25 



so that they will keep their shape. When all in readj', go out quickly, close the 

 door, and carefully loosen the strings, allowing the bags to settle into the acid. The 

 gas will very soon be given off and fill every portion of the house. It is colorless 

 and smells and tastes like peach pits. A little of it is harndess, y)nt too much will 

 cause death. A small c^uantity will leak out of the house; avoid positions where it 

 can be snielled. The time of exposure should be reckoned f-oni the lowering of the 

 cyanide in^o the jars. "When the proper time has elapsenl, varying for different 

 plants, as previously stated, quickly open the ventilators from the outside, so that the 

 gas can escape as rapidly as possible. It will all be gone from a large house, such as 

 described in this circular, in half or three-quarters of an hour, and the ventilators 

 can then be closed if necessary. Next morning the material left in the jars should 

 l)e emptied into a hole and buried. It is nothing but sulphate of jiotash, sulphuric 

 acid, and Avater, having a little hydrocyanic-aci<l gas in solution. The latter will 

 soon disappear, and the sulplmric acid will unite with lime in the soil, forming gypsum. 



Ft'MIGATIXCi HO.XES. 



For the purpose of experimenting and where only a few hundred plants are to be 

 treated, a tight box may be made of 30 to 50 cubic feet capacity. The box should be 

 as nearly air-tight as possible, with a removable cover and a small door at the bottom 

 for introducing the cyanide of potash into the bowl containing water and sulphuric 

 acid, as shown in fig. 4. 



The wire trays as shown in the same illustration are used in fumigating cuttings of 

 coleus or other plants. When desired the trays can be removed and pot plants set in 

 the box and given such fumigation as desired. To prevent injury to the plants they 

 should be so set that the foliage does not come within 18 inches of the bowl near the 

 small door. When the itlants are arranged the top is put on securely and a little 

 water in poured into the bowl, and then sulphuric acid is added till steam is formed. 

 The necessary amount of cyanide wrapped in a small piece of newspaper is then 

 dropped into the bowl and the little door cjuickly closed. When the desired length 

 of time has elapsed take off the cover and open the door and retire, so as not to 

 breathe the gas. In a few minutes the gas will have sutlieiently escaped so that the 

 plants may be taken out and others treated in the same way. Injury (if there is 

 any) to the plants may not show for two or three days, so in the case of experi- 

 menting, conclusions should not be hastily drawn. The box may be used in the 

 daytime if the work is done in a cool place. For experimental purposes and treat- 

 ing plants on a small scale, a small greenhouse containing 1,000 cubic feet, or less, is 

 better than a box, as the results obtained with it are more reliable, and there is less 

 danger of injury to the foliage. 



CONnENSEI) DIRECTIONS. 



(1) Carefully determine tlie culiic contents of Ihe house and the amount of cyanide 

 of potash to use. 



(2) j\Iake the house as tight as possible. 



(3) Arrange so that the ventilators can be ojiened from the outsi<le. 



(4) Place the jars and strings in position. 



(5) After dark attach the bags containing tlic cyanide to strings, as describeil, and 

 lind if they work correctly. 



(6) Hang the l)ags toonesideand put water and acid into the jars; arrange jirotec- 

 tion and put the bags in plat'e again. 



(7) When all is ready lower the bags into the jars l)y loosening the strings from 



outside. 



(8) After the proper exposure open the ventilators from outside, leaving them 

 open from thirty to forty-five minutes before entering the house. 



(9) Next morning bury contents of the jars. 



