bone ash

Bone-ash varies considerably in price, but of late samples containing 70 per cent of phosphates have sold as low as £4: 10s.

The floor of the muffle is protected with a layer of bone-ash, which absorbs any oxide of lead that may be accidentally spilt.

The buttons are removed from the cupel with a pair of pliers and then brushed to remove adherent litharge and bone-ash.

When heated in a closed retort, bones are not converted into bone-ash, but into a body called bone-char.