In photography, sodium, thisulphate is used as

Options

A. Complexing agent
B. Oxidising agent
C. Reducing agent
D. None of these

Answer

A

Explanation

In order to make the images permanent, it is necessary to remove the unreduced silver bromide from the surface of the developed film. This operation is called fixing of image. Fixing is done by dipping the developed film or plate in sodium thiosulphate (hypo) solution. The hyposoluiton dissolves the undreduced silver bromide by forming a complex.
Thus sodium thiosulphate act as a complexing agent.
`AgBr +2Na_(2)S_(2)O_(3)rarr underset(("soluble"))underset("Sodium argentothiosulphate")(Na_(3)[Ag(S_(2)O_(3))_(2)]) +NaBr`