A
naturally occurring white, lustrous metal, widely distributed in nature,
but the total amount is quite small when compared with other metals,
constituting only some 0.05 parts per million of the Earth's crust.
Practically all sulphides of lead, copper, and zinc contain some silver.
Obtained
from crushed silver bearing ore. The actual method of recovery from
the ore depends on which metal is predominant in the ore but normally
ends by electrolysis using one of two techniques, either the Moebius
or Thum Balbach systems. The chief difference being that the electrodes
are positioned vertically in the Moebius system and horizontally in
the Thum Balbach.
As
a food additive it is used solely for external decoration where it can
be found on chocolate confectionery, in the covering of dragées
and the decoration of sugar-coated flour confectionery.
Long,
regular consumption can lead to kidney damage and a blue-grey discoloration
of the eyes, nose and nasal septum, throat and skin.
Not permitted in
Australia.