The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1838-02-02 00:00:00

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LIVERPOOL MECHANICS' INSTITUTION.

LECTURES ON CUEUISTRY.

On Wednesday evening Dr. Kane delivered his seventh lec-
ture to is numerous audience.

We may effect the analysis of muriatic acid by putting in
contact with the liquid solution any substance which has a
powerful affinity for chlorine, in which case the chlorine will
be withdrawn from the acid cud the hydrogen will be set free,
the result being that the muriatic acid gas is decoin.,secl,
—one of its elements passing to the metallic body-, and
the other being liberated may be collected iu an Isolated
state. For instance if we pour-upon a small quantity of tiu
small quantity of muriatic acid, a very violent action takes
place, and we shall find upon applying a taper that hydrogen
is liberated. Now by means of this simple experiment we se-
parate muriatic acid into hydrogen and chlorine, the latter of
which combines with the zinc. The chlorine forms with' the
zinc a compound soluble in water and which can be crystalli zed.
Consequently by taking a given quantity of liquid inurtatic acid
and zinc, by weighing the chlorid,..ofzine' anti hydrogen, we shall
find the numbers in which hydeogeu and chlorine unite to form
muriatic acid. An analysis producing still more remarkable re-
sults can be made by 'beaus of ail apparatus consisting of a
flask containing a quantity of common salt, into which (the salt
having been previously melted and broken Into large lumps to
prevent the violence of the action) a quantity of dilute sulphuric
acid is introduced ; a rapid decomposition of the salt ensues and
muriatic acid being evolved is. conducted by means of a tube
into a vessel containing sulphuric acid. Being by. this means
deprived of its moisture, the dry gas is conducted into a tube
containing a quantity of the metal sodium which it passes over.
The heat of a spirit lamp being being applied to the surface of
the tube beneath the sodium, the chlorine of the muriatic acid
combines with the sodium so energetically as to produce coinbus-
tion, and hydrogen is entitled from the other end of the tube.
By this process a white powder is formed from the union of the
chlorine with the sodium which is nothing else but common
salt, (chloride of sodium). It is evident that it will only be
necessary to weigh the original substances and the products, to
arrive at the actual numbers.

