Synthesis of Sodium thiosulfate

3 g of sodium sulfite and 1 g of sulfite are suspended in 30 mL of water with stirring, the mixture is left to reflux and stir for 2 hours. The mixture is filtered and the filtrate is concentrated on a hot plate till crystals form. The crystallized slurry is then cooled down in an ice bath and some ethanol is added to crystallize the product out and then filtered. The procedure is repeated twice. The product is obtained in a pentahydrated form.

Na2SO3 + S = Na2S2O3


The reflux

The mixture of reflux

Removal of the unreacted sulfur

Spontaneous crystallization of the filtrate

Crystallization of the filtrated solution

Addition of the ethanol

The crystallized product

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