The ancients were acquainted with a mineral to which they gave the name
of _Cadmia_,[315] from Cadmus, who first taught the Greeks to use it.
They knew that when melted with copper it formed brass; and that when
burnt, a white spongy kind of ashes was volatilized, which they used in
medicine.[316] This mineral contained a good deal of zinc; and yet there
is no proof remaining that the ancients were acquainted with that metal.
It has a brilliant white colour, with a shade of blue, and is composed
of a number of thin plates adhering together; its specific gravity is
7·1. When strongly heated in a crucible, it quickly goes into fusion,
absorbs the oxygen of the atmosphere, and burns with a beautiful white
flame, inclining to green, and extremely brilliant. The oxide of zinc
thus formed, is diffused through the atmosphere, and is there condensed
into extremely light flakes of a beautiful white appearance. This oxide
was formerly known under the fanciful names of _nihil album; lana
philosophorum, &c._
In its metallic state it is quite inert; but late experiments by
_Vauquelin_ and _Deyeux_, have proved that it is very easily acted upon
by water, the weakest vegetable acids, some saline substances, and
butter; a fact which is hostile to the proposal of employing this metal
for the manufacture of culinary utensils.