VIII, D, 1 Jones: The Cigarette Beetle 19 



more than one generation is used for a given space, care must 

 be taken to have the chemicals proportionately distributed be- 

 tween the generators. Under no circumstances should a person 

 be in the compartment when evolution of this gas commences. 

 The cyanide should be added to the sulphuric acid and water 

 from the outside. This can be done easily by placing the cyanide 

 in a paper bag and lowering it into each generator by means 

 of strings which pass through screw eyes at the top of the com- 

 partment. Each string should be arranged so that one end 

 hangs directly over the generating vessel and the other passes 

 out through a small hole at the side of the door. After lowering 

 the cyanide into the generator, the hole through which the strings 

 pass must be closed to prevent the escape of the gas. 



After exposing the tobacco to the fumes of this gas for a 

 period of at least twenty-four hours, the compartment may be 

 opened. The operator should hold his breath while opening 

 the door, and should retreat immediately out of reach of the 

 fumes. About fifteen minutes are sufficient to allow the fumes 

 to pass away, provided a current of air can be directed into 

 the compartment, otherwise a half -hour is not too long to wait 

 before entering. 



A poisonous bluish residue will be left in the generators and 

 should be disposed of immediately by pouring it into holes in 

 the ground and covering with earth or emptying it into the 

 sewer trap and flushing for some time. 



PRECAUTIONS 



Hydrocyanic-acid gas is a most deadly poison, and there is 

 no antidote. Do not inhale any of it. The potassium cyanide 

 and sulphuric acid used for the production of hydrocyanic-acid 

 gas are both poisonous and must be handled Avith due precaution. 

 If the following points are carefully observed, there need be no 

 danger from the use of these substances. 



1. Always keep the sulphuric acid in glass-stoppered bottles, and take 

 care not to get the acid on the skin or on the clothing, as it produces 

 serious burns. 



2. Potassium cyanide should never be handled with the bare hands, as 

 small pieces might get under the finger nails, be transferred to the mouth, 

 and produce cyanide poisoning. Gloves or wooden pincers are convenient 

 for working with cyanide. Potassium cyanide should be kept in tightly 

 covered vessels as otherwise it deteriorates rapidly. 



3. Never reverse the order of mixing the chemicals. Always pour the 



