The substance, known in commercial language by the name of _White Lead_,
has received at different times, very various appellations, in
consequence of the fluctuating opinions which have prevailed respecting
its composition. Thus it has been successively styled a _sub-acetate_,
an _oxide_, and a _sub-carbonate_; of which the last is unquestionably
the correct name. In the large way it is prepared by exposing sheets of
metallic lead to the fumes of vinegar. The sub-carbonate so produced
appears as a white, brittle, and scaly substance, on the surface of the
lead; which is scraped off, and afterwards ground in mills fitted for
the purpose. Formerly, it was ground dry, and the workmen suffered
severely from the operation; it is now ground in water, and the
sub-carbonate is afterwards dried in earthen pans placed in stoves,
heated by means of flues; still, however, persons employed in grinding
white lead, as well as painters[375] who are constantly using it,
occasionally suffer severely, from the want of cleanliness in not
washing their hands before eating, by which some of the white lead is
introduced into the stomach with their food.