The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1838-10-12 00:00:00

soda. Like potassium, soda possesses a remarkable facility
of oxidation. It is, on exposure to the air, immediately con-
verted into a white powder, which is soda. The metal is of a
still more beautiful appearance than potassium, and when
cut, it ranks, among the metals, only after silver, for the pu-
rity of its colour. 1 mentioned that the great advantage of
the metallic iron consisted in its getting soft before fusing,
by which we could weld it together. Now, we can weld so-
dium in the sante way at ordinary temperatures. Sodium is
remarkably distinguished from potassium by the fact, that
although it decomposes water very rapidly, it does not take
fire upon the water at ordinary temperatures; but if we place
the sodium upon hot water, it then inflames the hydrogen,
which is liberated. The reason of this is, that cold water
cools the products, so that the intensity of the action is not
sufficient to enkindle the hydropen; but occasionally, when
the sodium gets to the edge of the vessel, and sticks there, the
water around gets sufficiently warmed, so as to permit in-
flammation to take place. If we by any means increase the
energy of the action, we can enable the hydrogen to take
fire, although we still preserve the same temperature. Thus,
if we place some sodium upon nitric acid, inflammation will
ensue, in consequence of the nitric acid actiug more energe-
tically upon the sodium than water. Vie can, by means of
a very beautiful experiment, determine the quantity of
hydrogen set free by a given amount of sodium.. Thus
if we take a glass tube full of water, and introduce beneath
it, in a pneumatic trough, a little sodium enclosed in paper,
the water wilt be rapidly decomposed, and the hydrogen will
ascend to the upper part of the tube, and be collected. The
flame evolved by the burning of the sodium is coloured yel-
low, from a trace of soda, and this circumstance is taken no-
tice of in the most careful analysis of substances suspected
to contain soda. The equivalent of soda is 32, (sodium 24
and oxygen 8) and this makes it a more valuable agent in
commerce than potash, because the same amount of soda pro-
duces a greater effect in the arts than that of potash. The
latter can expel soda front its combination, but soda ranks
after potash. if a little sodium is placed in some bromine,
it will combine with a slight explosion. Sodium, like potas-
sium, is distinguished by its great affinity for acids, and upon
this effect is based its various uses, as we shall afterwards
describe.

The other substances which are used in these arts are lime

and alumina. Lime exists extensively in nature as a carbo-
nate, and as a sulphate. The carbonates of lime are the
most extensively diffused bodies with which we are acquaint-
ed. It not only associates with the mineral kingdom, but it
enters largely into the skeletons of the lower classes of ani-
mals. Indeed, there is every reason to believe, that carbo-
nate of lime does not in reality form any important part of
the mineral kingdom, but that it has resulted from the suc-
cessive creations and destructions of different kinds of the

lower classes of animals, which, after forming carbonate of
lime during their life, have, after their death, given rise to
the large masses of lies, chalk, and mountain limestone,
which form so great a portion of the mountains of the globe.
In fact the more minutely we examine the carbonates of
lime the more we are driven to the conclusion that they are
aggregates of the esuvia of animals, or a collection of their
shells, which from the proximity of volcanic fires have been
melted and deprived of their pristine forms, by which they
could have been at once identified. But in addition to these
animal formations of carbonate of lime we have some of
purely mineral origin, such as calcareous spar, but these are
very unimportant in a practical point of view, as all our
lime in the arts is derived from the mountain limestone.
Sulphate of lime, or gypsum, is found' in vast quantities in
the neighbourhood of Paris, from which circumstance, in its
calcined state, it has been called the Plaster of Paris, an ar-
ticle extensively used in the casting of busts and stucco work
generally. In its pure crystalline state, sulphate of lime
constitutes the alabaster which is used in the manufacture of
those statues and works of art for which modern Italy is so
much celebrated. By the application of heat to carbonate of
lime, the carbonicacid is expelled, and lime remains behind,
in the state of a pure powder. When water is poured upon
lime, a combination takes place, accompanied by the evolu-
tion of a great heat, and slacked lime or hydrated lime is the
result. Lime consists of calcium united to oxygen; but it
is so difficult to separate these elements, that I shall do no
more than allude to the fact. If we nave a solution of lime
in water, it gets turbid when exposed to the air. This turbi-
dity is due to the formation of carbonate of lime, in conse-
quence of the affinity of lime for the carbonic acid of the at-
mosphere. Oxalic acid is remarkable for the affinity which
it possesses for lime, and they are the best tests for each
other. if we add a little of the solution of the one to the so-
lution of the other, a copious white precipitate is produced,
which is the oxalate of lime, possessing such remarkable and
peculiar qualities as to be easily recognized.
Alumina is as extensively distribuied as lime, but it is pre-
sent in a different state of combination. Alumina is met
with pure, bat lime is not, and when lime is ;rendered pure
it will not remain so long, for like .potash and soda it has a
powerful tendency to combine with carbonic acid. Pure
lime therefore does not exist in nature. Alumina has no such

