bone ash and phosphates are the sources of this food element.
Iron which has been in contact with the bone ash of burnt corpses has certain characteristics.
When entirely surrounded with bone ash objects are well preserved, and only covered with a thin layer of oxide.
Cupellation, on the other hand, collects them in the bone ash, of which the cupel is composed.
Phosphorus is obtained from bone ash and from phosphate rock which is widely distributed over the surface of the earth.
It may be said, roughly, to consist of the constituents of true porcelain plus a proportion of bone ash.
The bone ash is moistened with water, stamped in a cupel mould, and allowed to dry slowly.
It is the chief mineral constituent of bones of animals, and bone ash is therefore nearly pure calcium phosphate.