Sodium sulfate was first obtained artificially in the laboratory using the Leblanc method. This compound is a byproduct of soda production, which is formed by the oxidation of calcium sulfide. Interacting with oxygen, calcium sulfide is partially oxidized to thiosulfate, from which Na 2 S 2 O 3 is obtained using sodium sulfate.

Modern chemistry offers several methods for the synthesis of sodium sulfate:

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 can produce sodium thiosulfate as a by-product of the reaction or in the form of an aqueous solution from which the liquid must be evaporated. An alkaline solution of sodium sulphate can be obtained by dissolving its sulfide in oxygenated water.

The pure anhydrous compound thiosulfate is the result of the reaction of a sodium salt and nitrous acid with sulfur in a substance known as formamide. The synthesis reaction takes place at a temperature of 80 °C and lasts about half an hour; its products are thiosulfate and its oxide.

In all chemical reactions, hyposulfite acts as a strong reducing agent. In reactions with strong oxidizing agents, Na 2 S 2 O 3 is oxidized to sulfate or sulfuric acid, and with weak ones - to tetrathione salt. The oxidation reaction of thiosulfate is the basis of the iodometric method for determining substances.

The interaction of sodium thiosulfate with free chlorine, which is a strong oxidizing agent and toxic substance, deserves special attention. 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.

In industrial conditions, thiosulfate is extracted from gas production waste. The most common raw material is illuminating gas, which is released during the coking process of coal and contains hydrogen sulfide impurities. Calcium sulfide is synthesized from it, which is subjected to hydrolysis and oxidation, after which it is combined with sodium sulfate to produce thiosulfate. Despite the multi-stage process, this method is considered the most cost-effective and environmentally friendly method for extracting hyposulfite.

What you need to know about sodium thiosulfate

Systematic name	Sodium thiosulfate
Traditional names	Sodium disulfide, sodium hyposulfite (sodium) soda, antichlorine
International marking	E539
Chemical formula	Na2S2O3
Group	Inorganic thiosulfates (salts)
Physical state	Colorless monoclinic crystals (powder)
Solubility	Soluble in, insoluble in
Melting point	50 °C
Critical temperature	220 °C
Properties	Reductive (antioxidative), complexing
Dietary Supplement Category	Acidity regulators, anti-caking agents (anti-caking agents)
Origin	Synthetic
Toxicity	Not studied, the substance is conditionally safe
Applications	Food, textile, leather industry, photography, pharmaceuticals, analytical chemistry

Sodium thiosulfate: application

Sodium sulphate was used for a variety of purposes long before the compound was included in food supplements and medications. Antichlorine was used to impregnate gauze bandages and gas mask filters to protect the respiratory system from toxic chlorine during the First World War.

Modern areas of application of hyposulfite in industry:

processing photographic film and recording images on photographic paper;
dechlorination and bacteriological analysis of drinking water;
removal of chlorine stains when bleaching fabrics;
gold ore leaching;
production of copper alloys and patina;
leather tanning.

Sodium sulfate is used as a reagent in analytical and organic chemistry; it neutralizes strong acids and neutralizes heavy metals and their toxic compounds. The reactions of thiosulfate with various substances are the basis of iodometry and bromometry.

Food additive 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 breakdown products. Hyposulfite is involved in technological processes for the production of edible iodized salt and bakery products as an acidity regulator and anti-caking agent.

Additive E539 functions as an antioxidant and preservative in the production of canned vegetables and fish, desserts and alcoholic beverages. This substance is also part of the chemicals used to treat the surface of fresh, dried and frozen vegetables and fruits.

Preservative and antioxidant E539 is used to improve the quality and increase the shelf life of such products:

fresh and frozen vegetables, fruits, seafood;
, nuts, seeds;
vegetables, mushrooms and seaweed, canned in or oil;
jams, jellies, candied fruits, fruit purees and fillings;
fresh, frozen, smoked and dried fish, seafood, canned food;
flour, starches, sauces, seasonings, vinegar, ;
white and cane, sweeteners (dextrose and), sugar syrups;
fruit and vegetable juices, sweet water, low-alcohol drinks, grape drinks.

When producing 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 permissible concentration of E539 in table salt is 250 mg per 1 kg.