affinity for carbonic acid and pure alumina, and therefore ex-
ists iii a vast variety of forms. We have it in a soft condition
somewhat similar to clay, but it is singular that the ruby,
the sapphire, and.the corundum should be composed of pure
alumina. Thus are the most extensively distributed sub-
stances in nature, on assuming the crystalline form, con-
verted into the most valuable gems, in the same remarkable
way as carbon in its pure state into the diamond. Alumina
is a perfectly white powder, and impalpable. When wetted
it forms a coherent mass, as every one is aware of. This
characterizes alumina and all its different salts. In order to
prepare pure alumina, we have recourse to a very simple pro-
cess. In the arts there exists a salt called alum : this alum
contains alumina. In ordinary alum the alumina is com-
bined with sulphuric acid, and if we take any base having a
more powmful affinity fur sulphuric acid than alumiva, we
get the alumina. For instance, if we add potash, we get
pure alumina in a white precipitate.• It is evident that this
precipitate is nut at once distinguishable from other white
precipitates, but it possesses several chemical characters. If
we take souse of it and add still more potash, the precipitate
will diSappear, but by the addition of an excess of potash it
is again made to appear. If I take,a. lithe of the solution of
alunr, and add the alkali ammonia, -the precipitate is not dis-
solved, however much I may add of it.
The other important constituent of glass and porcelain is
silica. Unlike the substances we have been describing, silica
is not a base, as we have every reason to believe it to be an
acid.' In a state of purity it forms rock crystal: Flints are
silica in great and nearly perfect purity. The sand stone of
this district is likewise silica nearly pure. In these different
forms the silica is uncombined; but in -addition to these,
silica exists in nature in numerous classes of salts. In-
deed, through the whole of the mineral kingdom we may
look upon the bases which we have described as being com-
bined with silica. Silica is the great consolidating agent.
Now I have had occasion to notice on several occasions
the general nature of a salt. A salt consists of an
acid and a base; Epsom salts consist of sulphuric acid
and magnesia, and Glauber's salts of sulphuric acid and soda.
For the purposes of the arts in which silica is extensively
employed, the sand of the neighbouring districts is found to
be sufficiently pure. In fact, when we can obtaiq sand free
from iron or carbonate of lime, we may use it in the manu-
facture of flint glass, and that of plate and crown glass. To
obtain a still purer silica weprocureiecflints,
,:lagneddo o
mift,issheo.ui(i singu-
larbe circumstance, the
theii
the hardest
substanucmne,
esstitiil
that
h
t existstt
in nproved to be like the salt in which it is found embedded, of
animal origin. In fact, although the greater variety of
marine creatures had shells of carbonate of lime, there is a
variety of them which have shells of silica, and these flints
are the aggregated skeletons and shells of the animals. In
order to oGtain a perfectly pure silica, the flints are reduced
to powder. They are first calcined, and thrown into water;
the effect of which operation is to break the flint into a
number of pieces, so that it is easily reduced to a flue white
powder, which is used in the manufacture of very fine glass
or porcelain. It is in this state perfectly white, and might
be mistaken for alumina. Silica obt6ined by this means is
not, however, chemically pure.. To obtain it'so, we make use
of a very simple process. Lmentioned that the silica is an
acid, it therefore unites with bases. Under the generality of
circumstances the combinations of silica_witlatasr.....Lare_nad...
"tiatible in water: —yr; Viiiiiever, we increase the quantity of
the base we shall get a soluble salt, and in this ready way we
may get what is called soluble glass. If we melt silica with
a large quantity of potash, we obtain a combination which
will dissolve in water. This solution was called by the older
chemists, liquor of flints, because it was the only way in
which they could obtain silica in in a state of fluidity. If we
add a little acid to it, the silica is again set free. Another
way of obtaining it is by means of fluoric acid. In this way
we get it in the form of a white light powder, as tine as can
be conceived.
To strew the great importance of these substances in the arts,
I shall point out to you the composition of some remarkable
minerals which contain them; I have already mentioned to
you one instance of the mineral felspar. It is a very com-
mon mineral, and exists in great abundance in all granites
and in syenitp, It is thought that if by the destruction of Oa