SULPHUR DIOXIDE AS AN IlSrSECTICIDE. 141 



features are large production of gas, the reduction of its temperature 

 to nearly normal, and its control under i^ressure. The sulphur is 

 burned on a grate and also on the floor of the oven as it melts and 

 falls through, and a temperature is developed of from 700° to 1,000° 

 F. To prevent the carrying over of flowers of sulphur the gas gener- 

 ated passes over two " baffle " plates before it reaches the outlet pipe. 

 Through this outlet pipe the gas is carried to a cooler arranged like 

 an ordinary steam boiler tank with numerous pipes around which 

 water is kept constantly circulating. By this means the gas is cooled 

 down to from 70° to 100° F., and is carried thence to the apartment 

 or l^uilding or ship to be disinfected. The gas is forced through this 

 apparatus and into the building to be fumigated b}' means of a blower 

 operated by a small electric motor or by a gasoline engine. There are 

 double gr-ites to the furnace so that the supply of air can be either 

 drawn from out of doors or from the building to be fumigated. In 

 the latter case there is a circulation of air and gas between the appa- 

 ratus and the building, the gas percentage becoming stronger all the 

 time, but without pressure. When the supply of air for the apparatus 

 is taken from without, the air and gas in the building or vessel is 

 under heavy pressure and the penetration of the gas is much in- 

 creased. The gas is tested from time to time by submitting it to 

 water observation in a pipette, and any percentage of gas can be 

 maintained, from a fraction of 1 per cent to 16 per cent or more. 



The special claims made for the gas thus generated are its strong 

 toxic effect on insects, and great penetrating power. The penetra- 

 tion of the gas is both normal to it and very much increased by its 

 being forced into the building under heavy pressure, so that every 

 crevice and crack of the building is filled, and the gas escapes forcibly 

 through every aperture. This apparatus has been tested by a com- 

 mittee of supervising inspectors of steam vessels acting under the 

 authority of the Treasury Department and favorably reported on as 

 a fire extinguisher. The apparatus has also been tested in a limited 

 way by the Public Health and Marine-Hospital Service, and certain 

 of the quarantine officers have been authorized to employ the appa- 

 ratus for the fumigation of vessels under proper conditions. It has 

 also been tested by foreign shipping companies and hygienic labora- 

 tories. 



In the practical carrying out of the details of the experiments, and 

 particularly the supplying of insect material, Messrs. Chittenden and 

 Sanders rendered valuable assistance. The grain and various seeds 

 were furnished by the Office of Seed and Plant Introduction and Dis- 

 tribution of the Bureau of Plant Industry. 



