Some use the following as more direct:-- In a
small evaporating dish place say one ounce of lead; cover it with
muriatic acid; dissolve the lead over a spirit lamp, add a little
water, and let it settle; draw it off into another glass vessel,
and add five or six drops of the solution of potash. If the lead is
suitable for glass-makers, the solution will be of a light, clear,
greenish color; if of a blue or purple shade, it is not suitable for
flint-glass.
SAND, OR SILEX.
In the manufacture of glass it is essential
that the silex should be perfectly pure, as the slightest mineral
taint affects the color.
At first the New England factories got their
sand from Demerara, brought as ballast, and the quality was good.
During the War of 1812 this source of supply was cut off, but Plymouth
beach provided for the wants of the manufacturers, until a better sand
was discovered at Morris River, N.J., though
not up to the full requirement of the art. For ten years past,
Berkshire County, Mass., has furnished
sand; the best quality is owned by G. W. Gordon,
Esq. By thorough washing, and passing it through fine sieves, and proper
packing, he now commands the market, and delivers it ready for use.
The purity has been tested, as shown by the following extract from a
report by Professor A. A. Hayes, M.D., of Boston, Massachusetts State
Assayer, of the result of analyses of three samples of Berkshire sand,
taken from three different locations owned by Mr. Gordon, viz.:--
"For the manufacture of glass, the slight amount
of earth, in mica and tourmaline, contained in these samples, is of no
account, the impurity being such oxides as color glass. The analyses
therefore give only the proportion of coloring oxides; and, for simplicity
of statement, the total weight of coloring oxide in each sample is
determined in one part or pound.
|
