The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1836-12-13 00:00:00

LECTURE VII.

On Wednesday evening Mr. Hemming proceeded with his
valuable and interesting course.
We have now to consider the nature and properties of the
most important of all fluids—water. Weiss was formerly sup-
posed to be an element • indeed a long period has ioe e:si- ed
since it was supposed there were only four elements, viz., earth,
air, fire, and water. We now know that these are composed of
a number of elements, water containing two, oxygen ana hydro-
gen. It was, at one time, the opinion of many eminent philoso-
phers, that there were only three elements in nature, and Van
lielmont performed a very curious experiment to prove this.
He placed a plant of willow in mould, both of which he had
accurately weighed. The root was embedded in the mould, and
the
.pot covered with lead. Tho plant was regularly watered
during the space of two years, with distilled water, at the end of
which time it was taken out of the mould, and notwithstanding
its great increase in weight the earth had only lost a few ounces.
It was thought that the additional weight arose from the de-
composition of air and water, and this led him to suppose that
these combined with earth would form every known substance
e were acquainted with. Water was first decomposed by
Cavendish, in 1776, when he succeeding in producing hydrogen
gas, so called because it ittoduces water. It was found by Mr.
Waltire that it produced water in its combustion, but not soot.
He ignited for this purpose a minute jet of it proceeding from
the philosophical candle of Dr. Priestley beneath a saucer, and
to his surprise large globules of water were formed. This ex-
periment he repeated with the seine result. It was not sup-
posed at that time that water was formed by the gas, but that
water was deposi:ed, arising from the vapour contained in the
gas and air, as it was known that every gaseous body contained
water, which, is now ascertained to be one-third part of a grain
in every.loo cubic inches of its volume. More accurate expe-
riments performed by Priestley, Cavendish, and others, led to
the Supposition that this could not be the reason, for the quantity
of water thus deposited by the combustion of a given volume of
the gasses was greater than could have been contained in them.
When Watt, the celebrated engineer saw this, he imagined that
water was formed partly by the gas, and he and Cavendish set
about igniting hydrogen and oxygen gasses in certain quantites,
Their couclusions were the same, namely; that water was formed
by the union of these two gasses by combustion. This may be
familiarly proved by holding over an ignited jet of hydrogen a
bell-shaped glass, which will in a short time be covered over by
vapour. This opinion, however, appeared to be rather unwil-
lingly received. We are indebted to Lavoisier for proving that
it is correct. Previous to his experiment, however, three French
chemists sat up for three days and three nights burning a given
quantity of hydrogen and oxygen. They found that with the
exception of a few grains the quantity of water which was pro-
duced was equal to the weight of the oxygen and hydrogen
gasses which had been burned.' But the experiment of Lavoi-
sier was much more ingenious and conclusive. He imagined
that water might be decomposed by passing its vapour over ig-
nited iron. Now, iron at a very high temperature, either at a
red or white heat, has a greater affinity fur oxygen than any
other substance in nature, potassium itself not excluded, for
potassium is sometimes obtained by heating potass with iron
filings in a retort, wheys the oxygen uniting with the iron, po-
tassium flows over. In order to decompose water by this means
a quantity of iron turnings are introduced into a gun barrel, the
centre of which is heated in a furnace. Into one end of this
gun barrel the beak of a retort containing distilled water is
inserted. Let us suppose the water to weigh nine hundred
grains. To the other end is fistened a flexible tube, which is in-
troduced beneath a receiver filled with water in the pneumatic
trough., A spirit lamp being applied to the retort, the water is
slowly vapour:zed, and the vapour passing over the ignited iron
yields its oxygen to the iron, and the hydrogen being liberated,
passes out at the extremity of the tube, and may be collected in
the receiver. When the water was all vapbnrized by this pro-
sees, Lavoisier again weighed the iron and the gas, and he
found that the hydrogen gas weighed 100 grains, and that the
iron had gained 800 grains in its oxydation, supposing 900
grains of water had been used. Another, and perhaps, more
satisfactory mode of proving the fact, and one by which
we can prove it, both analytically, and synthetically, is by
decomposing water by electric agenry. 'The Most convenient
mode of effecting this, is with a voltaic battery. In this manner
we may obtain the two gasses, either in a combined or separate
state. When we obtain them in a combined state, we can in
stantaneouslv reproduce water, by passing the elective spark
through them. To obtain them in a separate state, all we have
to do, is to fill two test tubes with water, and invert them, when,
by introducing beneath them two platinum wires from the posi-
tive and negative poles of a voltaic battery, hydrogen will be
evolved at the negative pole-, and oxygen from the positive. This
experiment Mr. Hemming satisfactorily formed, and, in our
opinion, it is one of the most beautiful of all chemical experi-
ments, and demonstrated to the audience, that the gasses were',
actually oxygen and hydrogen, by their opposite properties of
burning or supporting combustion. For the purposes of ex-1
periment, we decompose water to obtain hydrogen by means of
an oxidable metal. There are same metals which have so
poweiful an affinity for oxygen, that they will decompose water
at ordinary temperatures. This is the case with Sodium and
Potassium. Zinc and iron are usually employed for this pur-
pose; when a piece of zinc is thrown into water, an instan-
taneous decomposition' of the water will take place, in conse-
quence of the eagerness with which the oxygen of the water
unites with the zinc, and the hydrogen will be liberated, but the
action will immediately cease, because the surface of the metal
becomes covered with a coating of oxide. To remove this, an
acid is employed, which, dissolving the oxide as soon as formed,
continually presents a fresh surface to the water for oxydation,
and thus the action goes on until the whole of the zinc is
oxydated, and dissolved, or all the water is decomposed, or the
acid is expended. When hydrogen gas is mixed with atmos-
pheric air, and inflamed it produces an explosion, and more espe-
cially when mixed in the properties of one part of hydrogen to
five parts of atmospheric air. A much more powerful explo-
sion is produced when two parts of hydrogen and one part of
oxygen (the proportions in which these gasses form water) are
mixed together and inflamed. In this explosion, it is said by
some, that these gasses expand into 30 times their space, and
according to others into 15, but they as instantaneously con-
dense together to form water. The amount of explosion, how-
ever, has not been accurately determined. The sounds we
hear are produced by air striking against air. The ultimate
particles of water are impenetrably hard, for if we confine
water in a vessel from which the air has been extracted, the
water will produce a noise similar to that of a melted metal
falling. We must then believe that the particles of water are
impenetrably hard. The properties of oxygen and hydrogen,
having been explained by Mr. Hemming-, in a previous course
of lectures, delivered at the Mechanics Institution, at the com-
mencement of the present year, he did not dwell upon them,
but confined himself to a distinguishing property of each.
Oxygen is a great supporter of combustion, and of respiration.
So intense is its power of supporting combustion in its separate
state, that if we introduce a piece of ignited wood, without
flame, into it, the wood will be instantly inflamed. Hydrogen
burns with a lambent blue flame, but is not a supporter of coin-
bust ion.

