calx

He then showed by experiment that when calx of iron is heated with hydrogen, the hydrogen disappears and the metal iron is produced.

Heat recovers the pure air, and the mercury, leaving the calx of the impure metal.

All transparent enamels are made opaque by the addition of calx, which is a mixture of tin and lead calcined.

The old chemists have affixed the name of calx not only to metals in this state, but to every body which has been long exposed to the action of fire without being melted.

To deny this would be equivalent to a denial that the Latin verb calcare came from calx, 'the heel.'