2o6 C H E M 
i- loth lefs than that of water; but it muft obvioufiy 
vary in proportion to the quantity of air which the wa¬ 
ter contains, the degree of cold to which it is expol'ed, 
the fuddennefsof the congelation, &c. Hence ice form¬ 
ed from water previoufty deprived of its air is found to 
be harder, more tranfparent, and heavier, than common 
ice. The property of expanfion by freezing is common 
to many other bodies, inch as butter, tallow, wax, &c. 
And not only water, but home of the metals (iron for 
example), appear to expand a little in palling from the 
liquid to the folid date. We have a proof of this in the 
very ltrong impreffions metals receive from the moulds 
in which they are call. 6. Its tranfparency is lefs than 
that of water, in conlequence of the bubbles of air which 
it contains, at leaft in iuch malfes as are not regularly 
cryftallized. This may be eafily feen by an attentive 
examination of a piece of ice; and, if the cavities be 
opened under water, the air is diltindlly feen to blue out 
in bubbles. 7. It melts at fome degrees of temperature 
above o° in Reaumur’s fcale (or 32° of Fahrenheit), the 
liquefaftion proceeding gradually from the furface to the 
internal parts. Ice evaporates all'o at a temperature be¬ 
low that at which it melts into water. This is proved 
not only by the dilappearance of hoar froft from polifhed 
plates of metal during their expofure to dry frofty winds, 
but alfo by direft experiments, in which the weight of 
folid pieces of ice was diminifhed by expofure in the lame 
circumltances.- This evaporation or folution of ice-in 
air takes place likewile in durations where there is no 
current of air, and even in air confined in cloJe 'vellels. 
8. fa its pafiage from the lolid to the fluid Hate, it pro¬ 
duces cold in the. furronnding atmofphere. Modern ihe- 
jr.ids think that it ablorbs heat in meltings and that this 
abforption is equal with regard to the quantity of caloric 
which becomes fixed, and the quantity of heat which is 
dilengaged when it becomes congealed. All bodies ca¬ 
pable of freezing and melting, exhibit tlie fame appear¬ 
ance, according to the different temperatures to which 
they are expoled. Hail and fnow are only modifications 
of ice; hail may be confidered as produced by the lud- 
den difengagement of the eleftric fluid, which tends to 
render water fluid. 
Of Fluid Water. —In this'ftate, water has feveral 
peculiar properties, diftimfl from its other modifications. 
Its tafte is lefs lively, fince fome' philofophers regard it 
as infipid. It is elaftic. Its flate of liquid aggregation, 
renders its ftrength of aggregation greater. It unites 
with a great number of bodies, and even promotes great¬ 
ly their reciprocal combination. It does not unite with 
light, which only goes through it. Caloric dilates it, 
and brings it to the gafeous ftate : its pafiage from a ftate 
of liquidity to thht of an aeriform fluid conftitutes-its 
ebullition. 
The weight of the atmofphere has a lingular influence 
on the ebullition of water; in proportion as this weight 
is greater, fo much the more does itoppole the tendency 
in the water to dilate and aflume the form of vapour. 
When the weight of the atmofphere is taken oft' by means 
of an air-pump, and water is "placed in the receiver heat¬ 
ed previoufiy to 40°, we oblerve it to boil with great 
violence, and become converted into vapour. And for 
this reafon, liquors eafily evaporated and very volatile, as 
alcohol, ether, ammoniacal gas, &c. lofe the greateft 
part of their ftrength on high mountains. 
If water be heated in doled vellels, with an apparatus 
proper to receive the vapours, thele laft, when condenf- 
ed by cold, form di(tilled water. By this means, it is 
bbtained pure, and leparate from the faline and earthy 
matters by which natural waters are almoft always con¬ 
taminated. and which do not rife with the vapour. Che- 
rnifts, who require very pure water for their experiments, 
procure it by diftillation. They put river or Ipring wa¬ 
ter into a cucurbit of copper, lined with tin, to which 
a head of the fame metal, with a refrigeratory, contain¬ 
ing very cold water, is adapted ; and the diftilled water 
_ 2 
S T R Y. 
is received in very dean glafs vciTels. It is proper to be 
oblerved, that in order to have very pure diftilled water, 
the veflels Ihould be ufed for no other purpole. The 
vcffels intended to„diftil quickly, fliouid be made on the 
new principles; that is to lay, the cucurbit and its head 
Ihould be of a flattened figure, their horizontal being 
much longer than their vertical diameter. Water obtain¬ 
ed by careful diftillation, thus conduced, is perfectly 
pure. Chemifts formerly made ufe of i'now or rain water; 
but it is at pTefent well known, that thele waters often 
contain foreign bodies in Solution. 
