75 " 

 HYDROCYANIC ACID GAS NOTES. 



By Charles P. Lounsbury and C. W. Mally, Capetown, South Africa. 



The submittal of these notes is prompted bj^ the increasing employ- 

 ment of hydrocyanic acid gas as an insecticidal agent in closed build- 

 ings other than for the destruction of insects accompanying nursery 

 stock. Of late we note recommendations in American rural papers 

 for its use in dwellings to destroy bedbugs, the -strengths mentioned 

 being those ordinaril}^ employed for scale insects. Scale insects, we 

 have found, are exceptionally easy to destroy by the gas, and there- 

 fore our experiences in the treatment of more resistant insects and 

 some miscellaneous tests we have made may have interest to Ameri- 

 can workers. 



The gas has been regularly used during the past two and a half 

 years to effect the destruction of vermin in the sleeping coaches on 

 the various systems of the Cape government railways. With the 

 adoption of this treatment, complaints from bug-bitten passengers, 

 before very frequent, abruptly ceased. On recent inquiry it was 

 ascertained that the railway management remains perfectly satisfied 

 with the measure. Bugs are no longer found, but the coaches are 

 treated once in about four months. Two 1-pound charges of 98 per 

 cent of cyanide are used to a coach and the exi)osure continued from 

 two to four hours according to the length of time available for the 

 work. Two pounds to a coach is about equivalent to an ounce to- 

 every 80 cubic feet. 



Many of the colonial jails swarm with vermin despite many methods 

 employed to mitigate the pest. Carbolic x>reparations, the use of 

 corrosive sublimate in whitewash and as a spray, the burning of sul- 

 phur, and the liberation of sulphurous acid fumes are all reported 

 inefficient. Hydrocyanic acid gas is now coming into use as a last 

 resort. Under our direction several jails have been treated with suc- 

 cess, and it is understood that the government will soon have arrange- 

 ments complete for a regular and systematic fumigation of all the 

 infested premises. The personal condition of the lower-class prisoner 

 on entering is often so indescribably filthy that continual reinfesta- 

 tion must be contended with; hence the expediency of regular appli- 

 cations of the remedy. From 1 pound of cyanide for 1,600 cubic feet 

 to 1 pound for 1,000 cubic feet is used for jail work, the relative- 

 amount being governed to some degree by the extent of unavoidably 

 leakage, the nature of tlie contents that may be harboring the pest, 

 and the season of the year. No trouble is spared to make a space 

 tight; particular attention is paid to the roof and in case this be of 

 corrugated iron, as is common in the colony, the corrugations over fche 

 sills and along the ridge are stopped with plugs of burlap or plugged 

 with clay. The higher the roof the greater is the care exercised in_ 

 making it tight, thus to offset the greater upward draft of air. 



