Thiosulfuric acid

Monosulfanmonosulfonsäure

Colorless oily liquid

Liquid

• 0.6
• 1.74

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The thiosulfuric acid is an oxo acid of sulfur or a thioacid of the sulfuric acid which is formally derived from the sulfuric acid, wherein an oxygen atom is replaced by a sulfur atom.

Representation

The appearance of the water- free acid may be carried out in diethyl ether at -20 ° C by the reaction of hydrogen sulfide ( H2S) with sulfur trioxide (SO3). Above a temperature of -10 ° C decomposes thiosulphuric back into H2S and SO3. Without ether, however, which is also easily decomposable Lewis adduct H2S · SO3.

Properties

Thiosulfuric acid is present in the SH- form. The tautomeric structure with a double bond between the sulfur atoms is more energetic to 41 kJ / mol. The two sulfur atoms have an average oxidation number of 2. H2S -1S 5 O3

Salts of thiosulphuric

The salts of the thiosulphuric that thiosulfate, are stable in water. They can be prepared by boiling sulphite with sulfur in accordance with the following equation:

Acidified thiosulphate decompose to sulfur deposition:

In photography, sodium thiosulfate has practical significance as a fixer. Thiosulfate ions have a reducing effect. In bleachers it is used for the removal of chlorine from chlorine-bleached tissue. Quantitative reaction with iodine to tetrathionate ion S4O62 - is used in analytical chemistry ( iodometry ).