C I-r E M I S T R Y. 
156 
and that of vapour, or gas. Ice is a cryftallization more 
or left regular, tranfparent, very lapicl, elaitic, fuiible at 
a temperature above 32° of Fahrenheit’s thermometer, 
and which buffers the el'cnpe of much caloric from its in¬ 
terior, iii feveral combinations. Ice at 32 0 abforbs ua° 
of heat in melting, or i'uch a quantity of caloric as would 
raii'e a body of water of equal bulk with itfelf to 144°. 
Its capacity, therefore, is not the fame with that of liquid 
water, which is owing to the difference of its ffate, as 
has been laid above, under theadtion of caloric. 
Whenever liquid water lofes much caloric on enter¬ 
ing into any combination, it ought to be conlidered 
as Iblid in it; frequently it is even much more lo than 
ice at 32 0 ; whence arifes the folidity of mortars, or ce¬ 
ments, of which flaked lime forms a part. Water remains 
eternally 1'olid on mountains, cooled for ages by the pre¬ 
fence of ice, and underneath the poles. In thefe places 
it forms l'olid rocks, or white concretions almoft fimilar 
to (tones. 
Liquid water is pure, infipid, deftitute of fmell, and 850 
times heavier than air. It forms rivers, brooks, ponds, 
fprings, rivulets, &c. It occupies the cavities, furrows, 
and generally (peaking all the loweil parts, of the globe. 
It is very l'eldom pure; for it diflblves, in the earth, and 
on its iurface, air, Inline gales, and terrellrious falts: 
it afts even on the molt l'olid Hones, which it diflblves, 
carries along in its courfe, depolits, and criftallizes. 
Hence it has been named the grand lolvent of nature. 
By it are produced various phenomena, and it is one 
of the molt powerful agents, by which the Iurface of the 
globe is inceifantly modified. Its motions, its currents, 
its aflion, have gradually changed the nature of mine¬ 
rals, and created a kind of new world on the face of the 
old. Accordingly all the waters of the earth contain 
l'ome fubftance or other, foreign to the nature of water ; 
the prefence of which is dilcernable from the increafe 
of their lpecific gravity, their tafte, more or lei’s flat, 
earthy, and crude, and the difficulty with which they 
boil, drefs pulf'e, or diffolve loap. The more free any 
water is from thefe properties; which are repugnant to 
its effential charafter, the greater is its purity. Water 
flowing in a fandy channel, and expofed to the open 
air, is fufliciently pure for the purpofes of life, and 
moft of the ul'es of the arts. On the contrary, that 
which traverfes chalk, gypfum, and marbles, or ftagnates 
on turf, bitumen, and ores of metals, or in fubterranean 
cavities far from the contadt of the atmofphere, is more 
or lefs impure. The art of correcting hard or impure 
water by chemiflry, coniifts in expofing it to the atmof¬ 
phere, agitating it in contact with the air, boiling it, 
diftilling it, and afterwards combining it with air. Fre¬ 
quently the addition of allies, alkalis, or weak acids, 
ierves to diminifh the bad qualities of water; and fome- 
times even completely removes them. Moft adventi¬ 
tious fubltances, which diminilh the purity of water, being 
either much more volatile or much more fixed than it, dii- 
tillation is the moll certain method of obtaining pure 
water. For this reafon chemiffs always employ diftiiled 
water in their experiments. 
Liquid water, being a combination of ice at 32°, and 
fiich a quantity of caloric as would have been 1'ufHcient 
to raife the water to 144°, on the addition of caloric be¬ 
comes rarefied: when it is railed to a temperature of i 84°, 
it aflumes the form of gas; it is vapour: in this Hate, it 
is far lighter than liquid water, it occupies a much more 
extensive (pace, it eafily penetrates all bodies, it readily 
diflblves in air, and itsexpanflve force, from the increaie 
of its temperature, renders it capable of moving enormous 
weights, driving the fleam-engine, &c. As liquid water 
•abforbs air, which renders it light, air alio abforbs and 
diflblves water. This is the caufe of water’s evaporating. 
