(31 



handling the .salt solution, and though CSg is not as poisonous, it is 

 highly explosive. 



For fumigating individual plants the apparatus needed and method 

 of generating the gas was soon ascertained. For small melon and cab- 

 bage plants we had made small paper covers, under which the gas is 

 generated. These are pyramidal in shape, the apex being 8 inches 

 high, and the paper fastened to the inside of a wood frame 3 inches 

 high by 20 inches square, which forms the bottom. This frame is 

 sharply beveled on the lower edge, to enable one to firmly plant the 

 cover in the soil. A good quality of building paper is used for the top 

 and is cut in one piece, so that there is only one seam. The materials 

 for these covers cost from 3 to 4 cents, and we are having fifty made for 

 $6. In the field the covers are easily handled, as they rest one within 

 the other. 



We have found that in using potassium cyanide a small amount in 

 solution is nuich superior to the dr}- salt, it being more easil}^ measured 

 and handled. Furthermore, in first mixing the acid and water and 

 then dropping in the salt much of the heat necessary to the generation 

 of the gas is lost by radiation before the salt can be thrown in, no 

 matter how quickly the generation be performed. By dissolving 

 100 grams of KCn in sufiicient water to bring the solution up to 

 200 cc. , when finished a solution is secured which is of good strength 

 and one of which difierent amounts can be easily computed, 2 cc. 

 equaling 1 gram KCn. To generate the gas a one-fourth dram 

 (S cc.) vial is filled with the KCn solution and an equal or slightly less 

 amount of sulphuric acid placed in the bottom of a 2-dram vial. The 

 larger vial is thrust deep in the earth, being careful to place it so that 

 the overfiowing acid will not strike the plant or cover. The smaller 

 vial holding the cyanide is then dropped into the acid, mouth down, 

 and the plant quickly covered and the cover firmed down. The capil- 

 larity of the one-fourth dram vial prevents a too sudden generation 

 of the gas and allows time for placing the cover. The vials are car- 

 ried in carriers holding one hundred or more, as desired. These are 

 made of a piece of board for the bottoms, in which Iavo hundred holes 

 the size of the vials have been drilled, on the bottom of which a piece 

 of wire netting is tacked. With sides and a hinged cover these make 

 handy and safe trays. No stoppers are used, but a piece of rubber 

 packing inside the cover of the tray would serve the same purpose. 



As regards the amount of cyanide to be used and the length of time 

 necessary to kill plant lice and other inspects, there has not yt't been 

 opportunity for sufiicient tests to give conclusive results. From some 

 75 tests made, we believe that a one-fourth dram vial of the above- 

 mentioned solution (or about four-tenths gram KCn per cubic foot air 

 space) with an equal amount of acid for ten minutes will be found 

 entirely satisfactory. In some tests upon young canteloupes which 



