Microchem
Microscale Chemistry Experimentation for Teachers
 

9. Gravimetric determination of the water of crystalisation in cobalt chloride (CoCl₂ . 6 H₂O) on an electric hotplate (120 W):
..

Left: Two small vials are balanced on a scale. A sample of pink cobalt chloride is carefully grinded using another vial as a pestle.
Middle: 100 mg of the pinc cobalt chloride powder are transferred into each of the vials. One sample is kept on the electric hotplate until the water of crystalisation is completely decomposed and evaporated from the vial.
A blue solid of  is left.
Right: The sample lost 45 mg from 100 mg.
The reference percentage of crystal water in CoCl₂.6 H₂O is 45 %.