HYDEOCYANIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 5 



the danger of breakage from the heat generated by the process. 

 Deep vessels are more satisfactory for the experiment than the wash- 

 basins often nsed, but the latter are always available and will serve 

 the purpose. Deeper vessels give greater depth to the water and 

 acid and accelerate the chemical action, and there is less danger of 

 spattering. Whenever the room is of such size that much more than 

 3 pounds of cyanid must be employed for it, it is perhaps better to 

 make two charges of half size for such room. 



PROCESS OF rUIMIGATlON. 



In the process of generating the gas the water may be measured 

 in a glass beaker indicating ounces, or for convenience in a pint cup, 

 and poured into the generators. The acid, measured in the same 

 receptacle, is then slowly and gently poured into the water (o avoid 

 splashing or boiling. For all ordinary purposes 1 pint of the acid 

 and 3 pints of water are sufficient for each pound of cyanid. TJie 

 acid should 7iever he placed in the generators first, as advised by 

 some writers, since experience shows that this is dangerous, spatter- 

 ing being almost certain to follow. "Wlien the acid is poured into 

 the water in the jar an ebullition of vapor sometimes arises. Con- 

 siderable heat is also developed by the addition of the acid. 



Wlien the cyanid of potash is finally dropped into the combined 

 acid and water mixture an ebullition or bubbling also takes place 

 similar to that which is produced by a red-hot iron dipped into cold 

 water. Next is given off the hydrocyanic-acid gas, the most poi-. 

 sonous gas in common use. It is colorless and has an odor which has 

 been likened to that of peach kernels. If the fumes are inhaled they 

 are almost certain to prove fatal ; hence the necessitj^ of extreme care 

 and the advisability of two intelligent operators in this work. It is 

 even advisable, especially when the first fumigation is undertaken, 

 that one who has had experience with this method of fumigation be 

 present to give directions. The odor is decidedly metallic, like that 

 produced by striking two pieces of metal together, or of metal against 

 stone. 



The measuring and preparation of the water and acid in the fumi- 

 gating jars should be undertaken in a room with a tile or concrete 

 floor if possible, as the strong acid used is apt to injure wooden floors 

 or carpets should spilling occur. The jars may then be distributed 

 to the different rooms and a bag containing the requisite cyanid 

 placed by the side of each. 



The house is now in readiness to be fumigated. Coats and hats and 

 everything needed outside must be removed, and preferably two per- 

 sons should then go to the top of the house, taking different rooms on 

 the same floor to expedite the process, and place the bags containing 

 the cvanid jjentlv into the vessels to receive them. The chemical 