Diftilled water has a flat or faint tafte, and caufeS a 
fenfation of weight at the ftomach ; but by being'Itrongly 
agitated in contacl with air, it acquires a lively tafte, and 
may be drunk without inconvenience. Diftillation makes 
no change in pure water, except that of depriving it of 
the air it naturally contains, which gives it that frelh 
and lively tafte required to make it potable. Boerhaave- 
diftilled the lame water five hundred times, without ob- 
ferving any change produced in it. Some philolbphers 
have affirmed, at different periods, that water becomes 
changed into earth ; becaufe, at each diftillation, it leaves 
a certain quantity of earthy matter at the bottom of the 
veffel. M. Lavoifier has made experiments relpecling 
this fafl. Having weighed the vefiels be ufed in diftilling- 
water, as well as the quantity of water, and the relidue 
it affords, he has fhown that this earth is nothing but the 
matter of the vellels gradually corroded by the water. 
In addition to thele obfervations on fluid water, it may 
be oblerved, that its temperature ceafes to increale When 
the evaporation has arrived at a certain degree of rapi¬ 
dity ; that this ftationary point is higher in proportion 
to the difficulty the vapours find in making their eicape; 
that if the vapours be prevented altogetherfrom eicaping, 
as is done in the digefter of Papin, it will acquire, by the 
application of heat, a temperature approaching to igni¬ 
tion, add will diffolve or ail on earths and other bodies, 
which in other cafes it does not fenflbly afteil. 
Of Waterin Steam, or in the Gaseous State.— 
To convert wafer into gas, Lavoifier arid La Place firft 
made the following experiment. Fill a glafs jar with 
mercury, and place it with its mouth downwards in a 
large faucer or difh filled with the fame ; pafs a little wa¬ 
ter under the jar, and fufpend this apparatus by means 
of a weight and pulley, fo as to give the mercury a heat 
of 95 or 100° by lowering it into a boiling copper full of 
pure water of nitre, or of fea-falt, as reprelented in the 
Chemiftrv Plate III. fig. 2. The water quickly rarefies, 
and fills all the capacity of the jar with {he gas. 
When water is thus reduced to the ftate of vapour by 
the aftion of fire, it acquires feveral properties, whicu 
it had not in its two former ftates of aggregation. Dr. 
Black firft difcovered that water, in palling from the li¬ 
quid Hate to that of an elaftic fluid, ablorbs a quantity 
of caloric, which becomes latent, or which does r.ot add 
to its temperature. It is perfefliy invifibie when receiv-* 
ed in the atmofphere, provided the thermometer Hands 
higher than 65°, and the air be not already too highly 
charged with humidity. If, on the contrary, the atrrioi- 
phere have a temperature below 55 0 , and be charged 
with humidity, the vapour cf water forms a whitifh 
cloud, fenflbly opake; which ariles from the va¬ 
pour not being abforbed, or dilTolved by the humid air, 
and confequently to a true precipitation. Its dilatation 
is i'uch, that, from an experiment made by Dr Black and 
Mr. Watt, it was found that water in the form of fteam 
occupies,a fpace fourteen hundred times greater than in 
its ordinary liquid ftate. Its elafticity is fuch, as to pro¬ 
duce the inoft terrible explofions when confined. This 
power is ufefully employed in mechanics, of which ap¬ 
plication the engine for raifing water, commonly called 
the fteam engine, is an admirable inftance, well known 
both to philofophers and artifts- According to one of 
the moft conftant laws of the affinity of compolition, it 
has a fti'onger tendency to combination in this ftate,. 
wherein 
