C H E M I 
folutions, fermentations, 8 cc. The third divifion lies be¬ 
tween the 88th and 100th degrees of the thermometer. 
In this temperature the acid or acetous fermentation in 
vegetables is bell carried on, and plants are fuccefsfuily 
dried for practical ufe. It is adopted for fome faline i'o- 
lutions, and to promote fermentations. The fourth di~ 
vifion is at, or near, the temperature of about 14.5 0 . 
This is called the mean degree of heated water, and is 
that of the veffels called balneum marias. It deltroys the 
organization of animal matters, and volatilizes the more 
lubtile parts of effential oils, efpecially the lpiritus rec¬ 
tor. It is ufed in the diftillation of vegetables and ani¬ 
mal matters, whofe phlegm and principle of fmell are 
intended to be feparated. The temperature of boiling 
water, or in°, is ufed in decoftions, the extraction of 
effential oils, Sec. 
The firlt divifion of heat above boiling water, melts 
fulphur, burns organized matter, or gives a low red heat 
to glafs velfels. The fecond extends from the fufion of 
the fofter metals, fuch as lead, tin, or bifmuth, to that 
of the fofter kinds of glafs. The third divifion may be 
conlidered as including the fufion of metals of a middle 
confidence, fuch as antimony, filver, and gold. The 
fourth l'erves to bake porcelain, and fufes the more re- 
fraCtory metals, fuch as cobalt, copper, iron, &c. The 
laft and higlieft of all is found in the focus of the burning 
glafs. This extreme heat calcines, burns, and vitrifies, 
in a very fliort time, all bodies fufceptible of fuch a 
change. A fimilar degree of heat may be excited by a 
llream of vital air or oxygenous gas thrown upon char • 
coal, by means of the bellows or blow-pipe. M. Monge 
is of opinion, that by prefenting atmofplieric air in a 
ftate of compreflion, to combuftible bodies in a date of 
inflammation in the furnace, an effeft may be produced 
fimilar to that excited by vital air. This procefs may 
hereafter be applied to operations in the large way. 
Though thefe divifions above boiling water are deter¬ 
mined by phenomena well known to chemiils, their ad- 
meafurement has not the defired precifion. A11 inftru- 
ment capable of indicating with exaCtnefs the degrees 
employed in thefe operations, would be an acquifition of 
reat value and importance. Mr. Wedgwood has con- 
rufted a pyrometer for this purpofe; it is formed of 
fmall pieces of clay half an inch in diameter. Thefe 
pieces, when contracted by heat, advance to a greater or 
lefs diftance between two rules of copper convergent to¬ 
wards each other, upon a plate of the fame metal. In 
this manner, by means of a fcale drawn upon thefe rules, 
the degree of contraction, and confequently bf heat, 
which they have experienced, is afeertained. 
The heat required in chemical operations, is produced 
by the combuftion of charcoal, or common mineral coal. 
For this purpofe, various furnaces of different forms and 
names are conftruCted, according to the purpofe they are 
intended to anfwer. The manner of communicating 
heat to bodies in the various chemical proceffes, likewile 
<delerves attention. If the combuftible matter be applied 
to the fubftance itfelf or the veffel immediately contain¬ 
ing it, the operation is faid to be performed by a naked fire. 
If any fubftance be placed between the fire and the veffel 
containing the matter under examination, the interpofed 
fubftance is called a bath. Hence the names balneum ma- 
riae, or water bath, fand bath, dung bath, cinder bath, &c. 
The form of the veffels employed in the treatment of 
bodies by fire, and the different phenomena prefented by 
the matter expofed to its aCtion, have occafioned a con- 
fiderable number of operations to be diflinguifhed by 
particular names. Such as roafting, calcination, fufion, 
reduftion, vitrification, cupellation, cementation, ltra- 
tifkation, detonation, decrepitation, fulmination, fubli- 
mation, evaporation, diftillation, rectification, concen¬ 
tration, digeftion, infufion, decoftion, lixiviation-. and 
thefe operations, performed by the agency of fire, eon- 
ftitute much of the practical part of chemiftry. 
Roafting is a procefs by which mineral fubftances are 
divided, fome of their principles being volatilized, and 
Vox.. IV. No, 188. 
