Division 4.2.2 Dry ashing

Weigh out 5 to 10 g of sample, according to assumed quantity of calcium, into a platinum dish (3.2).

Dry in muffle furnace or on hot place or under infra-red lamp, on a gentle, slow heat to avoid losing matter through boiling over. Place residue in muffle furnace preheated to 400 °C and incinerate for at least six hours.

If cadmium is present, a few drops of phosporic or sulphuric acid should be added.

If the ash is not completely white, it should be wetted with a few drops of nitric acid, the product should be dried completely under the infra-red lamp until there are no more white fumes, and treatment in the muffle furnace should be repeated for at least four hours.

Mix the ash with 1 ml nitric acid, transfer to the 50 ml volumetric flask and make up to the mark with water.