SUGAR OF LEAD. 207 
constantly stirring the mixture till they are duly incor- 
porated. This plaster is applied in excoriations of the 
skin, slight wounds, and other sores. 
Sugar of Lead is a preparation either from the metal 
itself, or from white lead and distilled vinegar. It is 
usually observed in the form of small slender crystals, 
which have a glossy appearance like satin. This sub- 
stance is employed, in considerable quantity, by dyers 
and calico printers ; and is the basis of a liquid fre- 
quently used in medicine, called Goulard, or Goulard's 
Extract. Although in itself a most virulent poison, it 
is often used by unprincipled dealers for correcting the 
rancidity of oil of almonds and olive oil ; and a similar 
pernicious fraud is practised by dissolving a portion of 
it in wines which are becoming acid, in order to correct 
their acidity. These frauds, however, are easily de- 
tected by preparations or tests, which are sold by che- 
mists for that purpose. Perhaps the best and simplest 
test is Harrogate water : a little of this poured into the 
suspected compound will discover the presence of lead 
by giving to the fluid a dark brown or blackish tinge. 
The following is a pleasing experiment. Dissolve an 
ounce of sugar of lead in about a quart of water ; filter 
the solution through a piece of blotting paper, and put 
it into a glass decanter, suspending in it a piece of zinc 
by a brass wire. A decomposition will take place ; the 
lead will be set at liberty, and will attach itself to the 
zinc, forming there a sort of metallic tree. 
It has been stated that silver is usually a component 
part of lead ore. To disengage this, where the quantity 
is sufficient to repay the expense, the lead, after it has 
been smelted, is subjected to the action of what is called 
a refining furnace. A continued blast of fresh air is 
thrown upon its surface by means of large bellows, 
while the lead is kept in a state as intensely hot as pos- 
sible. This by degrees converts the lead into a yellow- 
scaly oxide or dross. The oxide, thus formed, is driven 
off from the melted metal as it rises, and the silver is 
