25 



so that they will keep their shape. Wlien all is ready, 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 harmless, but too much will 

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

 can be smelled. The time of exposure should be reckoned f-om the lowering of the 

 cyanide ini.o the jars. When the proper time has elapsed, 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 circnlar, 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 

 be emptied into a hole and buried. It is nothing but sulphate of potash, sulphuric 

 acid, and water, having a little hydrocyanic-acid gas in S(jlution. The latter will 

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



K[TMIGATrNf4 BOXES. 



For the purpose of experimenting and where only a few hundred jilants 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 j>lants they 

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

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

 water is 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 quickly 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 sufficiently 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. 



CONDENSED DIRECTIONS. 



(1) Carefully determine the cubic contents of the house and the amount of cyanide 

 of jjotash to use. 



(2) Make the house as tight as possible. 



(8) Arrange so that the ventilators can be opened from the outside. 



(4) Place the jars and strings in position. 



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

 find if they work correctly. 



(6) Hang the bags to one side and put water and acid into the jars; arrange protec- 

 tion and put the bags in place again. 



(7) When all is ready lower the 1)ags into the jars by loosening tlie strings from 

 outside. 



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

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



(9) Next morning bury contents of t lie jars. 



