"Dry chemistry" experiment
How to make salts change their color without any liquid
We’re all used to chemical reactions taking place in solutions or in a gaseous state, but this is not always the case. In this colorful experiment we carry out a chemical reaction using dry substances.
Reagents and equipment:
- copper(II) chloride dihydrate;
- cobalt (II) chloride hexahydrate;
- potassium thiocyanate;
- 2 ceramic cups;
- pestle for grinding.
In the ceramic cups, mix potassium thiocyanate with copper (II) chloride dihydrate and cobalt (II) chloride hexahydrate, and grind.
There’s a whole branch of analytical chemistry called “Dry chemistry”. When certain substances are ground together, characteristic colored compounds form. In this experiment, when potassium rhodanide is ground with copper (II) chloride dihydrate, dark grey copper (II) thiocyanate forms. When potassium rhodanide is ground with cobalt (II) chloride hexahydrate, blue-purple tetrarhodanocobaltate (II) forms. We should note that the initial salts contain crystallized water, so the reaction partially takes place in a solution.
2KSCN + CuCl₂∙2H₂O → Cu(SCN)₂ + 2KCl + H₂O
CoCl₂∙6H₂O + 4KSCN → K₂[Co(SCN)₄] + 2KCl + 6H₂O
Wear protective gloves and glasses.
Warning! Only under professional supervision.