Question

Hypo is used in photography because it is :

• A. A strong reducing agent
• B. A strong oxidizing agent
• C. A strong Complexing agent
• D. Photo sensitive Compound

Answer 1

Answer: (C)

A strong Complexing agent

Option (C) is correct.
Hypo is used in photography because it is a strong complexing agent.
Sodium thiosulfate is used as a fixer in photography. The negative plate or film obtained at the end of photographic development with a reducing agent (i.e., potassium ferrous oxalate, pyrogallol) contains $AgBr$ which has not been light-activated and reduced to $Ag$ metal. This is treated with sodium thiosulfate solution so that $AgBr$ is removed as a soluble complex compound.