SULPHUR DIOXIDE AS AN INSECTICIDE. 147 



in the small bags at the bottom were unaffected. (See Experiment 



No. 11.) 



Experiment No. 10. 



Designed to test the possibility of using the gas for the iumi- 

 gation of ships loaded with bananas. A bunch of green bananas was 

 submitted to 6 per cent gas without pressure from 3 p. m. to 10 a. m., 

 a total of some 19 hours. There was still 6 per cent gas found in the 

 building an hour after disconnecting the apparatus, and practically 

 the same amount 2 hours after. After 6 hours the percentage had 

 fallen to 5 per cent, and at the end of the experiment there was 

 apparently somewhat less than 1 per cent in the building.* 



Results. — The bananas, which could be observed through the win- 

 dow, showed no bleaching effect for the first 5 or 6 hours, but the next 

 morning were much bleached and yellowed and apparently somewhat 

 softened, the fruit having in the meantime become moist from con- 

 densed moisture, which undoubtedly occasioned the bleaching noted. 

 The indications are that, in view of the natural moisture which would 

 be found in holds of banana-laden vessels, the use of this gas for 

 fumigation would be rather disastrous to the appearance and quality 

 of the fruit. 



Experiment No. 11. 



This experiment duplicated experiment No. 8, except for the 

 strength of gas, and was designed to determine the penetration 

 powers of a high percentage of gas rather than a low percentage, 

 which had proven ineffective. The conditions were the same as in 

 experiment No. 8. The generator was started at 4.10 p. m. By 4.30 

 a 5 per cent gas was being generated, and the gas was forced into the 

 building under pressure at 4.40. By 5 p. m. 10 per cent gas was 

 reached in the building, 12 per cent at the machine. By 5.45 p. m. 

 15 per cent of the gas was secured in the building, and this percentage 

 was kept up under pressure until 6 p. m., when the generation of gas 

 was stopped. The gas was therefore under pressure in the building 

 about 1 hour and 20 minutes, and the total operation of the machine 

 was 1 hour and 50 minutes. The gas in the building was tested at 

 7.50 p. m., and 10 per cent found at that time. At 9.50 in the morn- 

 ing, the following day, 5 per cent of the gas still remained in the 

 building. The building was then opened and aired and the infested 

 grain removed from the bottom of the jars and from the zinc-lined 

 box. It was evident, from the odor, that the gas had penetrated to 

 the bottom of both of these receptacles, and an examination of the 

 infested grain showed the insects all apparently dead. 



a The retaining capacity of the building for the gas varied slightly with the 

 condition of the external air, falling more quickly in windy weather than in 

 still weather. 



