Precipitation and reduction of thiosulfate with silver nitrate

Chemicals needed

distilled water

sodium thiosulfate

silver nitrate solution, diluted  Xi   N    R 34-50/53     S (1/2)-26-45-60-61

Necessary equipment

test tube

Test procedure

• One puts a spatula-tipful of sodium thiosulfate in the test tube and dissolves this with approx. 1 ml of water.
• Now one adds 2-3 drops of silver nitrate. A white sediment is precipitated which immediatly sinks and leaves behind a clear solution. The color of the sediment yellows and then quickly becomes black.

Disposal

Elucidation

At first poorly soluble silver thiosulfate is precipitated, this then reacts quickly with water to form black silver sulfide and sulphuric acid.

S2O32- + 2 Ag+ -->  Ag2S2O3

Ag2S2O3 + H2O --> AgS + H2SO4

Photos

Precipitation of silver thiosulfate/sulfide

Literature

derived from experiment 3., "Nachweis mit AgNO3", p.126,[7]