The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1836-12-06 00:00:00

A POPULAR COURSE OF CHEMISTRY.
MECHANICS' INSTITUTION.
lA:cruets Vi. •
On Saturday eveniros, Mr. Hemming proceeded with his
valuable lectures to'a crewded audience.
The subject fur ern sideration in the following lecture is the
new and improved modes for supplying and continuing the sup-
ply of light. Prima time immemorial until within a very re-
cent period, the contrivances for a supply of artificial light were
very few, anti almost entirely confined to the combustion of
animal, vegetable, and mineral oils. The animal and vegetable
oils are well known : by mineral oil is meant that bituminous
fluid which is obtained in such abundance in Persia, called
naptha, or petroleum, as to allow of its being used for culinary,
and tither domestic purposes. Until very recently, these sub-
stances were all decomposed by combustion in lamps of a very
similar kind; for before the introduction of the candle, tallow,
was, and fat, as well as oil, were burned in a lamp. The lamp
contained a mass of fibrous matter, commonly called a wick.
The wick was not always combustible and 'destructible, for in
some cases, amianthus and asbestos were employed. The wicks
consisted,- as already stated, .of.a fibrous material, and con-
tamed a great number of pores, up which, by virtue of capillary
action, the oil, &c. would rise above the ordinary surface of the
fluid in the vessel, to feed 'the wick. When in this state, an
ignited body is applied to the wick, it meets with the wax, tal-
low, or oil, in a very minute state of divieion • and, by decom-
posing them iota tlieir elements, as we must always do to effect
ignition, we produce a light. In almost all these cases, the
quantity of light wo produce, depends, almost entirely, upon
the quantity of carbon we burn; and not upon the quantity of
carbon or charcoal the substance may contain. The greater the
quantity of carbon which enters into combination with the oxy-
gen of the atmosphere at a high temperature, the whiter and
more intense will be the quality of the light. Indeed, we may-
take it as an axiom, that tho quantity of light produced by burn-
ing these substances, is in proportion to the quantity of carbonic
acid formed. We must, therefore, have a due supply of atmos-
pheric air, or oxygen, to enter into combination with this car-
bonaceous matter, to form carbonic acid gas. 'rho principal
elements we find in these substances, are combinations of car-
bon and hydrogen ; which are the principal components of all
matter which burns with light and heat. Hydrogen will burn
with a faint flame, scarcely visible by day, when uncombined
with carbon; but when hydrogen contains carbon united with
it chemically, and we burn thm in intimate connexion with
oxygen, we produce intense energy of combustion, and a beau-
tiful white flame. Now although the quantity of light depends
upon the quantity of solid matter contained in the substances
we burn, yet more depends upon our mode or manner of
burning them. Thus, if a eurrent of hydrogen gas be directed
upon a piece of lime, and ignited, the lime will be dissipated in
minute particles of intense whiteness. Charcoal,- burned in
oxygen gas, throws off similar particles, and affords a brilliant
light; but, when charcoal is burned under ordinary circumstan-
ces, it merely of a dell red ligbf. If, however, a stream
of atmospheric air be urged upon the ignited charcoal, its light
will be much increased : a white light is more intense than a
red one; and a white heat than a red one; and it 'may he con-
sidered an axiom, that the intensity of light and heat, is in
proportion to the whiteness of the substance in combustion. In
older to increase the heat of oil, tallow, &c. in combustion, we
must force through them a great deal of atmospheric air. In the
old lamp, this was impossible ; and the invariable consequence
wag, that the combustion was not. perfect, and that a dense
red flame, with a giAlt quantity of smoke was the result. In
this case besides losing a quantity of light, the smoke, which
is the most valuable portion of the material, likewise eseape,
merely on account of a deficient supply of atmospheric air, as
the air could only play around the external portion the flame. It
occurred to Monsieur Argent!, of Geneva, that if be could force
a quantity of air through the flame he could effect a more per,
fect combustion of the oil. This may be proved by a very sim-
ple experiment. If wc take time bicarburetted hydrogen or (defier: t
gas, which is the must valuable illuminating gas we possess, and
ignite it as it comes out of a tube without a burner, the light will
be mm h inferior to what it would give if it issued from a gas-
burner through whieli a current of air passed. Notwithstand-
ing this it will afford a brilliant light, much superior to oil or
coal gas. This light arises from the union of the carbon con-
tained in it with the oxygen of the atmosphere, for if we burn this
gas in an atmosphere which will not unite with the carbon, there
will be very little light, and a great quantity of smoke or carbon.
