/ 
' \ » 
CHE M I 
wherein its aggregation is the molt feeble, than in either 
t>f the two others. Chemilts have frequent occaiion to 
obferve with what rapidity water, in the Hate of vapour, 
diffolves (alts, foftens extractive and mucilaginous mat¬ 
ters, corrodes and calcines metals, &c. It is perfectly 
dilfolved in air. When it is flowly depofited out of the 
atmoiphere, it conllitutes dew. This diflolutiqn is per¬ 
formed in the lame manner as thole of falts in water. 
One of the mod lingular phenomena relpefting water in 
a Hate of vapour, is the property it poffeffes of accelerating 
the combuition of oil when on fire ; as is leen in the ex¬ 
periment of the eolipiie applied to the enameilers lkmp, 
or to common fires of pit-coal or wood, or fats in a lfate 
of inflammation, which cannot be extinguiflied by water, 
and even the burning of,which it increafes. Thefe phe¬ 
nomena induced Boerhaave to conclude that flame is, 
for the moil part, compofed of water. Laflly, Water in 
the form of vapour, and diffoived in the air, is condenf 
ed and precipitated in part when expyfed to a degree of 
cold fome degrees above the freezing point, it then re¬ 
lumes its liquidity, as is feen in the falling dew. Some¬ 
times, when the cold is beneath the freezing point, it is 
converted into fmall cryflals of ice. Such is the origin 
of thofe ramified incruflations of ice formed on the in¬ 
ternal furface of the glals in windows during in ten (e 
frofls; and the fame caufe in Siberia, and other very 
cold climates, converts the moiflure of the breath into 
a kind of fnow. 
Chemical Properties of Water. —There are fix 
kinds of water prefented to our view ; rain-water, Ihovv- 
waier, the water of hail, of fprings, of lakes, of rivers, 
and of the lea. Waters are difiinguifhed alio from the 
manner in which they aft upon the flomach, upon loan, 
boiling of vegetables, &c. in hard or loft water. Such 
are waters which contain faline fubHances, carbonic acid, 
clay, iron, extrafts of vegetables changed by putrefac¬ 
tion. All thefe waters are improper to drink. 
From the union of water and caloric, the produfts are. 
Boiling water, difiilled water, and water in vapours. 
Water unites in two ways with atmospherical air: it ab- 
forbs the elaflic fluid, aiid becomes charged with it while 
in its liquid Hate; it is even demonltrated, that to this 
combination with air its frelh and agreeable taHe is owing. 
Water may be deprived of its air either by ebullition or 
diflillation. 
To try whether water is aerated or not, put in fuiphat 
of iron well ciyltaliized. If the water be net aerated, 
the cryHal remains tranfparerit; the contrary happens if 
the water be aerated, for it attrafts a yellow duH. Boil¬ 
ing water, and diltiiled water collefted with care, are 
examples of water not aerated. Thefe waters may alio 
lie tried with metallic fulphures : the changes which 
fake place fhew the prefence of air. The prelence of air 
in water is fhewn alio by the concentrated- lulphuric 
acid. When the acid is poured out, there is effervel- 
cence ; the two fluids concentrate, they work upon each 
other; and the effervefcence is only the dilengagement 
of the contained air; but this air is purer than atmoi- 
pherical air ; which proves that water, in difiolving air, 
has more hold upon oxygen than upon azot. If this 
experiment be made with a tube, on inverting it, the air 
will be leen to rife, and then you may weigh and calcu¬ 
late the quantity of air contained in the water; then by 
fiirring the acid, ltrire or channels appear, which (hews 
the mixture of the two liquids. But water with hydro¬ 
gen gas, has no aftion. 
Thefe.details on the chemical properties of water, have 
only fhewn it as a very powerful agent in combinations, 
and capable of uniting with a great variety of fubHances: 
but in many of thefe combinations it fuffers a Angular 
alteration, which was not difcovered till the year 1784. 
