9G8 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[Jane 3, 1S71 
tion or deoxidation of the red oxide with, formation 
of the black mercurous oxide. This is not so liable 
to occur when, as in the present Pharmacopoeia, 
yellow wax is employed. In the last edition the 
ointment was prepared from white wax, prepared 
lard and almond oil. So made, it rapidly becomes 
grey, and, if a careless operator has used unwashed 
lard, it even becomes white from the reaction of the 
salt upon the mercuric oxide to form corrosive sub¬ 
limate. 
Hyduaugyiii Pehchloridum. 
A mixture of mercuric sulphate, common salt and 
a little black oxide of manganese is heated in a dry 
flask, or any suitable subliming apparatus. The per- 
chloride condenses in distinct brilliant prismatic 
crystals or in masses. The change which occurs is 
a double decomposition. 
HgS0 4 -f 2Nad = HgCl 2 + Na 2 S0 4 . 
But since the sulphate of mercury is apt sometimes 
to contain small quantities of mercurous sulphate, 
which by reacting upon the salt would give rise to 
calomel, the oxide of manganese is added to prevent 
this. 
[§ Perchloride of mercury is more soluble in al¬ 
cohol, and still more so in ether than in water.] 
When dissolved in much water and exposed to light, 
a partial decomposition of the salt ensues, and a 
little calomel is deposited. In the Liquor Hyclrarg. 
Bichlor. B. P., a small quantity of sal-ammoniac is 
added, with the view of preventing this change by 
forming with the perchloride a more stable double 
salt. 
The aqueous solution is acid to test-paper. 
[§ Its aqueous solution gives a yellow precipitate 
with caustic potash (HgO), a white precipitate 
(HgNH 2 Cl) with ammonia, and a curdy white pre¬ 
cipitate (Ag Cl) with nitrate of silver. When heated 
it sublimes without decomposing or leaving any 
residue.] 
Specific gravity of vapour 
200 + 2(3^m) x . 0G93 _ 9 . 39> 
The antidote to corrosive sublimate is albumen, 
which combines with it to form an insoluble com¬ 
pound. The white of egg should be given in mode¬ 
rate quantities, or the insoluble compound is redis¬ 
solved. 
ECONOMIC ENTOMOLOGY. 
In the collection of economic entomology exhibited at 
South Kensington Museum, the life history of the in¬ 
sects is given, not only by specimens showing them in 
their various stages of development, but also by exhibit¬ 
ing specimens of the material subject to attack, with the 
insect belonging to it fixed in the natural position, as 
observed either when carrying on its work or under¬ 
going its transformations. 
_ Thus, in the case of our timber beetles, specimens are 
given showing the injured wood with the beetles at work 
on it as when alive, and in the case of some of our 
insects which carry on their work or transformations in 
the earth, specimens are given of the earth structures, 
so preserved as to present them, if not in their full 
freshness, at least sufficiently clearly for purposes of in¬ 
struction. 
For the method of preparation of the earth-cells we 
may take those of the Balaninus glandium as an example. 
The cells should be laid on a smooth surface, such as 
wood or china, and a rather thin solution of gum arabic, 
carefully dropped from a camel's-hair pencil, on all the 
parts that can be reached, and the moisture allowed to 
soak in; the drops of gum-water may be gently drawn 
in any direction required with the point of the brush, 
hut the earth should not on any account he touched with 
the brush during the process, or it will he reduced to 
mud, and the characteristic markings destroyed. When 
dry the specimen should be turned, and the gum-water 
applied as before to the parts previously untouched, and 
the process repeated till the specimen is firmly set. If 
the operation has been carefully performed, the glaze on 
the surface will give little more than the appearance of 
wet earth; but if this is objectionable a little dry earth 
of the same kind, powdered over the surface whilst still 
damp, will restore the natural appearance. 
Such specimens as ants’ nests may bo preserved by 
taking up a section of a few inches in thickness very 
carefully with a sharp spade, or, better still, with a long 
kitchen-knife, and laying it at once on a board, with the 
face, afterwards to be exhibited, downwards ; and, hav¬ 
ing trimmed the specimen neatly, so as to be square at 
the sides, enclosing it in a strong cardboard or thin 
wooden frame (like a box without top or bottom), filling 
in what is then the upper side with very liquid plaster 
of Paris up to the edge of the enclosing frame. The 
liquid mixture will run into the holes, and, setting 
almost immediately, will keep the earth from falling 
away when the specimen is restored to its proper posi¬ 
tion, and the surface to be exhibited may then, if neces¬ 
sary, be treated as above described, with gum-water to 
secure the safe preservation of the earth galleries. 
Beetles injurious to timber may be well displayed by 
choosing a piece of wood with characteristic specimens 
of the injuries caused by the kind of beetle to be exhi¬ 
bited, and drilling two small holes beneath the spot 
where it is to be placed, then passing a fine wire hori¬ 
zontally through the thorax of* the insect, drawing the 
two ends through the drilled holes, and tying them 
securely at the back of the wood. If a pin is also passed 
through the beetle in the usual way, it will help to 
secure the insect in the desired position; and the head 
of the pin may he cut off or concealed by a touch of 
paint, so as not to spoil the life-like appearance of the 
specimen. Beetles, or other insects too small or soft in 
their texture to be treated in this manner, may be fixed 
by gum, glue or marine glue, of a single pin may bo 
driven through so deeply into the wood that the head of 
the pin rests on the insect, and sometimes by carefully 
lifting one of the elytra of a beetle, the pin may be 
passed through beneath it, and the wing-cover return¬ 
ing to its place will entirely conceal the artificial sup¬ 
port. 
Rupee may be fixed with glue and concealed pins, and 
the larger larvae, such as those of the goat-moth, may 
be well represented by plaster models from life, fixed in 
the injured timber from which the original was taken : 
but in all these matters the characteristic position and 
colouring of the insect should be well studied before any 
attempt is made to represent it, and all artificial attach¬ 
ments or supports should show as little as possible. If 
it is quite unavoidable that they should appear, a little 
earth or wood-dust applied to the surface of the glue or 
gum, and a few touches of paint on the wires will 
usually deaden them, so as to attract little notice. 
Besides the substances mentioned, there are others 
still more perishable, such as fruit, leaves or roots, 
which it is necessary should be represented, in order to 
give perfect illustration of the destructive powers of 
many of our insects. In some cases these can be shown 
by accurate drawings; in others, models in wax or 
plaster give a satisfactory representation, and in the 
Entomological Collection of the Horticultural Society at 
South Kensington are many specimens of models in 
plaster of Paris, representing vegetable substances in¬ 
jured by insects, the insects themselves in their larval 