Mr. Hemming then mixed some of this gas'with chlorine, which,
though a supporter of combustion, will not unite with carbon,
when the effect he described ensued. M. Areand imagined
that if he passed a current of air through the centre of the
burner and of the wick he should produce a whiter light by the
more complete combustion of the carbon. He therefore con-
structed a lamp with a circular burner. through the centre of
which the atmospheric air being ratified by the beat passed
with some degree of force. Still, however, this lamp slid not
altogether realize his expectations, for the flame was somewhat
red, and there was a portion of smoke evolved from it. But it
happened by accident that his brother inverted a glass tube
over it while the lamp was on the chimney-piece, when a perfect
combustion of the carbonaceous mattter was effected, and this
showed him that what we call it chimney was, in fact, a chim-
ney because it caused a draught around the flame. These lamps
were shortly after introduced all over Europe, and have super-
seded every other description of lamp. It than became neces-
sary to ssoct rid of the shadow of the lamp. Those which are
now used on the drawing-room table contain the oil in a rim
round the burner, and hence cast a circular shadow. The foun-
tain lamp was then constructed, but owing to to the inconve-
niences attending its use it never became generally patronized.
A very curious lamp was afterwards constructed in France, in
which the oil was forced a considerable height to supply the
wick by means of a couple of small pumps, worked by clock
machinery placed underneath the lamp. One great peCuliarity
attending this lamp, which casts no shadow, is, that however
high the wick is raised above the metal surrounding it, the flame
has no tendency to descend, in consequence of the free supply
of oil which it receives from the pumps. The glass chimney is
also capable of being raised or lowered at pleasure. It was
early discovered 'that if the lower part of the chimney was
flanged the lamp would burn better. Few persons know thews
of this flange. Its upper portion should be exactly opposite the ig-
nited portion of the wick, for if it is situated higher or lower the
flame will be less. The reason is, that by means of the flange
the air is thrown upon the ignited portion of tbe wick. We find,
inansiny lamps the flange to be of acertaris height, and that the
galleries are constructed of a similar height to contain the chim-
neys. There is a great advantage in having the metal at a
great distance from the light because the metal-getting hot car-
ries off the heat necessary for the perfect decomposition of the
carbonaceous matter. The advantage of not allowing the heat
to he thus carried off is illustrated by the tar lamp of Mr. Beale,
an economical and valuable contrivance for burning tar after the
naptha has been distilled from it. It was found, Mr. B. said, that
the rim must be as thin as possible; if thick, so great( would be
the quantity of heat abstracted that the tar was not conseimed as it
would otherwise lie. The Naptha lamp is a very valuable con-
tsivance if Properly managed, and is much cheaper than a gas
light would be. The Naptha is a distillation from coal tar,
and requires to be burned with a fine wick, which must not- be
more than 1-50 of an inch above the surrounding metal. It
burns with a dense smoky flame until a glass is produced over
it, when it emits a brilliant white light. The great improve-
ment of modern times is oil anti coal gas; these, however, being
so well known, and Mr. Hemming having entered so fully into
the subject on his last visit to Liverpool, he merely glanced at
thein en passant. An improvement has been made on the safety
lamp of Sir H. Davy by Mr. Roberts, of London. This con-
sists in encircling the wire gauze of his lamp with a glass
cylinder, and causing the air admitted for the consumption of
the lamp to pass through the flame by means of a cone, where-
by all danger is removed. Mr. "lemming considered the
Davy lamp, if properly managed, to be perfectly safe, even in a
blower; tint, certainly, were there any danger in a blower with
Sir H. Davy's lamp, that danger must be removed by the use of
Mr. Roberts's contrivances.
We have now to consider a few other improvements in the
mode of producing artificial light; 'amongst these are to be
noticed the improvements which have recently been made in
the manufacture of candles awl candlesticks. There was one
which the lecturer wished to shave produced could he have
procured it in any 'of the London shops. It was a patent
candlestick, by which the candle was made to burn in an in--
dined position, so. that there was no necessity to snuff the wick.
