HYDROCYANIC ACID AND MUSEUM SPECIMENS. 67 
escaping. It is advisable to use as a mouth-piece a long tube connected 
by a length of india rubber tubing, so that it is not necessary to put the 
head near the generating bottle. The whole apparatus can easily be 
constructed out of a couple of pickle bottles and a few glass tubes, as 
shown in the sketch at Plate 10, Fig. 1. 
If preferred, the acid may be put into a pipette and allowed to flow 
into the generator by opening a stop-cock or pinch-cock, as the case 
may be. “In this case the top of the pipette should be connected with 
the generator by a bent tube, so as to prevent the acid being blown out 
of the top of the pipette. The object to be kept in view is that the acid 
may be supplied gradually, while any leakage of the gas is prevented. 
An apparatus of this character is shown in Fig. 2. The generator is 
conveniently placed on a shelf fitted to the outside of the back of the 
chamber. 
It has been found by experiments on the various insects infesting 
museum specimens that three ounces of fused cyanide of potassium and 
nine fluid ounces of dilute sulphuric acid, of a strength of two measures 
of water to one of acid, is sufficient to charge this chamber. That is, 
that one quarter of an ounce of cyanide is required for each 10 cubic 
feet of air space. 
The dilute acid should be mixed and cooled before use, otherwise it 
might lead to the breakage of one or both of the bottles. Should this or 
any other accident happen during the evolution of the gas, the safest 
course would be to leave everything for half an hour or so until the gas 
has passed off. Mixing the acid is best done in a bottle or earthenware 
jar stood in a bucket of cold water. It is perhaps best to add the water 
to the acid. 
From two to three hours is sufficient to kill every living thing in the 
chamber, though perhaps it is as well to allow rather more time to elapse, 
particularly w hen large stuffed animals are being treated, as the gas must 
naturally take some time to find its way into ‘the stuffing. When it is 
wished to open the chamber the cover may be released, and by pulling the 
cord it may be raised without going near it. Half an hour should be 
allowed to Bees) for the escape of the gas, before it is emptied of its 
contents. With care there should be no danger in using this apparatus, 
if, as has been said before, it is placed in an open or nearly open shed, if 
the cover is raised by a cord or other means so that it is not necessary 
to approach it closely, and if a sufficient time is suffered to elapse before 
the contents are removed. 
Of its efficacy there can be no question, for moths, spring-tails, 
beetles and their larva are all destroyed, though eggs, and possibly cry- 
salids, may escape. It is doubtful if anything else would be at once so 
simple of application and so cheap. 
Chloroform, bisulphide of carbon, carbonic acid or carbonic oxide 
would probably be equally effective, but the cost and trouble of applying 
would, however, be greater, and the vapours of the two former are 
dange rously explosive when mixed with air, and they are both very diffi- 
cult to keep, even in the best of bottles, in the tropics. 