It is a fact well worthy-of attention that the bodies which
which most resemble each other in their nature ate most con-
stantly aseociated 'with 'each other in nature ; thus we find
chlorine, iodine, and bromine, associated together as well as
manganese and iron. lodine is a substance of intense interest, as
its discovery shews the great importance of observing with ac-
curacy all the phenomena whicri occur in the arts, even in the
progress of abstract science. lodine was nut discovered by any
chemist, but by a manufacturer, and under the circumstances
in which it is formed, it could only be discovered by-a manu-
facturer. It exists only in nature iu soda alkalieS, and even iu
these in very minute quantities. It is one of those substances
which diffused originally through an immense mass of water is
by the means in which this water is used in the arts gradually
concentrated into the shape in which it is obtained. M. Cour-
tois observing that the iron pans iu which he boiled up his kelp
for the purpose of soap-making was corroded to a great exteut
by a substance which he could not find accounted for or described.
in any work un chemistry, took some of the substance to Guy
Lustre who decided it to be a new substance. We owe the ge-
neral illustrations of the priuciples of lodine to Gay Lusac, as
well as to Sim Humphrey Davy, but we must not forget that the
discovery of lodine was made by Courtois the soap manufac-
turer, of Paris, and that it could not have been discovered but in
the operations of such a manufactory as that which he con-
ducted. 'l' he generality of sea water contains iodine, as it also
does a great:quantity of chloride of sodium or common salt.
lodine exists in sea water under the form of ioaide of magnesia,
but its quantity is so exceedingly minute that it would be im-
possible by ordinary analysis to detect iodine without having
'first concentrated the sea water to an extraordinary extent.
This concentration is carried on to a great extent by the aquatic
plants which exist in the water, and when the plants are col-
lected and burnt to ashes' we find they give to us the salts
which previously existed in water, partly pure and partly
decomposed, which we use in the arts and commerce.—
The production of the iodine may be simply illustrated.. We
shall, not, however, have recourse to the complex method of
obtaining it as hi the arts, but will suppose that from the mass
of kelp the real iodine constituent has been eliminated, and that
we have only to decompose this substance to set the iodine free.
If we pour into a retort liven some iodide of potassium, a quan-
tity of sulphuric acid, and apply heat, we get a very interesting
action. Altera short time a substance will distil over into a re-
tort which condenses in a solid state. The reaction which takes
place is simple. One equivalent of the oxygen of the sulphuric
acid unites with the potassium to form potash, and both sul-
phurous acid and iodine is set free. The iodine of magnesia is
used in commerce, in order to produce the iodine. The purple
colour of the substance, procured it the name of iodine, from
the Greek. When iodine is heated it at first melts, and after-•
wards is converted into vapour. By a reduction of the temper-
ature the iodine again solidifies, and is deposited in octahedral
crystals. lodine is remarkable as being the only one of the
non-metallic bodies possessing a metallic lustre. It is sparingly
soluble in water which it colours a pale brown. It is much Inure
soluble in spirits of wine, and the tincture of iodine is a most •
important medicinal agent. One of the must important uses of it •
is, iu cases of glandular swelling in the neck, to which the in-
habitants of some parts of Derbyshire anti the neighbourhood
of the Alps are subject. Burnt sponge was fouud to be an ex-
cellent remedy in these cases; and after the discovery of iodine
it occurred to the medical men at Geneva, that sponge being a
sea plant might contain iodine. This being found to be the
fact, led to the employment of iodine in these cases, for which
sponge was considered a specific, and we now count iodine
amongst our most valuable medicines. It is a substance most
easily recognised. It has a remarkable action un starch, with
which it forms a purplish blue compuuud, called iodide of
starch. An ext ellent sympathetic iuk for secret correspond-
ence may thus he formed. Thus, if certain characters be traced
with a solution at starch on paper, when dry, the characters will
be invisible, but upon brushing them over with a solution of
iodine, they immediately show themselves of a blue colour. By
employing a weak alkali the writing again becomes
iu const•queuce of the iodine leaving the starch to combine with
the alkali, but by neutralizing the alkali whir an acid the iodine
will again unite with the starch, and the writing will reappear.
if we allow a little of the blue iodide of starch to boil over a
spirit lamp, the colour will risappear, but upon the cooling of
the compound it will again reappear, though not so deep a
colour. The rationale of this is yet a mystery, but is supposed
to be owing to some species of decomposition. -lodine -enters
into a number of combinatiuns with the metals, but it does not
unite with them so powerfully as chlorine, and, consequently,
we cannot under ordinary circumstances obtain the ,combina-
lions, except by indirect methods. It' we take a solution of
corrosive sublimate, and add to it a solution of iodide of potas-
sium, we obtain a red precipitate of au exceedingly brilliaut
line, indeed, it is one of the most beautiful reds which we know
of for surpassing vermillion. This substance is a combination
of iodine with quicksilver, caned iodide of mercury. ln
making this experiment it is requisite to be cautious in adding
the iodide of potassium, for, if it he used in excess,
the purple
again disappears, being immediately re-dissolved. When the
iodide of potassium is added to a solution of lead. a precipitate
is formed of a rich canary 'colour. The iodide of mercury and
th, iodide of lead are excellent. tests for iodine in aesrtate ti
combination, and starch is an excellent test for it where it
free. If we mix a little of the iodide of potassium with starch
there will be no chang,e of colour, because the iuditts has a
weaker affinity for the starch than it has for the potassium; lint
if a stnallquantity of au acid be added, the alkali unites with
in, leaving the iodine free to unite with the starch, which it
does, and produces the blue colour. By these means we are
enabled to prove the presence of iodine without the possibility
of a shadow of doubt lodine unites with nitrogen, uild
comes highly explosive. The iodide of nitrogen is a brown
powder, sod if it be struck slightly with a stick, it detonates
with a loud noise. . .

Bromine is generally associated with iodine, but it exists in
still smaller quantities. It was discovered by Balard, the cele-
brated manufacturing chemist of Montpelier. It is remarkable
as occupying au intermediate position uetween iodine and chlo-
rine. We have seek., that chlorine is gaseous, and that iodine
is solid. Now Bromine is a deep red liquid. Not only in its
liquid state, but in every other property, does bromine stand
exactly half way between chlorine and iodine. The odour of
bromine is far worse than that of chlorine, from which circum-
stance it has derived its name. Biondue evaporates so fast,
that it cannot be kept in the liquid state, unless the bottles in
which it is contained are immersed in water. The instant a
drop of bromine falls upon potassium, an energetic combination
takes place, accompanied by flame and a loud explosion. In-
deed this substance ranks only interior to chlorine in its com-
bination with the metals. . _ .

