208 CHEMISTRY. 
way, it is obtained cryftallized. By parting red-liot iron, refervoir of oxygen gas, from which the balloon is to be 
or even bricks, under jars filled with water, the water filled. The third tube a T)d, "communicates by its ex- 
will become decompofed. tremity */N, with a refervoir of hydrogen gas. The ex- 
The following is a very fimple' experiment: Take a tremity d of this tube terminates in a capillary opening, 
gun-barrel and place it in a furnace, as fhewn in the through which the hydrogen gas contained in the refer- 
Chemiftry Plate II. Jig. n; to its raifed end adjuft a voir is forced, with a moderate degree of quicknefs, by 
funnel to contain the water, and to let it out only in the preflure of a column of one or two inches of water. 
drops by means of a cock; inliead of a large funnel, a 
tube bent fyphon-faffiion, with a fmali funnel at the end, 
may be ufed. At the other end of the gun-barrel place 
a tubulated receiver, or a two-necked bottle, to catch the 
water which runs out without being deconipoied ; to one 
of the openings adapt the pneumatic chemical apparatus; 
then make the gnn-barrel red-hot, and let in the water 
drop by drop : hydrogen gas will be the refult. 
2. At the Royal Inftitute in London, on the 28th of May 
j8oo, Dr. Garnett, in his LeCture on the Compofition 
and Decompofition of Water, made a curious experi¬ 
ment, on which we cannot /refleCt without thinking that 
it may lead to feme important enquiries, and may throw 
light on feVeral phenomena of the animal economy. 
Decompofition of Water by the Galvanic Influence .—A num¬ 
ber of pieces of zink, each of the fize of a half-crown, 
were prepared, and an equal number of pieces of card 
; cut in the fame form : a piece of zink was then laid up¬ 
on the table, and upon it a half-crown ; upon this was 
placed a piece of card moiftened with water; upon the 
card was laid another piece of zink, upon that another 
half-crown, then a wet card, and fo alternately till more 
than forty pieces of each had been placed upon each 
other; a perfon then having his hands well wetted, 
touched the piece of zink at the bottom with one hand, 
and the half-crown at the top with the other; he felt a 
ftrong fhock, which was repeated as often as the contaCf 
was renewed. See the article Galvanism. Whenthe 
pieces were touched with pieces of metal held in the 
hand, the effect was the fame, or rather more ftrong; but 
when fealing-wax, glafs, or any other non-conduftor, 
was ufed, no fhock was perceived. This apparatus feems 
to form an artificial torpedo. A glafs tube being filled 
with water, and corked at each end, and a copper-wire 
forced through each cork, fo that the ends of the wires 
were about three inches diftant from each other in the 
water, the other extremities of the wires were made to 
communicate, the one with the bottom piece of zink, 
and the other with the top piece of filver; bubbles of 
hydrogen gas immediately role from one of the points of 
the wire within the water, which moved upwards in a 
continued ftream, and united at the top of the tube, 
while the other point of the wire was quickly oxydated, 
the oxyd falling down rapidly to the bottom of the tube. 
M. M. Van Trotzwick and Deiman have difeovered 
that water is decompofed by the pafl'age of the eleChic 
fpark; and that it is feparated into two elaitic fluids, 
which inflame and recompofe water, when this fpark is 
excited in them. This beautiful experiment affords a 
fuliicient anfwer to the greater part of the objections 
which have been made to the decompolition of this 
fubftance. 
Recomposition of Water. —It is not fufficient to 
have decompofed water into its conftituent principles 
oxygen and hydrogen; hut it is alfo necelfary, with a 
view to bring full conviction of its being a compound 
body, even to reform the water with the elements which 
have been produced from its decompofition: modem 
chemiftry enables us to accomplifh this very curious 
operation. The apparatus which was cofltrived for this 
purpofe by M. Lavoilier, is exhibited in the Chemiftry 
Plate III. fig. 3, clefcription as follows : A is a balloon of 
glafs or cryital, holding about thirty pints, having a large 
opening, to which is cemented the plate of copper B 
pierced with four holes, in which four tubes terminate. 
