PHARMACY. 
*be poured into a heated mould anointed 
with tallow, never with oil, or what is still 
better, covered with a thin coating of 
chalk, which is applied by laying it over 
with a mixture of chalk diffused in water, 
and then evaporating the water completely 
by heat. To prevent the crucible from 
being broken by cooling too rapidly, it is 
to be either replaced in the furnace, to 
cool gradually with it, or covered with some 
vessel to prevent its being exposed imme- 
diately to the air. 
Fusion is performed with the intention of 
weakening the attraction of aggregation; 
or of separating substances of ditferent de- 
grees of fusibility from each other. 
Vaporization is the conversion of a solid 
or fluid into vapour by the agency of calo- 
ric. Although vaporability be merely a 
relative term, substances are said to be 
permanently elastic, volatile or fixed. The 
permanently elastic fluids or gases are those 
which cannot be condelised into a fluid or 
solid form by any abstraction of caloric we 
are capable of producing. Fixed sub- 
stances, on the contrary, are those which 
cannot be converted into vapour by great 
increase of temperature. The pressure of 
the atmosphere has very considerable effect 
in varying the degree at which substances 
are converted into vapour. Some solids, un- 
less subjected to very great pressure, are at 
once converted into vapour, although most 
of them pass through the intermediate state 
of fluidity. 
Vaporization is employed to separate sub- 
stances differing in volatility ; and to promote 
chemical action, hy disaggregating them. 
When employed with either of tliese 
views, no regard is paid to the substances 
volatilized, whether from solids, as in ustn- 
lation and charring ; or from fluids, as in 
evaporation ; or whfether the substances 
vaporized are condensed in proper vessels ; 
for example, in a liquid form, as in distilla- 
tion ; or in a solid form, as in sublimation. 
Or whether the substances vapoiized are 
permanently elastic, and are collected in 
their gaseous form, in a pneumatic appa- 
ratus. 
TJstulation is almo.st entirely a metal- 
lurgic operation, and is employed to expel 
the sulphur and arsenic contained in some 
metallic ores. Itis performed on small quan- 
tities in tests placed within a mnftle. Tests 
are shallow vessels made of bone ashes or 
baked clay. Muffles are vessels of baked 
clay, of a semi-cylindrical form, the flat side 
forming the floor, and the arched portion 
the roof and sides. Tlie end and sides are 
perforated with holes for the free transmis- 
sion of air, and the open extremity is placed 
at the door of tlie furnace, for the inspec- 
tion and manipulation of the process. The 
reverberatory furnace is commonly em- 
ployed for roasting, and the heat is at first 
very gentle, and slowly raised to redness. It 
is accelerated by exposing as large a surface 
of the substance to be roasted as possible, 
and by stirring it frequently, so as to pre- 
vent any agglutination, and to bring every 
part in succession to the surface. 
Charring may be performed on any of the 
compound oxides, by subjecting them to a 
degree ofheat sufficient to expel all their hy- 
drogen, nitrogen, and superabundant oxygen, 
while tlie carbon , being a fixed principle, re- 
mains behind in the state of charcoal. The 
temperature necessary for the operation 
may be produced either by tlie combustion 
of other substances, or by the partial com- 
bustion of the substance to be charred. In 
the former case, the operation may he per- 
formed iir any vessel which excludes the ac- 
cess of air, while it permits the escape of the 
vapours formed. In tire latter, the access 
of air must be regulated in such a manner, 
that it may be suppressed whenever the 
combustion has reached the requisite de- 
gree ; for if continued to be admitted, the 
charcoal itself would be dissipated in the 
form of carbonic acid gas, and nothing 
would remain but the alkaline and earthy 
matter, \vhich these snb.stances always con- 
tain. When combustion is carried this 
length, the process is termed incineration. 
The vapours wtiich arise in the operation of 
charring, are sometimes condensed, as in 
the manufacture of tar. 
Evaporation is the conversion of a fluid 
into vapour, by its combination with caloric. 
In this process, the atmosphere is not a ne- 
cessary agent, but rather a hindrance, by its 
pressure. This forms a criterion between 
chemical evaporation ami .spoptaneous eva- 
poration, which is merely tlie solution of a 
fluid in air. It is performed in open, shal- 
low, 01- hemispherical vessels of silver, 
tinned copper or iron, earthenware or 
glass. The necessary caloric may be fur- 
nished by means of an open fire, a tamp, or 
a tiirnace, either immediately, or with the 
intervention of sand, water, or vapour. The 
degree of lieat must be regulated by the na- 
ture of the substance operated on. In ge- 
neral, it .should not be greater than what is 
absolutely necessary. 
F.vapcration may be partial; producing 