S T R Y. tSq 
others changed, fo as to prepare them for other opera¬ 
tions, to which this may be regarded as preliminary. 
Minerals are fnbjeCted to this, in order to feparate their 
fulphur or arfenic, and to render them more pulverable 
or friable. In the fmall way, this is'done in crucibles, 
roafting nets, or capfules of earth or iron, and generally 
with accefs of air. Sometimes it is performed in clpfed 
velfels, for which purpofe two crucibles are uluaily luted 
mouth to mouth. 
Calcination is, as it were, a more advanced ftage of 
the procefs of roadting. Minerals are by this deprived 
of their water, calcareous (tones are thus converted into 
lime, and the mefals into metallic oxyds. The fame vcf- 
jfels are employed for this purpofe as for roafting. 
By fufion, bodies are made to pafs from the folid to 
the fluid ftate, in confequence of the application of heat. 
Salts, fulphur, and metals, are the chief bodies fubjeCt- 
ed to this procefs. Crucibles of baked clay of porcelain, 
of courfe grit of iron and platina, of various kinds and 
figures, with metallic cones or ingot moulds, are the in- 
llruments chiefly ufed. Thefe laft give the figure to the 
matter, which, after being melted and cooled again, has 
the form of a bar, or ingot, or a button. The facility 
with which metals may be united by fufion, after they 
have been divided, is probably the circumftancfe that in¬ 
duced mankind to ufe them as the mediums of exchange, 
or figns of value of all other commodities. 
In reduction or revivification, the oxyds of metals are 
reltored to their metallic ftate by the afliftance of fire, 
with charcoal or oils, or other inflammable matter. 
Vitrification, is the fufion of fubftances capable of af¬ 
firming the briglitnefs, tranfparency, hardnels, and other 
properties, of glafs. Verifiable earths with alkalis, and 
metallic oxyds, are the principal matters fubjeCtea to this 
operation. 
Cupellation is the purifying of perfeSl metals, and the 
extraction of the imperfect mixed with them, by means 
of aft addition of lead. This promotes the vitrification 
of the imperfeft metals fo that thefe laft are carried off, 
and the perfeCt metals are left nearly pure. The name of 
this operation is taken from the veffels made ufe of, which 
are a kind of flat crucibles, fimilar to fmall cups, called cu¬ 
pels. Thefe are formed of the earth of bones, which, on 
account of its porofity, eafily imbibes the glafs of lead. 
Certain powders made ufe of for including particular 
bodies intended to be changed by their aCtion, in clofe 
veffels, fubjeCted to heat, are called cements. Thus it is 
that iron is cemented with powder of charcoal to con¬ 
vert it into fteel; and glafs with nlafter orft’and, to con¬ 
vert it into a kind of porcelain. Cementation, in certain 
cafes, requires a very ftrong heat. 
Stratification is a procefs nearly fimilar to the forego¬ 
ing : it confilts in the arrangement of various folid bo¬ 
dies in a crucible, or other veffel capable of refilling the 
fire. Thefe are generally in the form of bars or plates, 
and are blended with pulverable matters, capable of al¬ 
tering their nature. The form and the difpofition of 
thefe matters in beds or layers, ftrata fuper Jirata, has 
given rife to the name ftratification. In this manner 
copper or filver are treated with fulphur, in order to effeCt 
a combination. This procefs differs from fufion, calci¬ 
nation, or vitrification, only in the particular difpofition 
of the matters fubjeCted to it. 
Detonation is peculiar to nitre, and thofe matters of 
which it is a component part. It confilts in the greater 
or lefs noife produced by the explofion of thefe fubftance* 
•when heated, fuddenly or llowly, and by degrees in open 
or clofe veffels. Decrepitation which differs from deto¬ 
nation in its noife being much lefs, and in the kind of 
crackling found with which it is accompanied, is peculiar 
to fuch falts as burft afunder by heat, which caufes their 
water of cry flail ization to expand, and make its efcape. 
It is particularly oblerved in common fait or muriat of 
foda. Fulmination is a quick and fudden detonation 
obferved in fulminating gold, fulminating powder, and 
the combuftion of inflammable and pure air, &c. 
3 C The 