The folution of water in air, is dry and invifible as air 
itfelf: it is proportionate to the temperature of the at- 
molphere. The hygrometer does not indicate with pre- 
idfion this water, for it is not effected by a complete iolu- 
tion of water in air, but moves according to the quantity 
of water which is juft going to be dififolved, and more es¬ 
pecially oFthat which is precipitating from it. 
Water is not a Ample fubftance, as had long been fup- 
pofed. By burning with rapidity a number of coinbuf- 
tible bodies, more or lei's heated, as charcoal and pit-coal 
already on fire, red hot iron, zink melted and red-hot, 
oil, &c. water is decompofed, yielding to thefe combuf- 
tible bodies the oxygen it contained. In proportion as 
the oxygen of the water becomes fixed in the combufti- 
ble bodies which it burns, its other principle capable of 
difiblving in caloric forms the inflammable gas which is 
evolved. As this fecond principle is one of the elements 
of water, it has been called hydrogen, and its elaitic fluid 
-folution in light and caloric, hydrogen gas. The dil'en- 
gagement of this principle in the form of gas, which 
takes place wherever water is decompofed by a combufti- 
ble body, is the caufe of a great number of detonations 
and fulminations. The hydrogen gas produced in vari- 
ous experiments always originates from water, either in 
confequence of a preceding decompofition, in which it 
had been combined in the flate of fixed hydrogen with 
one of the l'ubftances employed, or from a decompofition 
of water actually taking place in the experiments them- 
lelves. All the inflammable gas, therefore, proceeds from 
water. Reiterated experiments have proved, that water 
contains about eighty-live hundredth parts of oxygen and 
fifteen of hydrogen. The recompolition of water, one 
of the grandelt difeoveries of modern chemiflry, confirms 
the analylis of this body; for, on uniting by combultion 
eighty-live parts of oxygen with fifteen of hydrogen, a 
hundred parts of pure water are obtained. 
When water is decompofed by a combuftible body, this 
is effected by meansofadouble affinity ; that of the oxygen 
of the water for the combuftible body, and that of its 
hydrogen for caloric. For this reafon, the more caloric 
matter is employed in the experiment of decompofmg 
water by means of iron, charcoal, or the like, the f'ooner 
is the water decompoled. From this neceffity for an ex¬ 
treme abundance of caloric in the operation, it is ealy 
to conceive how the hydrogen, one of the elements of 
the water, acquires a levity fo far beyond that of the fluid 
from which it is derived : in faCt, while a cubic foot of 
water weighs feventy pounds, a cubic foot of pure hy¬ 
drogen gas weighs only fixty-one grains. Hydrogen gas, 
though always produced by the decompofition of wa¬ 
ter, carries along with it vaiious fubltances, either fuf- 
pended or diifolved in it, according as the bodies from 
which it is extricated are more or leis Ample. Thus it is 
mingled with azotic gas, carbonic acid gas, or vital air ; 
or it holds in folution, water, carbon, fulphur, phofpho- 
rus, arfenic, oil, alcohol, ether, &c. From the difference 
of thefe adventitious fubltances which it contains, it varies 
in fmell, weight, and inflammability, the colour of the 
flame it yields, its aCtion on different bodies, and all'o in 
the products diftinCt from pure water which it affords in 
burning. Hence are derived the leveral fpecies and de¬ 
nominations of inflammable gas admitted by authors, of 
which hydrogen gas always conftitutes the general balls. 
Hydrogen gas being one of thole natural fubltances 
that contain moll caloric, it is among the number of 
combuftible bodies, which give out moft, and conlequent- 
ly afford molt heat in burning. Hence all compound 
combuftible bodies of which hydrogen conftitutes the 
bafis, fuch as oils, fats, and in general all that originate 
from organized bodies, yield, during the procefs of burn¬ 
ing, a confiderable quantify of heat. Wood, oil, pit- 
coal, bitumen, alcohol, ether, &c. are of this kind. It 
follows, alfo, from what has been laid, that thofe conn 
pound combuftible bodies, which contain much hydrogen 
in their compoiition, necellarily require a large portion 
of oxygen in burning, and afford water as a produCt of 
their combultion, in proportion to the quantity of hy¬ 
drogen they contain. Thus a pound of alcohol, on bein 3 
burnt, yields more than a pound of water. The com- 
bultibis 
