Memphis daily appeal. [volume] (Memphis, Tenn.) 1847-1886, 1869-01-17
GLASS.
What ii is Made of and How.

The Manufacturer and BaiI9ey saws
The substance known as glass is. when
chemically considered, a very variable
compound The different qualities. how.
ever, agree in one particular; they be-
long to the class called iusoluble salts.
and have all one acid In common. namely.
silieic acid. This lat substance, usually
simply called silex, is found in nature IN
the form Of quartz, either crystalized or
amorphous, as flint, and as fBe sand. In
the last form it is naturally derived from
the disintegratiOn of granite aud other
rocks containing quartz, in which, by at
mOspherie influences and the prolonged
solvent and mechanical action Of water.
the other ingredients have been washed
away. and the more indestructible quartz
PARTICLES are left behind.
This quartz possesses all the chemical
properties Of an acid Ii combines, Ike
all other acids, with bases such as potash,
soda, lime, magnesia, baryta, oxide Of
lead and Of all other metals, and forms
a series of substances which, according
to the adopted nomenclature, are ealleT
silieates, In the same manner as the com
pounds of sulphuric and nitric acids
with the same bases are called sulphates
and nitrates. As all compounds of this
class are called salts, the silieates are,
when chemically considered, as well
salts as the sulphates The distinction
is of a physical and not of a chemical
nature the silicie acid, being.liquefable
not by water but by heat, communicates
this quality to all It's salts with few ex-
ceptiOns; and its compounds are there
fore, as 4 rule, as insOluble as the nitrates
are soluble.
There are two other acids, boraeic and
phOsphoric, which also form a large
number of insoluble salts called b6rates
aud phosphates and the chemist there
fore recognizes also borax or a phOs-
phate glass but IN common language,
the name Of glass is exclusively applied
to the silieates. Our common window
glass has simply soda and lime as bases
and is therefore a mixture of two silie-
ates, one of soda and one of lime.
Glass made with quartz and soda alone
is of brilliant lustre and easily fusible
but it has a bluish-green tint, and does
not completely resist the action of sur
and rain, which, in the course Of time
furnishes It's brilliant, smooth surface
Glass made with quartz and lime alone
is much harder, not so easily fusible, anC
perfectly eolOrless it resists the actor
of sun and rain better The cOmbina
tion of the two has heen found BY expe
rienee to possess great advantages oTel
either of them alone; except for speeia
purposes.
! Potash is generally added to promOt
the fusibility and eolorless Transparent.
of the compound. as she silieate of pet
ash is still more fusible than thst o
soda, and is perfectly colOrless. How
ever, as it does not possess the briliianci
or lustre of the soda glass, the quantit
added must not be t5o large, as in tha
case the beauty of che product is i'm
paired.
The common formula for German
sheet glass Is as follows:
Giauber salts (sul phate OF sodal......-... 81 81
Sometimes saltpetre (nitrate of pOtas
sa) is used in place Of one Of the twl
soda compounds mentioned.
1t is clear that during fusion the ear
bonic, sulphurie, and nitric acids are ex
PEELED, as they cannot withstand tn
/ high temperature necessary for the fU
sion of the silieie acid. This is the tru
cause of the apparent. strength Of th'
silicie acid. 1t drives all other acid,
out, not by reason of stronger afhnitiei
or because sit is the strongest -;
statement usually made in the books
but simply because the other acids can
not withstand the temperature required
for the liqUefaetion necessary to tn
chemical activity of silieic acid.