In baking, sodium thiosulfate is actively used as part of various additives to improve product quality. Baking improvers are either oxidative or reductive. Anti-caking agent E539 is a restorative improver that allows you to change the properties.

Dough made from dense flour with short-tearing gluten is difficult to process, cakes, does not reach the required volume and cracks during baking. 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 during baking.

At enterprises, an anti-caking agent is added to flour along with yeast immediately before kneading the dough. The thiosulfate content in flour is 0.001-0.002% of its mass, depending on the manufacturing technology of the bakery product. Sanitary standards for the E539 additive are 50 mg per 1 kg of wheat flour.

Anti-caking agent E539 is used in technological processes in strict dosages, so there is no risk of thiosulfate poisoning when consuming flour products. Flour intended for retail sale is not processed before sale. Within normal limits, 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 World Health Organization's list of essential medicines as one of the most effective and safe medicines. It is administered subcutaneously, intramuscularly and intravenously as an injection solution or used as an external agent.

At the beginning of the 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 the cyanide into non-toxic thiocyanates, which can then be safely excreted from the body.

Medical uses of sodium sulfate:

The effect of hyposulfite on the human body when consumed orally has not been studied, so it is impossible to judge the benefits and harms of the substance in its pure form or as part of food products. There have been no cases of poisoning with the E539 additive, so it is generally considered non-toxic.

Sodium thiosulfate and legislation

Sodium thiosulfate is included in the list of food additives approved for use in food production 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 additive is not approved for use in the EU and the USA.

atria thiosulfate Natrii thiosulfas

Na 2 S 2 0 3 -5H 2 0 M. m. 248.17

Sodium thiosulfate is not a natural product; it is obtained synthetically.

In industry, sodium thiosulfate is obtained from gas production waste. This method, despite its multi-stage nature, is economically profitable, since the raw materials are gas production waste and, in particular, illuminating gas formed during the coking of coal.

Illuminating gas always contains an admixture of hydrogen sulfide, which is captured by absorbers, for example calcium hydroxide. This produces calcium sulfide.

But calcium sulfide undergoes hydrolysis during the production process, so the reaction proceeds somewhat differently - with the formation of calcium hydrosulfide.

When oxidized by atmospheric oxygen, calcium hydrosulfide forms calcium thiosulfate.

When the resulting calcium thiosulfate is fused with sodium sulfate or sodium carbonate, sodium thiosulfate Na 2 S 2 0 3 is obtained.

After evaporation of the solution, sodium thio-sulfate crystallizes, which is a pharmacopoeial drug.

In appearance, sodium thiosulfate (II) is colorless transparent crystals with a salty-bitter taste. Very easily soluble in water. At a temperature of 50 °C it melts in its water of crystallization. Its structure is a salt of thiosulfuric acid (I).

As can be seen from the formula of these compounds, the degree of oxidation of the sulfur atoms in their molecules is different. One sulfur atom has an oxidation state of +6, the other -2. The presence of sulfur atoms in various oxidation states determines their properties.

Thus, having S 2- in the molecule, sodium thiosulfate exhibits reducing ability.

Like thiosulfuric acid itself, its salts are not strong compounds and easily decompose under the influence of acids, even such weak ones as carbonic acid.

This property of sodium thiosulfate to decompose by acids to release sulfur is used to identify the drug. When adding hydrochloric acid to a solution of sodium thiosulfate, cloudiness of the solution is observed due to the release of sulfur.

Very characteristic of sodium thiosulfate is its reaction with a solution of silver nitrate. This produces a white precipitate (silver thiosulfate), which quickly turns yellow. When standing under the influence of air moisture, the sediment turns black due to the release of silver sulfide.

If, when sodium thiosulfate is exposed to silver nitrate, a black precipitate immediately forms, this indicates contamination of the drug with sulfides, which, when interacting with silver nitrate, immediately release a precipitate of silver sulfide.

A pure preparation does not immediately darken when exposed to a solution of silver nitrate.

As an authenticity reaction, the reaction of sodium thiosulfate with a solution of iron (III) chloride can also be used. In this case, iron oxide thiosulfate is formed, colored violet. The color quickly disappears due to the reduction of this salt to colorless ferrous iron salts (FeS 2 0 3 and FeS 4 0 6).

