LABORATORY 
it is scarcely possible to offer (lie plan of 
a laboratory, which will be suitable to every 
person, and to all situations; or to suggest 
any thing more than a few rules that should 
be generally observed. Different apartments 
are required for the various classes of che- 
mical operations. The principal one may 
be on the ground iloor ; twenty-five feet long, 
fourteen or sixteen feet wide, and open to 
the roof, in which there should be contriv- 
ances for allowing the occasional escape of 
suffocating vapours. This will be destined 
chiefly for containing furnaces, both fixed 
and portable. It should be amply furnished 
with shelves and drawers, and with a large 
table in the centre, the best form of which 
i s -bat ot a double cross. Another apartment 
may be appropriated to the minuter opera- 
tions of chemistry ; such as those of preci- 
pitation on a small scale, the processes that 
l “quire merely the heat of a lamp, and ex- 
periments on the g-ases. In a third, of 
smaller size, m*y be deposited accurate ba- 
lances, and other instruments of considerable 
nicety, which would be injured by the acid 
fumes that are constantly spread “through a 
laboratory. & 
The following are the principal instru- 
ments that are required in chemical investi- 
gations ; but it is impossible, without enter- 
ing into very tedious details, to enumerate 
all that should be in- the possession of a prac- 
tical chemist. 
I . fc urnaces. 1 hese may either be form- 
ed tit solid brick-work, or of such materials 
as admit ot (heir removal from place to 
plaee.^ See Furnace, and Chemistry. 
-• 1* or containing the materials, which are 
to be submitted to the action of beat in a 
wind furnace, vessels called crucibles are 
employed. They are most commonly made 
of a mixture of tire-clay and sand, occasion- 
ally with the addition of plumbago, or black 
lead. The Hessian crucibles are best adapt- 
ed for supporting an intense heat without 
melting ; but they are liable to crack when 
suddenly heated or cooled. The porcelain 
ones made by Messrs. Wedgewood, are of 
nuifii purer materials, but are still more apt 
to crack on sudden changes of temperature ; 
and w hen used, they should therefore be 
placed in a common crucible of larger size, 
tin; interval being filled with sand. The 
black-lead crucibles resist very sudden 
.changes of temperature, and may be re- 
peatedly used ; but they are destroyed when 
some saline substances (such as nitre) are 
melted in them, and are consumed by a 
current pt air. For certain purposes cru- 
cibles are formed of pure silver or pialina. 
Their form varies considerably ; but it is ne- 
cessary, in all cases, to raise them from the 
bars of the grate, by a stand. For the pur- 
pose of submitting substances to the con- 
tinued action of a red heat, and with a con- 
siderable surface exposed to the air, a hol- 
low arched vessel, with a flat bottom, termed 
a mul'fle, is commonly used. See Che- 
mistry. 
3. Evaporating vessels should always be 
of a fiat shape, so as to expose them exten- 
sively to the action of heat. They are form- 
ed of glass, of earthenware, and of various 
metals. Those of glass are with difficulty 
made sufficiently thin, and are often broken 
by changes of temperature ; but they have 
a great advantage in the smootlmess of 
their surface, and in resisting the action °f 
most acid and corrosive substances. Eva- 
porating vessels ot porcelain* or YV edgwood’s 
ware, are next in utility, arc less costly, and 
less liable to be cracked. 1 hey are made 
both of glazed and unglazed ware. For 
ordinary purposes, the former are to he pre- 
ferred : but the unglazed should be employ- 
ed when great accuracy is required, since 
the glazing is acted on by several chemical 
substances. Evaporating vessels of glass, or 
porcelain, are generally bedded up to their 
edge in sand ; but those of various metals 
are placed immediately over the naked lire. 
When the glass or porcelain vessel is very 
tnin, and of small size, it may be safely 
placed on the ring of a brass stand, and the 
flame ot an Argand’s lamp, cautiously regu- 
lated, may be applied beneath it. A lamp 
thus supported, so as to be raised or lowered 
at pleasure, on an upright pillar, to which 
rings of various diameters are adapted, will 
be- found extremely useful ; and when a 
strong heat is required, it is advisable to 
employ a lamp provided with double con- 
centric wicks. 
4. In the process of evaporation, the va- 
pour for the most part is allowed to escape ; 
I but in certain chemical processes, the col- 
lection of the volatile portion is the principal 
object. I his process is termed distillation. 
See Distillation. 
1 he common still, however, can only be 
employed for volatilizing substances that do 
not act on copper, or other metals, and is, 
therefore, limited to very few operations, and 
on that account alembics and retorts are ne- 
cessary. See Chemistry. 
