8 
$ f but a few ashes ; ami the 25 grains of 
'ciiarcoal had totally disappeared. 
The gases disengaged were found to v eigii 
d together 113.7 grains: and there were found 
two different kinds of gas, viz. 144 cubic 
inches of carbonic acid gas (211), weighing 
100 grains; and 380 cubic inches of a very 
light gas, weighing 13.7 grains. 1 his last gas 
took lire on being applied to alighted body 
in contact with the air. In examining after- 
wards the weight of the water which had 
passed into the flask, it was found less than 
that in the retort A by 85.7 grains. 
In this experiment, there tore, 85./ grams 
of water, and 28 grains of charcoal, formed 
carbonic acid gas equal to 100 grains ; and a 
peculiar gas susceptible ot inflammation, 
equal to 13.7 grains. . , 
Exp. 3. The apparatus being arranged as 
above, instead of the 28 grains ot chaicoal, 
274 grains of thin shavings of iron, i oiled 
up in a spiral form, were introduced into the 
tube E E : the tube was then brought to a 
red heat as before ; and iu the same manner 
the whole of the water in the retort A was 
made to evaporate. Iu tins experiment 
there was disengaged only one kind ot gas 
which was inflammable : there was obtained 
of it about 406 cubic inches-, weighing 15 
•rains ; and the 274 grains of iron, put into 
Jie tube E F, were found to weigh 85 grains 
above what they did when introduced ; and 
the water first employed was diminished 100. 
The volume of these iron shavings was 
found to be greatly enlarged. '1 lie iron was 
scarcely any longer susceptible ot attraction 
by the magnet; it dissolved without, effer- 
vescence in acids : in a word, it was in the 
state of a black oxide, like that which has 
been burnt in oxygen gas. In this experi- 
ment there was a real oxidation of the iron by 
the water, entirely similar to that effected in 
the air by the aid of heat : 100 grains of water 
were decomposed; and ot these 100 grains 
85 united to the iron, to reduce it to toe 
state of black oxide : these 85 grains, there- 
fore, were oxygen ; flie remaining 15 grains, 
combined with caloric, formed an inflamma- 
ble gas. It thence follows that water is com- 
posed of oxygen and the base of inflamma- 
ble gas, in the proportion of 85 to 15, or of 
17 to 3. Water therefore, besides oxygen, 
which is one ot its principles, and which is 
common to it with a great many othei sub- 
stances, contains another peculiar to itself, 
and which is its constituent radical. This 
radical has been called hydrogen, that is to 
say, the generator of venter ; and the com- 
bination of this radical with caloric, is dis- 
tinguished by the name of hydrogen gas. 
See Air, page 31. 
This radical then is a new combustible 
body ; that is, a body which has so much 
affinity for oxygen as to be able to take 
it from caloric, and to decompose oxygen 
gas. 'Iliis combustible body itself lias 
so great an affinity tor caloric, that unless 
engaged in some combination, it is always in 
the aeriform or gaseous state, at the degree 
of pressure and temperature in which we 
live. 
It' it is true, as has been shewn, that water 
is composed of hyorogeh, combined with ox- 
ygen, it thence results, that by re-uniting 
these principles, water ought to be re-formed. 
This indeed is what takes place, as will be 
seen by the following experiment : 
CHEMISTRY. 
Exp. 4. lake a wide-mouthed glass bal- 
loon, A (tig. 19), capable of containing about 
four gallons, and cement touts mouth a small 
plate of copper BC, having above it a cylin- 
der of the same metal, D, pierced with 
three holes to receive three tubes. 1 he hist 
of these, h H, is destined to be connected at 
its extremity h, with* an air-pump, m order 
that the balloon A may be exhausted ot air. 
The second tube, gg, communicates by it. 
extremity M M, with a reservoir of oxygen 
gas, and' is destined to convey it mto the 
balloon A. The third tube, D d, communi- 
cates bv the extremity N N, with a reser- 
voir of hydrogen gas : the extremity ot this 
tube terminates in an aperture so small as 
scarcely to admit a very delicate needle. It 
is through this aperture that the hydrogen 
gas contained in the reservoir is to pass into 
the balloon x\. In the next place, the small 
plate BC is pierced with a fourth hole, into 
which is inserted with cement a glass tube, 
through which passes a wire r L, having a 
its extremity L, a small ball destined to make 
an electric spark pass between the ball and 
the 'extremity y, of the tube that conveys the 
hydrogen gas into the balloon A. i ie wue 
I'L is moveable in the glass tube, in ordei 
that the metallic ball L may be brought 
nearer to, or removed from, the point v ; the 
three other tubes CH ,gg, hi h, Da, me 
each furnished with a cock. ' . 
