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

tions.
Potassium is lighter than water, and its colour is a pale
blue, somewhat inferior in brilliancy to silver. When cut, it
presents a very beautiful metallic appearance, but it speedily
becomes covered over with a white et ust, which is potash.—
In fact, so great is its affinity for cvgen, that we are obliged
to keep it in naptha, a substance which contains no oxygen.
When placed upon the surface of water its action is most
violent, as it decomposes the water, unites with its oxygen,
anti sets fire to its hydrogen, which burns with a vivid, violet-
coloured flame. Potassium melts when heated, and if heated
in contact with the atmosphere it burns, and is converted into
potash; but at ordinary temperatures it combines with the
oxygen of the atmospliet e without any appearance of flame.
When forty grains of potassium are converted into potash
they will absorb eight of oxygen, so that forty-eight is taken
as the equivalent of potash which unites with the different
acids. Potassium will burn with great rapidity and splen-
dour in oxygen, although it will not do so in atmosphere air,
owing to the oxygen of the atmosphere causing a crust of
potash to surround it, which defends it from further oxidation
of a sufficiently rapid nature to support combustion. The
product of its combination with oxygen we have stated to be
potash. In order to prepare potash we get the potash of com-
merce, which is combined with carbonic acid, and by dissolv-
ing it with lime and crystallizing it, we obtain the dry caus-
tic potash of the shops. Although considered as dry, yet in
strict chemical language it is not so, as it contains a quantity
of water of crystallization, which cannot be expelled. The
alkaline properties of potash are readily shown by its brown-
ing turmeric paper and turning red cabbage liquor green.
The second substance, sodium, is derived from the alkali
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 same way at ordinary temperatures. Sodium is
remarkably distinguished from potassium by the fact, that
although it decomposes water very rapidly, it dues 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 hydrogen; 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 acting more energe-
tically upo❑ the sodium than water. We 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 will 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 from 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, hut 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 lias, 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
Iliac the more we are driven to the conclusion that they are
aggregates of the exttvice of animals, or a collection of their
shells, wilich 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 front 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 nsed in the casting- of busts and stucco work
generally. In its pure crystalline state' sulphati, 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 carbonic acid 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. ime consists of calcium united to oxygen; but it
is so difficult to separate these elements, that I shall do no
inure than allude to the fact. If we have 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 fur 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 qualiti,!s as to be easily recognized.
Alumina is as extensively distributed as lime, but it is pre-
sent in a different state of combination. Alumina is met
with pure, but 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 in 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. 1 n 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 'rowel ful affinity for sulphuric acid than alumina, 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 not at once distinguishable from other white
precipitates, but it possesses several chemical characters. If
we take some of it and add still inore potash, the precipitate
will disappear, but by the addition of an excess of potash it
is again made to appear. If I take a little of the solution of
alum, 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; brit 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 obtain 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 we procure flints, and it is a singu-
lar circumstance, that the flint, which is one of the hardest
substances that exists in the mineral kingdom, should be
proved 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 obtain 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 'educed to a fine 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 obtained by this means is
not, however, chemically pure. To obtain it so, we make use
of a very simple process. I mentioned that the silica is an
acid, it therefore unites with bases. Under the generality of
circumstances the combinations of silica with bases are not
soluble in water. It', however, we increase the quantity of
the base we shall get a soluble salt, and in Ibis ready way we
may get what is called soluble glass. If we melt silica with
This solution was called by the older
hen
oft flints, because it was the only way in
aclairriiiesstss, dissolve
n liquor
vi
will y of potash, we obtain a combination which
oate'
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 floosie acid. In this way
we get it in the torus of a white light powder, as fine as can
be conceived.
To skew the great importance of these substances in the arts,
I shalt point out to you the composition of some remarkable
minerals which contain theta; 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 syenite. It is thought that if by the destruction of tha