PHARMACY. 
tnres, bnt they become so hard that they 
can scarcely be removed, and often harden 
so quickly after they are mixed u|>, that 
they must be applied immediately. Exam- 
ples ; 
Quick lime well incorporated with a sixth 
part of muriate of soda. 
Burnt gypsum, made up with water. 
One ounce of borax dissolved in a pound 
of boiling water, mixed with a sufficient 
quantity of powdered clay. Mr. Watts’s 
fire lute. 
One part of clay with four of sand formed 
into a paste with water. This is also used 
for coating glass vessels, in order to render 
them stronger and capable of resisting vio- 
lent degrees of heat. It is then made into 
a very thin mass, and applied in successive 
layers, taking care that each coat be per- 
fectly dry before another be laid on. 
The lutes for lining furnaces will he de- 
scribed when treating of furnaces. 
The junctures of vessels which are to be 
luted to each other, must previously be ac- 
curately and firmly fitted, by introducing 
between them, when necessary, short bits 
of wood or cork, or, if the disproportion 
be very great, by means of a cork fitted to 
the one vessel, having a circular hole bored 
through it, through which the neck of the 
other vessel or tube passes. After being 
thus fitted, the lute is either applied very 
thin, by spreading it on slips of linen or 
paper, and securing it with thread, or, if it 
is a paste lute, it is formed into small cylin- 
ders, which are successively applied to the 
junctures, taking care that each piece be 
made to adhere liritdy and perfectly close 
in every part, before another is put on. 
Lastly, the whole is secured by slips of linen 
or bladder. In many cases, to permit the 
escape of elastic vapours, a small hole is 
made through the lute with a pin, or the 
lute is perforated by a small quill, fitted 
with a stopper. 
Heat and Fuel. As caloric is an agent 
of the most extensive utility in the chemi- 
cal operations of pharmacy, it is necessary 
that we should be acquainted with the 
means of employing it in the most econo- 
mical and efficient manner. The rays of 
the sun are used in the drying of many ve- 
getable substances, and the only attentions 
necessary are to expose as large a surface 
as possible, and to turn them frequently, 
that every part may be dried alike. Tiiey 
are also sometimes used for promoting spon- 
taneous evaporation. 
The combustion of different substances 
is a much more powerful and certain source 
of heat. The substances employed for this 
purpose, are either fluid or solid. Alcohol, 
oil, tallow, wood, turf, coal, charcoal, and 
coke, are all occasionally employed. Alco- 
hol, oil, and melted tallow, fluid inflamma- 
bles, must be burnt on porous wicks. These 
act merely mechanically, by drawing up a 
portion of the fluid to be volatilized and in- 
flamed. They are therefore burnt in lamps 
of various constructions. But although 
commonly used to jtroduce light, they af- 
ford a very uniform, though not very high 
temperature: it may, however, be increased 
by increasing the number of the wicks, and 
their size. Alcohol produces a steady heat, 
no soot, and, if strong, leaves no residuum. 
Oil gives a higher temperature, but on a 
common wick produces much smoke and 
soot. These are diminished, and the light 
and heat increased, by making the surface 
of the flame bear a large proportion to the 
centre, which is best done by a cylindrical 
wick, so contrived that the air has free ac- 
cess both to the outside and to the inside of 
the cylinder, as in Argand’s lamp, invented 
by Mr. Boidfon of Birmingham. In this 
waj-^ oil may be made to produce a consi- 
derable temperature, of great uniformity, 
and without the inconvenience of smoke. 
Wicks have the inconvenience of being 
charred by the high temperature to which 
they are subjected, and of becoming so 
clogged as to prevent the fluid from rising 
in them : they must then be trimmed, but 
this is seldomer necessary with alcohol and 
fine oils than with the coarser oils. Lamps 
are also improved by adding a chimney to 
them : it must admit the free access of air 
to the flame, and then it increases the cur- 
rent, confines the heat, and steadies the 
flame. The intensity of the temperature of 
flame may be increased astonishingly, by 
forcing a small current of hot air through it 
as by the blow-pipe. Wood, turf, coal, 
charcoal, and coke, solid combustibles, are 
burnt in grates and furnaces. ATood has 
the advantage of kindling readily, but af- 
fords a very unsteady temperature, is in- 
convenient from its flame, smoke, and soot, 
and requires much attention. The heavy 
and dense woods give the greatest heat, 
burn longest, and leave a dense charcoal. 
Dry turf gives a steady heat, and does not 
require so much attention as wood ; but it 
consumes fast, its smoke is copious and pe- 
netrating, and the erapyreumatic smell 
which it imparts to every thing it comes in 
contact with, adheres with great obstinacy. 
