Question

Sodium thiosulphate is used in photography:

• A. as $AgBr$ grain is reduced to non-metallic silver
• B. to convert metallic silver into silver salt
• C. to remove reduced silver
• D. to remove undecomposed $AgBr$ in the form of $N{a}_3\left[Ag\right(S_2{O}_3{)}_2]$ (a complex salt)

Answer 1

Answer: (D)

to remove undecomposed $AgBr$ in the form of $N{a}_3\left[Ag\right(S_2{O}_3{)}_2]$ (a complex salt)

In photography, undecomposed AgBr is removed with the help of sodium thiosulphate, i.e., hypo.

$\underset{sodiumbromide}{AgBr}+\underset{sodiumthiosulphate}{2N{a}_2{S}_2{O}_3}\to \underset{sodiumargerntothiosulphate}{N{a}_3\left[Ag\right(S_2{O}_3{)}_2]}+NaBr$