The reason why a candle requires snuffing is, because the car-
bon at the top of the wick is enclosed by the flame so as to pre-
vent the access of the oxy,gen of the air remove it. Un-
fortunately, however, for the invention, while this beneficial
effect takes place another evil is produced, arising from the
dropping of the tallow. Like many other patents, this has
been productive of very little advantage to the patentee. There
is, however, another invention which renders the snuffing of
the candle unnecessary. It is a wick twisted in two spiral di-
rections, which, as it becomes ignited, untwists and turns in
the opposite direction, and insensibly smoulders away. These
are what are called candles with metallic wicks. At first, oxide
of hiseriuth was applied to the wicks; but this is not necessary,
neither is it any longer used. A great improvement has been
made in tallow and oils within a short period; indeed, until very
lately, very little attention was paid by chemists to this sub-
ject. It was not thonght that they could decompose these sub-
stances into their proximate elements. A little attention has,
however, proved that they are easily divisible into two cult'
stances—the one fluid, called elaine, and the other solid, called
stearine. The stearine of cocoa-nut oil has been accordingly
used in making candles, which' are little inferior to wax.
spring which we find employed to keep the candle aton uniform
height in the improved candlestick is by no means a new .
inven-
tion, as it has been applied to carriage lamps fora long period.
After the last lecture upon instantaneous lights,
institution
Hem-
ming said he had been presented by
with a bundle of josticks, which werealunseeindbe'in
matches. Accompanying the presentofcthruainsesi
slow
al description of the
njgcsbirsltohree
in overt room in China,
gaor(tii,caleudisthaepjpelitekdkbiys
atwhcaeas Cmhillienebsuer.
(nheisntensewwheicrhd tfhoris
the image of their god, which is kept
and in every vessel, from the largest war stunwkattoerthelstmiaslflerest
boat. To last the longer, it is dipped o
itris to the Chinese we are indebted
These josticks are burning near
of our
.houses. It used to be the
fluently perfumed; indeeedr.s
for the idea of our pantiles.
what is called the scrap
Canton at to practiceover_
turn happen to meet with, turn the josticks theywhich caused
of our young European residents
The jostick was also used
for
n 0 small f
lighting cigars.
the
of lime.
thepuhrupbobseub natives.oamong
We have now only two other cases of artificial light. The
d is caused by burning
flit
onus tr
rbeeuatuotfi faual
yo_fhayldl ,rao
gn de
ut hgeams
to,
ps to sup lue np
pees
This light
is commonly called the Drummond light, but erroneonsly
as it was not invented by him. It is most extensively employed
in microscopes, instead of the solar light. Professor Daniel's
safety tube is the one most commonly employed, in which the
two gasses meet near the orifice. Mr. Hemming bad invented
a safety tube by which tbe two gasses might be used in a mixed
state without danger, but a strong prejudice existed aginst it.
Mr. Hemming then exhibited the light produced by these
gasses when burning on lime, which afforded general satisfac-
tion. Mr. Beak's tar lamp is a very useful invention's it con-
sists of an argand receiver to hold time tar. In order to ignite
the tar, which requires no wick, we must introduce some sub-
stance which will take fire at a low temperature, such as tur-
pentine, and set fume to it. This will ignite the tar, which will
burn with a very dull red flame; when it is pretty well ignited,
a double cone is placed over it, which supplies the lamp
.with
continual succession of heated air. A corrent of air is then
forced through the middle of the flame, up a small tube the I-10th
or the 1-13th of an inch in diameter. Under ordinary circum-
stances, the excess of carbon contained in the tar is-evolved;
hut, if we blow through the centre of this ignited tar, a portion
of the carbon which would otherwise escapo as free carbon will
enter into combination with the oxygen and form a very beauti-
ful white light. These lamps can only be used where there
is a moving power on the premises; nevertheless, Mr. Hem-
ming hsd seen, in London, a shop lighted up with an apparatus
of the kind. To supply the rersnisite blast, the shopkeeper
had inverted one butt within another coutainine. waters the air
contained in which supplied two of these lamps for. twenty
minutes. There is a slight noise made by the blast infpatsasriinel
through the flame. Hoc ever, for lighthouses or
hmatneuseac_amps
there is nothing which bears a comparison
_Tit ha..nnl,
and
for economy or beauty, for the tar is sold at 6d. prwgi l" give
when the tar is dilly burned one of these
per hour.
as
calculation, whilst it only.costs ;Id. _ Hemming much light as 4I argand burners, according to Faraday's
In the lecture Or to-morrow evening, Mr. .
treat ripen the
.neture and
show its chemical compositiou, its impurities, and the mecha-
proper.ties. of water, in which he will
nical and che•iical reed° of detecting and separating these
impurities