CHEMISTRY. 
of the lime, as it is more or lefs perfeflly calcined; its 
previous flaking, with a greater or lei's quantity of water, 
or the flaking of it at the time of mixture ; the nature of 
the land with regard to its magnitude, its angular or 
round figure, as well as its degree of moiiture; produce 
very conliderable differences in the feveral kinds of mor¬ 
tars. Clay baked in bricks, or puzzoiana, which is clay 
baked by volcanic fires, and altered by expofure to air, 
are likewife added to lime in the making of mortar. 
Though lime, as well as filiceous earth, be perfectly 
infufible alone, yet if they be heated together, the pro¬ 
portion of the former being much the greateft, they melt, 
as has been obferved by Meftrs. d’Arcet and Gerhard. 
Lime likewife ferves as a flux to one-third of its weight 
of alumine: it appears to have a ftronger affinity with 
this earth than with filex, as Kii wan informs us. The 
mixture of thefe three fubftances melts ftill more eafily 
and completely than lime with either of them fingly ; fo 
that one part of lime, and one of alumine, will lerve to 
fufe two parts, or even two and a half, of filiceous earth : 
this fa£l fhews the caufe why many hard Hones giving 
fire with Heel, and of a quartzofe nature, melt when ex- 
pofed to a ftrong heat; the combination, or Ample mix¬ 
ture, of calcareous earth and clay, is the caufe of their 
vitrefcibility. One part of calcareous earth enters into 
f ufion with half a part of magnefia: the gflafs, formed by 
this mixture, afterwards diltolves, and completely meits 
a quantity of filiceous earth equal to the lime it con¬ 
tains : equal parts of filiceous earth, magnefia, and lime, 
melt therefore by heat into a perfect glais. 
The intimate nature of lime is not known. The early 
chemifts, defirous of explaining, by phyfical realoning, 
the phenomena exhibited by lime in its combinations, 
and more efpecially in its extindlion, referred its caule 
to the particles of fire fixed in the calcareous Hone during 
its calcination. This was the theory of Lemery. M. 
Meyer did not admit that pure fire was capable of com¬ 
bining in this manner, and therefore afferted, that it ex- 
ifted in lime united with a peculiar acid : this l'ubtle kind 
of fulphur was the acidum pingue or the caufticum of this 
chemift; but his do&rine, though occalionally brought 
forward unde; different names, has been overthrown by 
a feries of experiments, which have completely fhewn its 
fallacy. Many modern chemifts believe, that the matter 
of heat exifts in a combined Hate in lime, and that the 
light perceived by Meyer and Pelletier, with the ebulli¬ 
tion, the evaporation of the water, and the peculiar fatty 
fmell during the extinction of the lime, are confequences 
of its difengagement. Thefe obfervations fhew, that the 
principles and compofition of lime are yet unknown, and 
that we cannot, with any certainty, decide whether it is 
the produft of an attenuation, or peculiar preparation of 
tiie filiceous or aluminous earths; though that opinion 
appears probable to lbme of the greateft naturalitts. It 
feems indeed to be out of doubt, that it is formed by 
marine animals ; that its conftituent parts are united 
and combined in the water during the life of thefe orga¬ 
nic beings ; and that azot is one of its conftituent parts. 
But it muft be confeffed, that this fketch is not ye: fuffi- 
cient for the conviftion of modern philofophers, vho do 
not form their opinions decidedly, unlels in confequence 
cfrepeated and accurate experiments. 
Lime is employed in a great number of arts, and efpe¬ 
cially in building. In medicine, diluted lime-water is 
adminifterecl with fuccefs; in the cure of ulcers, &c. it 
has been cfteemed as a powerful lithontripfic; but re¬ 
peated trials have fhewn, that it is not always attended 
with the defired fuccefs ; and that its ufe, long continu¬ 
ed, produces an alteration in the animal fluids of a fcor- 
butic or feptic nature. 
