APPENDIX. 



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 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 win- 

 dows 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. 1 



1 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 conservatories, &c., a series of fans, consisting of boards suspended 

 by two cords with a string at each side. The strings to the right and left are worked 

 through a hole in the doors, or other woodwork. 



