ITYDROCYAXIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 3 



DIKECTIONS FOR USE. 



Much experience indicates that in order to destroy the household 

 insects mentioned, 1 fluid ounce of commercial sulphuric acid (about 

 1.84 sp. gr., = 66° Baume) diluted with 3 fluid ounces of water, to 

 increase the bulk of the liquid and insure complete chemical action, 

 and 1 ounce of high-grade (98 per cent) cyanid of ]K)tassiuni, must 

 be used for every 100 cubic feet of space. The formula i)er hundred 

 cubic feet, therefore, is as follows : 



Potassium cyanid (98 per cent) avoirdupois ounce__ 1 



Coninierci.il sulphuric acid fluid ounce__ 1 



Water fluid ounces 8 



For loosely constructed frame houses the above amounts may be 

 doubled per hundred cubic feet. The cyanid costs about 40 cents a 

 pound and the sulphuric acid (thick or more sirupy commercial 

 brand) about 4 cents a pound. 



The purity of the cyanid of potash and sulphuric acid to the degi-ee 

 indicated is essential to the success of the fumigation. Potassium 

 cyanid may be obtained in various " technical " grades, ranging be- 

 tween 40 per cent and 98 to 100 per cent actual cyanid, the remainder 

 being an inert salt, usually sodium carbonate or sodium chlorid. which 

 is of no value in fumigation and in the case of sodium chlorid is a 

 jiositive detriment, as this substance, acted upon by sulphuric acid, 

 produces hydrochloric acid, which decomposes the hydrocyanic-acid 

 gas. In cases of extreme adulteration as much as 60 per cent of the 

 fumigant may be decomposed in tliis manner, resulting in inferior 

 effectiveness and tending to tarnish polished metal surfaces exposed 

 to the gas. If chemically pure cyanid is used little tarnishing results. 



Many of the manufacturers of cyanid place on the market a " so- 

 called potassium cyanid '' Avhich consists of sodium cyanid adul- 

 terated with sodium chlorid. The chemically pure sodium cyanid 

 liberates 33 per cent more hydrocyanic-acid gas than does the pure 

 potassium c^^anid, so that to avoid adulterated chemicals it is well 

 to secure the so-called " 133 per cent sodium cyanid " for best results. 

 In the use of this chemical a correspondingly greater amount of the 

 acid is necessary for the complete exhaustion of the cyanid.^ 



Before performing the operation the house must be vacated. It is 

 not necessary to remove any of the furniture or household belongings 

 unless of polished nickel or brass, which may tarnish a little. Liquid 

 or moist foods, as milk, meats, or other larder supplies that are not 

 dry and might absorb the gas, should be removed from the house. iVll 

 fires should be put out ; for while the gas will not biu-n under ordi- 

 nary conditions, it is as well to take no rislvs. 



^ See " The Value of Sodium Cyanid for Fumigation Purposes," by U. R. Woglum (Bui. 

 90, Pt. II, Burejiu of Entomology, 1911). Mr. Woglum's studies of sodium eyanid liave 

 reference especially to its use in the fumigation of citrus orchards. 