Barytes. —This was firft called ponderous earth, terra 
ponderofa , by Gulin anu Scheele, two Swedilh chemifts, 
who found it to exiffc in ponderous fpar: but Bergman 
gave it the name of barytes, from ( 3 Gr. heavy. It is 
found always united with fulphuric and carbonic acids, 
i 
225 
taking a blue or green colour from fire. On its nature 
and properties we have been pretty full in the article Ba¬ 
rytes, in our fecond volume, page 767. The following 
is the procefs of Fourtroy and Vauquelin for obtaining 
k pure, by decompcfing nitrat of barytes by heat: Take 
nitrat of barytes well cryftallized ; expofe it to the aftion 
of fire in a porcelain retort, or rather in a crucible placed 
upon burning coals. The nitrat melts, fwells, furniflies 
much oxygen and azotic gas, but with hardly any nitrous 
vapours; when no more elaftic fluids are difengaged, there 
will be found in the broken retort when coid, a grey mat¬ 
ter, folid, fomewhat porous, of a bitter tafte, and hotter 
than quicklime : this is pure barytes. 
This earth melts under the blow-pipe on a coal, boils 
up, and forms globules, which foon penetrate the coal. 
In the air it becomes turbid, breaks, burfts, fwells, heats, 
and whitens ; melting thus rapidly, it abforbs o'zz of its 
weight of water and carbonic acid. It turns fyrup of 
violets of a green colour. It abforbs water with extreme 
avidity, melts with a hilling noife like lime, heats con- 
fiderably, folidifies the water, and forms compages like 
beaten plafter, flicking hard upon glafs. A little water 
changes it into a white powder. Covered entirely with 
water, it diflolves wfith a violent biffing; then cryftallizes 
in tranfparent needles, which lie in heaps together, like 
the molecules of plalhed mortar. Cold water dilTolves 
one-twenty-fifth part of its weight; boiling water more 
than half, depofiting, as it gets cold, beautiful tranfpa¬ 
rent prifms, which become turbid, and pulverize in the 
air. A folution of barytes is fooner covered wfith a cruft 
or pellicle by expofure to the air, and is more plentifully 
precipitated, by carbonic acid, than lime-water is. Phoi- 
phoric and phofphorus acids haften the folution of ba¬ 
rytes ; and the precipitates are re-diflblved by means of 
the exceis of each refpefifive acid. With fulphuric and 
fulphureous acid, it forms infoluble falts. It has been 
endeavoured to combine barytes with iome other earths ; 
but a per left vitrification has never yet been produced. 
Strontian, or Strontites.— A great quantity of 
this earth has lately been difcovered in France : M. Le- 
lievre communicated to the national inftitute f at Paris, 
that fulphat of ftrontian had been found in a clay-pit at 
Bouvron, near Toul, in the department of La Meurthe. 
M. Dolomieu at the fame time (hewed fome which he had 
brought with him from Sicily ; and which, as well as the 
preceding, had been analyzed by Vauquelin. The name 
comes from Strontian , in Argylefhire, Scotland, where it 
was firft found, united to carbonic acid in a fulfil called 
gneis, in the lead-mines at that place. 
Sulpnat of ftrontian is converted into a fulphure by 
the help of charcoal, having previoufly feparated the car- 
bonat of lime from it by means of an acid. Then the 
fulphure is to be decompofed by nitric acid; and, by 
heating this nitrat in a crucible, it is entirely decom¬ 
pofed, and the ftrontian remains pure. Expoled to the 
air, it becomes turbid, and attracts the carbonic acid 
from the atmofphere. It is foluble in water, and cryf¬ 
tallizes in cooling. It is foluble in 250 times its weight 
of boiling water; but of cold water it requires more. If 
the lolution be expoled to the air, it becomes covered 
with a pellicle like barytes, and forms carbonat of ftron¬ 
tian. The lame effefil is produced by letting air into the 
folution with a blow-pipe. 
This earth combines very well with acids ; and pro¬ 
duces falts, which will be examined hereafter. The Itron- 
tian which js obtained by the decompofiticn of the ni¬ 
trat, combines very well with lome combuitible bodies, 
as phofphorus, fulphur, and fulphurated hydrogen. Thele 
combinations are produced in the lame manner as thole 
with barytes, and poilels properties analogous to thole 
combinations. 
Of ALKALIS. 
Alkalis are bodies either folid or liquid ; in tafte acrid, 
caultic, and pungent or iixivial; they are very foluble in 
water; 