Water, then, is a compound of oxygen and hydrogen, but in
all probability it has only once been procured in a perfect state
of chemical purity. Sir Humphry Davy distilled water on this
occasion in a silver vessel very carefully, and received it in ves-
sels of gold and silver. From this water, by means of voltaic
electricity, he then produced hydrogen, which was without smell.
When we decompose ordinary water the hydrogen evolved al
ways exhales a faint odour, in consequence of the foreign mat-
, ter which the water contains, and which, hydrogen gas, as
shown by. Mr. M'arsh's beautiful test for arsenic, is capable of
holding in solution. It would, however, be useless to take this
trouble. to obtain water in its pure state, as nothing can be more
insipid than water in such a state. River and spring water con-
tain atmospheric air, as well as vegetable, animal, and mineral
substances. When water contains vegetable or animal matter
it is soon decomposed, as it. is improperly called. The water is
nut decomposed, but the foreign matter which it contains, in
consequence of which a bad smell is emitted by it. Persons
who supply water to vessels for the purposes of a long voyage,
introduce it into charred casks or into iron tanks coated with
tar, try which means this spurious decomposition is prevented.
Water, when deprived of as much of these impurities as possi-
ble by double distillation, becomes very insipid, but when ex-
posed to the atmospheric air, which it absorbs very quickly,
partly regains its pleasant taste. We cannot deprive water of
all its impurities, but we can separate it from the salts it may
contain. The impurities of water, arising from the presence of
these salts, about which so much is said, are seldom prejudicial;
indeed, the snore impurities of this nature the water in general
contains, the more beneficial is it considered; fur we find the
springs at Tunbridge, Cheltenham, Harrogate, &c., to con-
tain salts which have a salutary medical effect, so that the
more impure, the more valuable the water becomes, in some
cases. The mechanical impurities are more important than
the chemical impurities; it is usual to separate these by simple
filtration. All the filters we have depend upon cue principle;
t we
constructedv‘.ish to
se
the water passes through substances exceedingly porous, but
twhhithec pores must be finer than the sand or foreign particles
poaf
porous
sFor stone. t h i s
Therepu purpose, oiss a e,
trifling fi
lt r
dairse
generally.
.advantage. attending the use of this stone, in consequence of the
tthoe restore pores
impurities choking
in many causepstheof pthoerossittor
of,
tshoethfialtteirt. is im-
possibleßut
of all the filters there is perhaps none
rcfluperior to one which any
individual may make with case aa trifling expense. Suppose
we take a lead pipe, of capacious duttiret er, and introduce into
one end of it a cork perforated with ai
above this let a layer of bruised charcoalnhuemlasereiltshmall holes,
layer of gravel, and above all a layer of fine sand; ent
ha
ent(t) thr
bending the pipe so as to allow that portion of it cont'airY
lies the various layers, to form the shorter leg, we have a' "
syphon
farmed, through which water may be obtained as much purified
as required. There is one advantage attending this filter—sif
the sand becomes choked with impurities it can be readily
cleansed by reversing the passage of the water through' if,
by making the shorter leg the longer by bending the pipe, by
which the impurities are quickly removed. We have thus,' for
a few pence, the most perfect filtering machine we ran employ.
Water is supposed to be composed of small particles, which
are hard, mond, and slippery. There is but a slight attractive
force between the particles of water, so little, indeed, that it is
said they fall and gravitate independently of each other. Thus,
supposing we allow water to descend from a high situation in a
mass,
it will not fall in a mass, but will separate unto innumera-
ble alobules. This is a fortunate circumstance; for, if the
water of a dense cloud were to fall in a solid mass, the inevita-
ble consequence would be destruction to every thing on which
it might descend. But there is an attraction between the ulti-
mate particles of water, by virtue of which they adhere together
with some slighLdegree or force. By dipping the finger into
water a slight quantity adheres to it, which collects at the point
when we withdraw it, and as soon as it has increased to a certain
size, it falls from the linger, and another drop forms in its place.
It is improper to say that particles will gravitate independently
of each other; drops may do so. Theearth's gravitating force
is in proportion to mass of matter, and as a drop is formed it
is carried to the earth. On account of this, we find that the
surface of water is horizontal and level as it is expressed, though
in point of fact the surface of water is never, mathematically
speaking, horizontal, as it partakes of the earth's curvature,
which amounts to more than many persons imagine. If we look
nveran extent of water one mile in length, at the extremity of
that distance the surface of water will be 8 inches lower than
the water near us, and at the distance of two miles tour times
fower than that, or thirty-two inches.
The most frequent impurities we find in water are compounds
of lime. Aliaost all the water we employ contains lime, which
is frequently precipitated by allowing it to remain quiet for a
short time. The bi-carbonate of lime and the sulphate of lime
are frequently found.; and, if we do not take care to cleanse our ,
boilers frequently, we shall ii id these substances adhering in a '
crystalline state to their. interiors. Mr. Hemming here exhi-