The firft tube H h is to be adapted to an air-pump, by 
which the balloon may be exhaufted of its air. The fe- 
,cond tube gg communicates by its extremity M, with a 
The fourth tube, GL, contains a metallic wire, having 
a knob at its extremity L, intended for tranfmitting the 
eieClrical fpark from L to d, on purpofe to Jet fire to the 
hydrogen gas : this wire is moveable in the tube, that 
the operator may be able to move the knob L to or from 
the extremity d of the tube D d. The three firft-men- 
tioned tubes are all provided with flop-cocks. 
That the hydrogen gas and oxygen gas may be as much 
as poflible deprived of water, they are made to pals, in 
their way to the balloon A, through the tubes M and N, 
of about an inch diameter; and thefe are filled with lalts, 
which, from their deliquefeent nature, greedily attraCt 
the moifture of the gas: fuch are the acetit of potafh, 
and the muriat or nitrat of lime. Thefe falts mult only 
be reduced to a coarfe powder, that they may not run 
into lumps, and prevent the gafes from palling through 
their interfaces. 
Being provided with a fufficient quantity of the oxy¬ 
gen and hydrogen gafes (the latter in the proportion of 
two to one of the former,) and having adjulted every 
thing properly, as above-direCfed, the tube H h mull be 
adapted to an air-pump, and the balloon A exhaufted of 
its air. Next admit the oxygen fo as to fill the balloon, 
and then by means of preflure force a ftream of hydro¬ 
gen through the tube D d, to which fet fire by an elec¬ 
trical fpark fent down the wire contained in the tube 
GL. By means of the above-deferibed apparatus, the 
mutual combuftion of thefe two gafes may be continued 
for a long time, as the operator has the power of fup- 
plying them to the balloon from their refervoirs, in pro¬ 
portion as they are confumed. In proportion to tire ad¬ 
vancement of the combuftion, there is a depofition of 
water upon thy inner furface of the balloon A : the wa¬ 
ter gradually increafes in quantity, and, gathering into 
large drops, runs down to the bottom of the veflel. / It 
is eafy to aicertain the quantity of water collected, by 
weighing the balloon both before and after the experi¬ 
ment. Thus we have a twofold verification of the com¬ 
ponent parts of water, by afeertaining both the quanti¬ 
ties of the gafes employed, and of the water formed by 
their combuftion : thefe two quantities muft be equal to 
each other. By an operation of this kind it was afeer- 
tained, that it required eighty-five parts by weight, of 
oxygen, united to fifteen parts of hydrogen, to compofe 
one hundred parts of water. This decompofition and 
recompofition of water is perpetually operating before our 
eyes, in the temperature of the atmofphere, by means of 
compound eleftive attractions. The phenomena atten¬ 
dant upon vinous fermentation, putrefaftion, and even 
vegetation, are produced, at leaft in a certain degree, by 
the decompofition of water. It is very extraordinary that 
this faCt fiiould have been fo long overlooked by natural 
philolophers and chemifts. Indeed it ftrongly proves, 
that in chemiftry, as in natural philofophy, it is extremely 
difficult to overcome prejudices imbibed in early educa¬ 
tion, and to fearch for truth in any other road than the 
one we have been accuftomed to follow. 
Another experiment of Lavoifier’s may be offered for 
the recompofition of water. -Under a large bell-glafs 
filled with atmofpherical air, and inverted over mercury, 
introduce a lamp containing alcohol; flick a morfel of 
phofphorus upon the match, and light it with a bent 
iron-rod, made red-hot, parted underneath the glafs. The 
mercury foon rifes in the glafs, and fliews by its rifing, 
in lpite of the heat, a rapid and confiderable diminution 
of air; after combuftion, a great quantity of drops of 
water is vifible on the fides of the glafs and on the fur- 
face of the mercury. This water, gathered with care, 
always 
