Multiple choice

The chemical used as a fixer in photography is _____.

  1. Borax

  2. Sodium thiosulphate

  3. Sodium sulphate

  4. Ammonium persulphate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sodium thiosulphate (Na2S2O3) is used as a fixer in photography because it dissolves unexposed silver halide crystals from the developed emulsion, making the image permanent and light-fast. Borax is used as a buffering agent, sodium sulphate is a drying agent, and ammonium persulphate is an oxidizer.

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