58 THE ENTOMOLOOIST. 



THE CYANIDE BOTTLE. 

 By J. Aekle. 



In the 'Entomologist' for April, 1893 (xxvi. 136), Mr. P. E. 

 Eaclley, writing from Ceylon, contributes an interesting note on 

 cyanide reaction. The queries put by the writer are, I believe, 

 matters of such general interest that I venture to propose certain 

 solutions, which, although drawn to a large extent from experi- 

 ence, are yet in some measure inseparable from conjecture. 



First, as to the sloppy condition of the cyanide bottle. Mr. 

 Eadley presumes this is attributable to the damp climate of 

 Ceylon. To some extent I believe this likely, but, not knowing 

 his method of charging the bottle, and having no personal 

 acquaintance with the climate of the island, it would be prema- 

 ture to give an unqualified affirmative. I would recommend 

 every entomologist to charge his own bottle, and, in doing so, to 

 remember that he is dealing with one of the most powerful 

 absorbents — plaster of paris. Since its use, in this case, is to 

 fix the potassium in the bottle (through its adhesiveness with 

 glass when mixed with water), and allow the cyanogen to pass 

 through its porous substance, it is important that as little water 

 as possible be added in converting it from a powder into a paste. 

 For a bottle to be carried in the waistcoat pocket (a pomade 

 bottle), break up an ounce of cyanide of potassium ; put it into 

 a bottle. Place on a slate a small heap of plaster of paris ; 

 make a depression in the centre of the heap, and pour into the 

 depression a little water, using the end of a disused table-knife 

 the while to convert the powder into the stiffest paste. Take a 

 little of this paste, and press it with the knife-handle on the 

 potassium, and against the sides of the bottle. Add and press a 

 layer of cotton-wool to receive the insects, and leave the plaster 

 for a few minutes to dry. Then cork with a tight, well-sealed 

 cork, and the bottle is ready for use, its contents being white 

 and dry, or as white and dry as possible. In our climate it will 

 be a long time before such a bottle becomes "sloppy," that is, 

 before the plaster ceases to adhere and becomes mixed with 

 water and loose potassium. As time goes on the collector will 

 note that a dampness, not interfering with efficiency, does some- 

 how affect the contents. Probably this is due to the admissiou 

 of air (never dry) when usiug the bottle, and in a climate like 

 that of Ceylon it may be reasonable to expect this effect intensi- 

 fied. If, however, in mixing the plaster of paris too much water 

 be used, the collector may even start with a sloppy bottle. 



As to its interference with insect colours, cyanide of potassium 

 is one of the most powerful "bleachers" known, and it is difiacult 

 to see how a damp climate can act as a deterrent. On the 

 contrary, dampness may be reckoned as an auxiliary in its 

 attack upon colour. As an entomologist I have never known 