That the gases may be conveyed m a 
very dry state through the tubes which con- 
duct them into the balloon A, and that they 
may be deprived of w r ater as much as possi- 
ble, vou must put into the swelled parts M IV 
and N N of the tubes, some salts capable ot 
attracting the moisture with great activity, 
such as acetite of potash, muriate of lime, or 
nitrate of lime. These salts should be only 
coarselv pounded, in order - that they may 
not form a mass, and that the gases may pass 
freely into the interstices lett between die 
fragments. You must be provided with a 
sufficient quantity of very pure oxygen gas, 
and nearly a triple volume of hydrogen gas, 
equally pure. To obtain it in this state, and 
free from ail mixture, you must extract it 
from water, decomposed by means ol very 
pure and ductile iron. 
When every thing has been thus prepared, 
adapt to the air-pump the tube h II, and ex- 
haust tlie air in the large balloon A ; then 
till it with oxygen gas, by means of the tube 
a- a- ; an d by' a certain degree of pressure, 
force the hydrogen gas to pass into the bal- 
loon A, through the extremity y of the tube 
dDy ; then kindle this gas by means of an 
electric spark, and it you renew the quantity 
of each of these two gases, the combustion 
may be continued for a long time. 
In proportion as the combustion pioceeds, 
water is deposited on the internal suituce of 
the balloon A : the quantity of this water 
rrraduaUv increases, and it unites itself into 
farge drops, which run down the sides ot the 
vessel, and are collected in the bottom of it. 
It was by aft experiment of this kind that 
Lavoisier ascertained that 85 parts, by 
weight, of oxygen, and 15 parts, also by- 
weight, of hydrogen, are required to com- 
pose an hundred parts of water. 
Hence it is evident that water is not a 
simple substance ; that it is composed of two 
principles, oxygen and hydrogen ; and t.iai 
, its two principle* separated from each other. 
S3 1 
have so great an affinity for caloric, that at 
the common degree of temperature ana 
pressure they cannot exist but m.Y. 
gaseous form. , 
Chemical operations and instruments. 
The reduction of solids into powoers o, dil- 
ferent degrees of fineness, by means ot pul- 
verization, Ac. is a necessary preliminary 
operation previously to their being cne- 
mically acted upon. But these processes can 
never reduce substances into their pvuriaiy 
or elementary particles: they do not even 
destroy the aggregation of bodies; fei eveiy 
particle, after the most accurate trituration, 
forms a small whole, resembling the oi iginal 
mass from which it was divided. 1 he real 
chemical operations, on the contrary, such 
as solution, destroy the aggregation ol bodies, 
and separate their constituent and mtegiant 
particles from each other. Brittle substances 
are reduced to powder by' means oi hammers, 
pestles and mortars, stones, and muueis. 
Pestles and mortars are made either of metal, 
;lass, porcelain, marble, agate, Ac. becom- 
ing to the hardness and properties of the bo- 
dies to be pounded. Wedgewood’s ware af- 
fords a most excellent kind of mortar foi most, 
purposes, as it is very strong, and not liable 
to be acted upon by acids. Many bodies 
cannot be reduced to powder by the foregoing 
methods : such are fibrous substances, as 
wood, horns of animals, elastic gum, and me- 
tals which flatten under the hammer ; tor 
these, files, rasps, knives, and graters, aie ne- 
cessary. 
The separation of the finer parts of bodies 
from the coarser, which may want lai ther pul- 
verization, is performed by means of sitting ol* 
washing. 
A sieve for sifting, generally consists ot a 
cylindrical band ot thin wood, or n.rttai, 
having silk, leather, hair, wire, Ac. stretched 
across it. Sieves are of different degrees of 
fineness; 
H ashing is used for procuring powders oi 
an uniform fineness much more accurately 
than by means of the sieve ; but it can only 
be used for such substances as are not ac ted 
upon by* the fluid which is used. 1 he pow- 
dered substance is mixed with water, or some 
other convenient fluid: the liquor is allowed 
to settle for a few moments, and is then de- 
canted oli : the coarsest powder remains at 
the bottom of the vessel, and the finer passes 
over with the liquor. By repeated decanta- 
tions in tiiis manner, various sediments are 
obtained, of different degrees ot fineness ; 
the last, or that which remains longest 
suspended in the liquor, being the finest. 
Filtration is a finer species of sitting. It is 
sifting through the pores of paper, or flannel, 
or fine linen or sand, or pounded glass, or 
porous stones, and the like ; but is used only 
for separating fluids from solids, or gross par- 
ticles that may happen to be suspended in 
them, and not chemically combined with the 
fluids-. Tliqs salt-water cannot be deprived of 
its salt by filtration; but muddy water will de- 
posit its mud. No solid, even in the form of 
powder, will pass through the above-mentioned 
liltring substances: hence if water or other 
fluid, containing sand, insects, mud, Ac. is 
placed iu a bag or hollow vessel, made of any 
of those substances, the sand, Ac. will re- 
main on the illtre, and the liquor will pass 
through, and may be received clear in a ves- 
sel under it Unsized paper is a very con- 