In several instances, the substance raised 
by distillation, is partly a condensible liquid, 
and partly a gas, which is not condensed till 
it is brought into contact with water. To 
effect this double purpose, a series of receiv- 
ers termed W oulfe’s apparatus is employed. 
See Chemistry. 
A hen a volatile substance is submitted to 
distillation, it is necessary to prevent the es- 
cape of the vapour through the junctures of 
the vessels ; and this is accomplished bv the 
application of lutes. The most simple me- 
thod of confining the vapour, it is obvious, 
would be to connect the places of juncture 
accurately together by grinding ; and ac- 
cordingly the neck of the retort is sometimes 
ground to the mouth of the receiver. This, 
however, adds too much to the expence of 
apparatus to be generally practised. 
Y\ hen the distilled liquid lias no cor- 
rosive property, (such as water, alcohol, 
ether, &c.) slips of moistened bladder, or 
ot paper or linen spread with flour paste, 
white of egg, or mucilage of gum Arabic, 
sufficiently answer the purpose. The sub- 
stance which remains, after expressing the 
oil from bitter almonds, and which is sold 
under the name of almond meal or flour, 
forms a useful lule, when mixed to the con- 
sistency of glaziers’ putty, with water or mu- 
cilage. 
For confining the vapour of acid or highly 
corrosive substances, the fat lute is we5l 
adapted. It is formed by beating perfectly 
dry and finely-sifted tobacco-pipe clay with 
painters’ drying-oil, to such a consistence that 
it may be moulded by the hand. The same 
clay, beaten up with as much sand as it -will 
3 
bear without losing its tenacity, with the 
addition of cut tow, or of horse-dung, and a 
proper quantity of water, furnishes a good 
lute,, which has the advantage of resistin'* a 
considerable heat, and is applicable in cases 
where the tat lute would be melted or de- 
stroyed. \ arious other lute? 1 are recom- 
mended by chemical writers ; but the few 
that have been enumerated are found to be 
amply sufficient for every purpose. See 
Lute. 
On some occasions, it is necessary to pro- 
tect the retort from too sudden changes of 
temperature by a proper coating. For glass 
retorts, a mixture of common clay or loam 
with sand, and cut shreds of flax, may be 
employed. If the distillation is performed 
by a sand heat, tire coating needs not to be 
applied higher than that part of the retort 
which, is bedded in sand; but if the process 
is performed in a wind furnace, the whole 
body of the retort, and that part of the neck 
also which is exposed to heat, must be care- 
fully coated. lo this kind of distillation, 
however, earthen retorts are better adapted ; 
and they may be covered with a composition 
original ly recommended by Mr. Willis, 
Tw’vO ounces of borax are to be dissolved in 
a pint of boiling water, and a sufficient quan- 
tity of slaked lime added to give it the 
thickness of cream. r l his is to be applied 
by a painter’s brush, and allowed to drv. 
Over this a thin paste is afterwards to be 
applied, formed of slaked lime and common 
linseed-oil, well mixed and perfectly plastic. 
In a clay or two, the coating will be suf- 
ficiently dry to allow the use of the retort. 
For joining together the parts of iron 
vessels used in distillation, a mixture of the 
finest China clay, with solution of borax, 
is well adapted. In all cases, the different 
parts of any apparatus made of iron should 
be accurately fitted by boring and grinding, 
and the above lute is to be applied to the 
part which is received info an aperture. 
'Fliis will generally be sufficient without any 
exterior luting ; otherwise the lute of clay, 
sand, and llax, already described, may be 
used. 
In every instance, where a lute or coat- 
ing is applied, it is advisable to allow it to 
dry before the distillation is begun ; and 
even the fat lute, by exposure to the air 
during one or two days after its application, 
is much improved in its quality. The clav 
and sand Jute is perfectly useless, except it 
is previously quite dry. in applying a 
lute, the part immediately over the junc- 
ture should swell outwards' and its diameter 
should be gradually diminished on each side. 
Besides the apparatus already described, 
a variety of -vessels and instruments are ne- 
cessary, having little resemblance to each 
other in the purposes to which they are 
adapted. Glass vessels are required for ef- 
fecting solution, which often requires the 
application ot heat, and sometimes for a 
considerable duration. In the latter case it 
is termed digestion, and the vessel called a 
matt i ass is the most proper for performing 
it. When solution is quickly effected, a 
bottle, with a rounded bottom, may be 
used, or a common Florence-oil flask serves 
thy same purpose extremely well, and be rs 
without cracking, sudden changes of tem- 
perature. Glass rods, of various length, 
and spoons of the same material, or of port 
