424 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[November 2G, 1870, 
piece, the two pieces thus forming a transverse sec¬ 
tion through the apertures. The two flat surfaces 
which meet together form a perfect joint, the weight 
of the top piece of metal being sufficient to keep it in 
position, so that none of the melted material can run 
between. The working of this mould is compara¬ 
tively easy. Having poured in the substance and 
allowed it to cool sufficiently, it is only necessary to 
lift the to}} piece from the bottom, which brings the 
suppositories with it, then a gentle pressure with the 
thumb easily removes them. From my practice and 
that of others, I find this mould answers extremely 
well, and its simplicity over that of the other wiil 
enable it to be sold much cheaper. 
I will add a few practical remarks on the success¬ 
ful working of the moulds, and the making of suppo¬ 
sitories. Let the moulds be perfectly clean, and as 
cold as possible before using. Whilst pouring in the 
material, stir continually, otherwise the amount of 
active principle will vary in each cone. In dealing 
with tannin, do not use too great a heat, or it w ill 
run together, forming a resin-like mass, which is un¬ 
manageable and useless. Various agents have been 
proposed to assist the removal of the cones, but in 
my experience I have found nothing answer so well 
as the condensation of moisture obtained by breath¬ 
ing into the holes immediately previous to pouring in 
the fluids. If these precautions are neglected, whe¬ 
ther tliis mould be used or any other, failure may be 
the result; it will not, however, be the fault of the 
machine, but of the machinist. In this as in many 
other branches of our profession, it is the skill, dex¬ 
terity and common sense of the manipulator that 
ensures perfect success. 
Caters for Stahnfs. 
CHEMICAL NOTES TO THE PHARMACOPOEIA. 
by william a. tildex, b.sc. loxd. 
DEMONSTRATOR OF PRACTICAL CHEMISTRY TO THE 
PHARMACEUTICAL SOCIETY. 
Alumen. The most interesting process by which 
alum is made, and by which large quantities are 
produced, is that in which ‘ alum schist ’ is the mate¬ 
rial employed. This mineral is a rough silieate of 
alumina, containing iron pyrites, Fe S 2 . By roast- 
ing it, and afteiv ards exposing it to the air, oxygen 
is absorbed, and the mineral effloresces and crum¬ 
bles down to a crystalline mass. This, treated with 
water, gives a solution which contains sulphate of 
aluminum and ferrous sulphate ; concentrated and 
mixed with sulphate or chloride of ammonium it 
gives alum, which crystallizes out, and a salt of 
iron, which is drawn off in the mother-liquors. 
The salt is purified by recrystallization. The alum 
of the Pharmacopoeia is not the only salt known 
under this title. Alum is, in fact, a generic name 
for a class of double sulphates, containing one of 
the univalent metals, and one of those which, like 
aluminum, forms a sesquioxide. They all crystallize 
in octaliedra, and contain the same amount of crys¬ 
tallization-water. 
Ammonia Alum, B.P. (NH 4 ) 2 S0 4 , A1 2 3S0 4 24H 2 0 
Potash Alum .... K 2 S0 4 , A1 2 3S0 4 24H„0 
Chrome Alum . . . . I\ 2 S0 4 , Cr 2 3S0 4 24H 2 0 
Iron Alum.K 2 SQ 4 , Fe 2 3S0 4 24H„0 
Or .(NH 4 ) 2 S0 4 , Fe 2 3S0 4 24H 2 0 
Common alum is soluble in about eighteen tunes 
its weight of cold water, and the solution reddens 
litmus strongly. [§ Its aqueous solution gives, with 
caustic potash or soda, a white precipitate (aluminic 
hydrate, ALoHO) soluble in excess of the reagent, 
and the mixture evolves ammonia, especially when 
heated. The aqueous solution gives an immediate 
precipitate with chloride of barium (this shows it to 
be a sulphate) ; it does not acquire a blue colour from 
the addition of yellow or red prussiate of potash.] 
This last test is intended to indicate that it is free 
from iron; but no ordinary alum is ever met with so 
free from impurity as this would indicate. Traces of 
iron do not interfere with the application of alum to 
ordinary purposes, and probably its complete re¬ 
moval by any practical method would be impossible. 
Dried alum is nearly insoluble in water, but re¬ 
covers its solubility by long boiling. 
Roche alum was originally a native salt (roclie, 
French=rock), but is now -always a factitious sub¬ 
stance, made by stirring up some oxide of iron with 
alum solution whilst crystallizing. 
Ammonias Caebonas.— [§ Produced by submitting 
a mixture of sulphate of ammonia or chloride of 
ammonium and carbonate of lime to sublimation.] 
Ammonia gas is lost in the operation, and the salt 
which condenses in the solid state is of very uncer¬ 
tain composition. The formula given in the Phar¬ 
macopoeia, N 4 H 16 C 3 0 8 , is intended rather to indicate 
the average composition of the commercial salt than 
to set it up as a compound of definite character. 
It appears in crystalline cakes, which are often 
partly made up of a white opaque portion. Tliis is 
less pungent than the translucent parts, and is 
probably chiefly acid carbonate. When treated with 
a small quantity of water, it leaves a residue of acid 
carbonate, and also when exposed to the air it loses 
something to which it owes its pungency, and gives 
the white pulverulent odourless acid carbonate as a 
residue. It is usually from these characters con¬ 
sidered to be a mixture of two salts, one of which is 
almost certainly the acid carbonate NH 4 HC0 3 ; the 
other more volatile and soluble portion is by some 
believed to be the normal carbonate (NH 4 ) 2 C0 3 , by 
others the amnionic carbamate (NH 4 ) NH 2 CO„, or 
(NH 3 ) 2 C0 2 . The latter hypothesis is in accordance 
with the formula of the Pharmacopoeia. The follow¬ 
ing equation would represent the changes by which 
it would be formed :— 
0NH 4 C1 -P 3 Ca CO, 
= 3CaCJ 2 + 3 (NH 4 ) 2 C0 3 . 
Two molecules of the resulting carbonate of am¬ 
monia lose ammonia, and the remainder parts with 