,i. Current IMPOSTS.
SALEs or THE WEEK. Prices. ThisWk this Year
---- -
100 Sea Island —d I/ —d
Stained — } 6360 342713
6120 Bowed Georgia
1980'
NI 1 '
l'Al°al);ztle
rn -a
and Tennessee 6l 10 1097 345295
2820 Nu..v Orleans r
23, 5 Pernambuco and Pa a', ba lOl 131 I 4074 122 72397
1 Aricati and Ceara lOl 115 3
200 Bahia and Maueio Bl
979 32215
Maranham
13 1 3074 I 41089
730 I Sawginned
95 11 3
Minas — —__ , _ . _ 1 • • • • I 136
Para
Demerara, Surinam, &c...... 11 14 28 1911
390 Egyptian lO5 141 • • • • 28068
Barbados lO —1! 21 484,
Peruvian 10.4 11 1 1
Bahama—
700 Laguayra
500 Common West India, &c 7l 10 1852 } 26006
Carthageria
Smyrna ' I
100 Manilla 95 105 J J
1870 Surat 3l 71 1300 85583
10 Madras 5 -- 71 .... 14008
60 Bengal 3l 51 3
18120 bales 18985 989905

LIVERPOOL CATTLE MARKET—MONDAY. Dcc. 12.
A Zood supply of Beef and Mutton, both in good demand. Beer at
an advance from last week, and thy' best quAlity sold at Ed. Beef 3d
to 6d, Mutton Ed to lid.

LONDON (;ORN EXCHANGE, FRIDAY.
The supplies of Grain and Flour still continue ny)lerate ; but many
vessels with Grain being shortly expeeted,,the buyers this week have
manifested great disinclination to purchase.—Wheat may again be. re-
ported is to' s per quarter cheaper than Monday for inost descrlptio,ts.
—Barley also is rather lower.--Beaus and Peas are unsaleable as the
duty on foreign is becoming low.—Oats have experienced a heavy
sale since Monday, and hardly maintain that day's prices.—Flour is
on varied.