69 



was given to this office, and a stronger test was recommended, three 

 times the usual strength — that is, 3 ounces of cyanide of potash to 

 100 cubic feet of space — and a longer exposure. This was applied 

 September 28, and renewal Avas made the following day, twenty- 

 three hours later, arrangements having been made so that jars con- 

 taining fresh acid could be introduced and charged with cyanide 

 through a window. The second exposure lasted nineteen hours, or 

 practically forty-two hours in all. 



Prior to experiment it was ascertained that the insects had been 

 breeding in the lower covering of the chairs. Dozens of larvoe were 

 found between the covering and the webbing Avhich was nailed across 

 the latter. 



After airing the infested room hundreds of larvse were observed 

 that had fallen from the lower covering of chairs (which had pre- 

 viously been ripped otf to facilitate the effect of the gas) to the floor, 

 and all adults observed were dead, as were also house flies. Some of 

 the larvse and beetles which had been subjected to treatment were 

 placed in a vial to determine the effect of the experiment. They all 

 died, but considerably later it was found necessary to dispose of the 

 chairs, as they were still infested. 



Owing to the failure of our first experiment with hydrocyanic-acid 

 gas against the cigarette beetle, as also of another experiment on the 

 confused flour beetle {Triholhnn confusmn Duv.), it was suspected 

 that something might be wrong with the ingredients, and accordingly 

 a sample of cyanide of potash was selected at random and submitted 

 to Mr. J. K. Haywood, of the Bureau of Chemistry, for analysis. He 

 reported that it contained 37.18 per cent cj^anogen, 0.57 per cent 

 chlorine, and the remainder a mixture of potassium and sodium, the 

 analysis showing that this sample was not the product paid for; in 

 other words, not 98 per cent potassium cyanide, but a mixture of 

 potassium cyanide, sodium cyanide, and sodium chloride. The three 

 compounds were present in such proportions that the mixture yielded 

 93 per cent of the amount of hydrocyanic-acid gas it should yield if 

 the sample were pure potassium cyanide, and yet the amount of cyan- 

 ogen which might be produced b}'^ this mixture could be 53 per cent, 

 whereas in pure potassium cyanide it is 40 per cent. 



In the second test against this species the potassium cyanide was 

 used three times as strong as in the first. In the meantime, a sample 

 was being analyzed by Mr. J. K. Haywood. His results were as 

 follows : 



I'er cent. 



Potassium cyanide 'A. 70 



Sodium cyanide 2. 07 



Sodium clilovide 3.89 



Potassium carlionate 39. 28 



Other impurities 2. 70 



Moisture 0.30 



