6 7 

 APPENDIX A. 



INSTRUCTIONS FOR USING HYDROCYANIC ACID GAS. 



This, the most powerful and dangerous poison used in combating 

 insect pests, should on no account be used by uninstructed or careless 

 people. 



The materials required are a 2 Ib. pot jam-jar, in which place 

 7 ozs. of water, to which add 4 ozs. of sulphuric acid and, as directed 

 below, 2 ozs. of 98 per cent, cyanide of potassium for every 1,000 

 cubic feet of space. 



First make the room to be fumigated as air-tight as possible, 

 leaving one window to open from the outside. Then wrap up the 

 pieces of cyanide in blotting-paper. Having placed in the jam-jar 

 the water and acid, place the jar just within the room to be fumigated, 

 draw the door nearly to, and with the arm reach in and drop the 

 wrapped-up cyanide into the jar, and close the door immediately. Strips 

 of paper well sized should then at once be placed over the crevices. 



The room should remain closed for from two to three hours ; 

 then open the window from the outside, and leave until thoroughly 

 well ventilated. Remember the fumes and the cyanide are deadly 

 poison. Care should be taken that no one remains outside the door 

 of the room as in a passage, as some of the fumes might escape. 



In conservatories, greenhouses, etc., proceed as follows : Add 

 the 4 ozs. of sulphuric acid to the 7 ozs. of water in a jar ; then take 

 the cyanide, which should be wrapped up in a blotting paper, and by 

 means of a stick or piece of string drop it into the water from the 

 outside of the greenhouse. The window or door should then be shut, 

 and the house should remain closed for three-quarters of an hour at 

 least, after which time they can be opened to ventilate, but it should 

 be remembered that it is unsafe to enter the house until an hour or 

 more after the windows and doors have been opened. The best results 

 have been obtained at a temperature of 50 F., about one hour after 

 sunset, when the foliage is dry. 



Mr. G. F. Strawson informs me that he has obtained better results 

 by pouring the diluted acid upon the cyanide of potassium, using no 

 blotting paper. He has also devised and successfully used in con- 

 servatories, &c., a series of fans, consisting of boards suspended by 

 two cords with a string on each side. The strings to the right and 

 left are worked through a hole in the doors, or other woodwork. 



