Need sodium thiosulphate pentahydrate?
We supply sodium pentahydrate in 1kg containers, with discounts available for bulk orders over 4 items
We also supply sodium thiosulphate 0.1M and 0.01M
With all our products, we offer further options including custom labelling and specific pack sizes
How is sodium thiosulphate used to treat water?
This compound can be used to dechlorinate water, such as in swimming pools, spas and aquaria, reducing the concentration of chlorine. The same process can also be used in water treatment plants to clean backwash water before it’s released back to rivers.
Sodium thiosulphate can also be used to test bleach
Sodium thiosulphate is used during pH tests conducted in bleach products. This compound can neutralise the colour-removing properties of bleach, allowing the pH tests to be conducted using common pH indicators. The reaction involves reduction of bleach’s active ingredient hypochlorite, with thiosulphate being oxidised to sulphate.
4 NaClO Na2S2O3 2 NaOH → 4 NaCl 2 Na2SO4 H2O
Uses of sodium thiosulphate in the lab
This compound also reacts with bromine, removing free ions from solution. For this reason, sodium thiosulphate is commonly used in chemistry labs to ensure safe disposal of bromine-containing solutions. It also works with iodine and many other strong oxidisers.
Chemical reactions involving sodium thiosulphate
At temperatures above 300 degree Celsius, sodium thiosulphate can decompose to sodium sulphate and sodium polysulphide.
4 Na2S2O3 → 3 Na2SO4 Na2S5
Typically, most thiosulphate salts also decompose in the presence of acids. Even in the presence of weak acids, sodium thiosulphate is decomposed to sulphur dioxide, sulphur and water. This is known as a clock reaction: as the sulphur reaches a certain concentration, the solution goes from colourless to yellow. It’s typically used to show rate of reaction in chemistry school labs.
Na2S2O3 2 HCl → 2 NaCl S SO2 H2O
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