Halides and pseudohalides with silver nitrate
potassium bromide Xi
potassium cyanate Xn R 22 S 24/25
potassium thiocyanate Xn R 20/21/22-30 S 13
silver nitrate solution, diluted Xi N R 34-50/53 S(1/2)-26-45-60-61
Instead of potassium salts one can use the corresponding sodium salt. If not all salts are available the experiment can be accordingly adjusted.
Production of silver nitrate solution
test tube rack
for each salt one test tube
- One adds to each test tube a small spatula-tipful of one of the different salts.
- To each salt one adds 2-3 ml of water, the salts dissolve.
- To each salt one adds a couple of drops of silver nitrate solution, various precipitations are produced:
- Chloride, cyanat und thiocyanat cause white precipitations.
- Bromide causes a sallow yellow precipitation (a differentiation to chloride is only possible in exceptionally good lighting conditions).
- Iodide causes a yellow precipitation.
- The halide precipitations form under gentle swaying a rather homogenous suspension which only slowly clarifies, the pseudohalide precipitations are formed very quickly.
One disposes of the suspensions as silver-containing waste. If one does not collect this seperately, then as heavy metal waste, it is not to be discharged into the drainage.
The halides and pseudohalides of silver are insolube and precipitate. In weighing the deposits, one can also determine quantatively the halides/pseudohalides or silver ions.
Precipitation of halides and pseudohalides. From left to right: chloride, bromide, iodide, cyanate, thiocyanate.
The experiment is based on an experiment from the school class.
Concerning the precipitation of cyanide: XII.2.1, "Cyanidnachweis als AgCN", S. 141,