A substance which possesses some interest in a scientific point
of view, but which has not yet proved of such practical import-
ance, is fluorine. There has long been known in this country
a mineral called fluor or Derbyshire spar. It consists of lime
combined with a peculiar acid. After Sir Humphrey Davy
had suggested the theory now generally adopted respecting the
nature of chlorine, he proposed to admit fluorine as a separate
element. Float eof lime is easily decomposed. This is done by
pouring sulphuric acid into a vessel coutaining powdered 'loath
of lime. The sulphuric acid unites with the lime, and fluorine is
expelled, but as fluorine unites with the silicon of glass vessels,
turning out the oxygen, it is impossible to collect it pure by such
means; but the Rev. Mr. Knox of Dublin, has succeeded is
obtaining it pure in vessels of fluor spar constiucted in a pecu-
liar manner. All he has been able, however, to determine re-
specting it is, that it is gaseous and colourless. Indeed we, as
vet, know very little more about its properties or combination,
except the fluoride or hydrogen and its actioulupou glass. - -
One of the most extensively distrinuteitsUbstances in nature
is that of which sand, quartz rock, and lock crystal, are com-
posed. These locks, as well as the flints, !build in such abund-
ance in some parts of the country, are found to consist of a sub-
stance which has recently been discovered to be au acid, called
silica, or silicon, combined with oxygen. Silica consims of our-
half its weight of oxygen united to the base, and possesses very
powerful affinity fur alkalies or bases. When silica has once
been formed, it is insoluble in water, and the way, therefore, in
which we form its combinations is, by welting silica with its
bases. Common clay is one of the most remarkable of the sill-
cates,—:it is a combination of silica with alumina or pure clay.
By combining silica with au alkali and inciting it with an in-
tense heat we obtain glass. The glass indite at Prague stands
heat much better than that made in this country, being a double
silicate of potash and lime. Tbe glass made in England con-
tains iron or lead and is melted at a low heat. The lead is used
to give the glass a lustrous appearance as well as to enable the
workmen to cut it more easily. By means of !Woric acid we
may etch engravings on glass, indeed some attempts were made
to take impressions from it as front a copperplate, but tile glass
was. so liable to be broken that the thing was abandoued.

• Phosphorus is a substance almost peculiar to the animal
kingdom. There are not in nature more than half a dozen
minerals containing phosphorus, and therefore lye must look
upon it as being an /went of the animal kingdom. We meet
with phosphorus in different parts of the animal econ,nny, es-
ii) two, namely, the softest and the
,hardest of all the
tissues. We find it iu the brain as well as iu the buttes. But
although all the brain contains it, the outside of the brain eon.
tains it in the greater abundance, and some natural philosophers
consider that the energy of the mind depends upon the amount
of pbusphorus which this portion of the (train contains. In or-
del to obtain phosphorus a simple process is necessary, we have
recourse to the bones in which phosphorus is couthined with oxy-
zen in the form of phosphoric acid. There are in nature two ex-
tensivo tribes of animals, which are characterised by the
organization of their skeletons. One of these classes have the
skeleton in the inside and the other has them on the outside.
Those animals, such as the crab, lobster, etc., which- base their
skeletons on the outside, have no phosphorus, but it exists in
those which have internal skeletons. If we take a bone and
burn it, there remains a whitish substance which is phosphoric
acid united with lime. If we add to this phosphate of lime some
sulphuric acid. a great quantity of phosphoric acid is set free,
this being tal;xed with ellareoat and healed, phosphorus distils
over. Care must he taken in making this experiment. as there
is considerable danger, shun.d the retort bleak. Phosphorus
unites with oxygen iu several ploportiens. When it is burned
with a brilliant flame in atmospheric air, there is turned I.llos-
plunk acid. If, however, we iimit the supply of oxygen, and
provide an excess of phosphorus, we shall tied our acid to lie
formed containing less oxygen. The reimposition of oxide of
Phosphorus is not perfectly known, becatise it is wait:tilt to get
it free from excess of phosphorus. If some phosphorus lie placed
at the bottom of a glass containing hot wajW, it will melt, and
if a stream of oxygen be urged upon it wh tit remains at the
bottom of the vessel, by means of a finetube, it will inflame
with considerable energy of combustion. A brick•red powder