It had long been known, that water, in certain cafes, fa¬ 
vours combuflion, as in the enameilers’ lamp, the in¬ 
flammation of oil, at great fires, &c. but it was little 
thought that moll of thefe phenomena were produced by 
S T R y. 207 
the decompofiticm of the water; it Iras referved for the 
genius of Lavoiiier to carry this point to the degree of 
certainty and precifion to which it is now arrived. That 
eminent client ill tvas led to this difeovery, by having re¬ 
marked, with M. De la Place, that, when iiiflamjnable 
gas is burned with vital air in clofed veliels, pure water 
is always produced ; whence he concluded, that water 
was formed' in this experiment by the combination of 
pure and of inflammable gas, which he regarded as its 
conflituent principles, This theory of the nature of wa 
ter, by winch M. Lavoifier deprived it at once of its pre¬ 
rogative as a Ample body and as an element, met with 
fucli oppofition, as convincethhim that the deco.mpofition 
of water was a proof neceffaryto be added to the iynthe- 
tical examination of that lubflance. He therefore en¬ 
deavoured to decompole this fluid; by prefenting to it 
fuch bodies as might be expefted to feparate one of its 
principles. He allociated himfelf with M. Meufnier for 
the purpofe of making thefe inquiries; and thefe two 
philofophers rend a Memoir at the Royal Academy of 
Sciences, the aift of April 1784, wherein they eltablifh- 
ed that water is not a Ample lubflance, but is compoled 
of the bale of inflammable gas and pure air, or Qxygen, 
which may be e.dily decoflipofed, or. feparated from each 
other. Meffrs. Lavoiiier and Meufnier alio deduced, that 
this fluid is compoled of lix parts of oxygen, and one of 
the bale of inflammable gas ; or, more accurately, o - 86 
ol the former, and o 14 of the latter of thefe fubltances: 
That iron, charcoal, and oils, having a greater affinity 
with oxygen than the lali has with the bale of inflamma¬ 
ble gas, leize it, and decompole the water entirely ; the 
inflammable air e lea ping in an elaflic form : that water" 
is recompofed by burning thele two kinds of air together, 
which, if carefully performed, affords a quantity equal 
in weight to that of the two fluids made ule of: that 
water is thus produced in a great number of chemical 
operations; as for example, when fpirit of wine or oils 
are burned under a chimney, adapted to the worm-pipe 
of a Hill, whofe other extremity is adapted to a recipient, 
a quantity of water is collefted, which is aim off always 
greater than that of the inflammable fluid made ule of; 
which is occafioned by the inflammable gas of thefe li¬ 
quids combining with the vital air of the atmoiphere, by 
which their combuition is maintained. Water is now 
therefore defined to be a compound of the b^le of vital 
air, or oxygen, and the bale of inflammable gas, or hy¬ 
drogen ; and as many bodies are inflammable in the Hate- 
of elaflic fluids, luch as alcohol, ether, the volatile, oils, 
&c. we diltinguilh this principle of water, in the aeri¬ 
form Hate, by the term hydrogenous gas- 
Decomposition of Water. —1. With charcoal. The 
product is carbonated hydrogen gas, and carbonic acid 
gas Take a tube of glals or porcelain ; pals it through 
a furnace, giving it a few degrees of inclination; put 
into the tube fome charcoal which has been previoully 
heated in dole veliels; to the upper extremity of the 
tube adapt a glafs retort containing a determinate quan¬ 
tity of diflilled w'ater; and to the lower extremity a bent 
tube or worm, which communicates with a doubly-tu¬ 
bulated bottle; to one of the openings or necks of the 
bottle another tube is adapted, which is to convey the 
aeriform fluids under a jar. Next, light a lufficient fire 
to keep the water boiling in the retort; at the fame 
time make a fire in the furnace where the tube is, and 
make it red-hot. When the operation is finilhed, only a 
little alhes remains in the tube; and under the jar is 
produced carbonic acid gas and carbonated acid gas. 
This decompofition may be wrought more quickly, but 
with lefs exaftnefs; put a red-hot coal underneath a 
bell-glals filled with water, and the refult is the fame. 
Put over mercury, in a little bell-glafs, a given quan¬ 
tity of pure, diflilled water, and foft iron in thin plates 
rolled up fpirally : the latter fubflance loon becomes rutt¬ 
ed, and hydrogen gas is difengaged. The iron is alio., 
burnt by the w'ater, producing a black oxyd. In the hot 
way 