When interacting with sodium iodine, sodium thiosulfate acts as a reducing agent. Taking electrons from S 2-, iodine is reduced to I-, and sodium thiosulfate is oxidized by iodine to sodium tetrathioiate.

Chlorine is similarly reduced to hydrogen chloride.

When there is an excess of chlorine, the released sulfur is oxidized to sulfuric acid.

The use of sodium thiosulfate to absorb chlorine in the first gas masks was based on this reaction.

The preparation is not allowed to contain impurities of arsenic, selenium, carbonates, sulfates, sulfides, sulfites, calcium salts.

GF X allows the presence of impurities of chlorides and heavy metal salts within the standard.

Quantitative determination of sodium thiosulfate is carried out using the iodometric method, which is based on the reaction of its interaction with iodine. GF requires a sodium thio-sulfate content in the preparation of no less than 99% and no more than 102% (due to the permissible limit of weathering of the preparation).

The use of sodium thiosulfate is based on its ability to release sulfur. The drug is used as an antidote for poisoning with halogens, cyanogen and hydrocyanic acid.

The resulting potassium thiocyanate is much less toxic than potassium cyanide. Therefore, in case of poisoning with hydrocyanic acid or its salts, sodium thiosulfate should be used as first aid. The drug can also be used for poisoning with arsenic, mercury, and lead compounds; in this case, non-toxic sulfides are formed.

Sodium thiosulfate is also used for allergic diseases, arthritis, neuralgia - intravenously in the form of a 30% aqueous solution. In this regard, GF X provides a 30% solution of sodium thiosulfate for injection (Solutio Natrii thiosulfatis 30% pro injectionibus).

Available in powders and ampoules of 5, 10, 50 ml of 30% solution.

Sodium thiosulfate contains water of crystallization, which easily evaporates, so it should be stored in a cool place, in well-sealed dark glass bottles, since light promotes its decomposition. Solutions become cloudy when standing due to the sulfur released. This process is accelerated in the presence of carbon dioxide. Therefore, flasks or bottles with sodium thiosulfate solutions are equipped with a calcium chloride tube filled with soda lime, which absorbs it.

In medical practice in the form of an injection solution as a detoxifying and desensitizing agent or externally as an insecticidal agent, in veterinary medicine as a remedy against skin diseases, in the pharmaceutical industry in the production of medicines; for the preparation of solutions of sodium thiosulfate 30% for injection.

Sodium thiosulfate is also used

for removing traces of chlorine after bleaching fabrics
for extracting silver from ores;
fixer in photography;
reagent in iodometry
antidote for poisoning: As, Br, Hg and other heavy metals, cyanides (converts them into thiocyanates), etc.
for intestinal disinfection;
for the treatment of scabies (together with hydrochloric acid);
anti-inflammatory and anti-burn agent;
can be used as a medium for determining molecular weights by lowering the freezing point (cryoscopic constant 4.26°)
in the food industry it is registered as a food additive E539.
additives for concrete.
for cleansing tissues of iodine

Description

Physico-chemical properties

Colorless, transparent, odorless crystals

Packing

Bag 40 kg. Package 1 kg. Bag 35 kg. Bag 0.5 kg. 1 kg bag. 5 kg bag. 10 kg bag.

Storage

Packaging: 0.5 kg each; 1 kg; 5 kg; 10 kg; 35 kg; 40 kg; 45 kg in bags or bags made of polyethylene film or packaging paper with a polymer coating.

Storage: In a dry place, in well-packed containers. Shelf life - 5 years.

Pharmacopoeial sodium thiosulfate produced by the Chemical Plant named after. L.Ya. Karpova

Mass fraction, %		Norm
Na 2 S 2 O 3 *5H 2 O		99,0-102,0
calcium		no reaction
sulfides		you stand the test
sulfites and sulfates	Max.	0,01
chlorides	Max.	0,005
heavy metals	Max.	0,001
arsenic, selenium		no reaction
gland	Max.	0,002
alkalinity		absence of pink coloration of phenolphthalein
microbiological purity		corresponds to the State Fund XI issue 2, p. 193

Product Code: 264-01
Availability: In stock

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