66 HYDROCYANIC ACID AND MUSEUM SPECIMENS. 
suggested the application of the gas to the insect pests which attack 
natural history specimens in museums, and as the experiment has proved 
completely successful some account of it may be of interest. 
As applied to trees, a tent of waterproof material is erected over 
them and the gas is generated in an open vessel placed on the ground 
beneath the tent. Half an hour is said to be sufficient to kill all the scale 
insects on a tree, but the gas so applied has not a fatal effect on mites 
and beetles. As beetles of several kinds are the worst enemies of 
museum specimens, it was necessary to medily the process, by using an 
air-tight box in which to place the specimens and subject them to 
the gaseous poison, and also to increase the amount of the gas in propor- 
tion to the volume of the enclosed air. 
The death chamber may be made in almost any way, so long as the 
requirements of the case are fulfilled. These are that it should be large 
enough to accommodate any specimen in the collection, that it can 
be closed air-tight, that it can be opened without danger to the person 
using it, and that it is fitted with moveable shelves so as to take nume- 
rous small specimens at one time. The best material to build it of would 
be brick, with an inside rendering of cement. The death chamber 
recently built at the Perak Museum is a large wooden box, measuring 
8 feet long by 6 feet high by 2} feet wide. It is rendered air-tight 
by pasting strips of paper over all the seams and then serving the whole 
interior with several coats of white paint. One entire side is moveable. 
This is hung from the top edge by jointed hinges and can be raised by a 
cord attached to its lower edge and passed over a pulley in the roof of 
the building. ‘The cover is held in place by eight wedges, which are 
driven in between it and four vertical moveable wooden bars which 
fit into holes in eight pieces of wood which project from the top and 
bottom of the chamber. The edges of the case are covered with list, so 
that a tight joint can be made. At the two ends of the chamber are three 
horizontal pieces of wood which serve to support three moveable shelves, 
each of which is composed of four wooden bars. This chamber contains 
120 cubic feet, and will hold a large number of specimens at one time. 
It is placed in a shed where there is free ventilation, a matter of 
importance, as otherwise there might be danger of inhaling the gas 
when the chamber was opened, with unpleasant or even serious results. 
The hydrocyanic, or as it is more commonly called, prussic acid gas, 
is produced by decomposing cyanide of potassium with sulphuric acid. 
The common form of sulphuretted hydrogen gas bottle is a satisfactory 
apparatus to use. The long glass funnel in the large bottle is to be re- 
placed by a wide glass tube, this should not descend far into the bottle ; 
it is to be bent at ‘right angles and serves to carry the gas into the death 
chamber. To use the apparatus, put into the larger bottle the coarsely 
pounded cyanide and into the smaller the dilute. sulphuric acid, replace 
the corks and tubes, then blow into the smaller bottle by the free tube 
and force some of the acid through the connecting pipe into the larger 
bottle containing the cyanide. The evolution of the gas will at once 
begin, and, as required more acid is forced over until the whole of the 
cyanide is decomposed. There should always be more acid in the small 
bottle than is required, so that what is left in it will prevent the gas from 
