140 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



that we uiaj' expect to find it in the foliage of trees. The moisture present in 

 the air unites with this sulphur trioxide to form the highly corrosive compound, 

 sulphuric acid, which in its turn acts upon the delicate foliage. 



This same action may occur in the use of sulphur gas for disinfec- 

 tion of dwellings, and for all such uses the important consideration 

 is to have a state of as complete dryness as possible to prevent the 

 formation of sulphuric acid and the consequent bleaching of fabrics 

 and wall papers and the corroding of metallic surfaces. 



Opportunity otfered during the jjast summer and autumn to very 

 thoroughly test the availability of sulphur dioxide and trioxide for 

 various insecticide uses. Many of j^ou probably have heard of Clay- 

 ton gas. This gas is nothing more than the sulphur dioxide and tri- 

 oxide referred to above, and is the same mixture which is obtained 

 bj' burning ordinary stick sulphur or sulphur candles. It was orig- 

 inally employed as a means of extinguishing fires, particularly on 

 shipboard, as in cargoes of cotton or of coal, and the recognition of 

 its value against insects and rodents and other vermin by the com- 

 pany is an outcome merely of its use as a fire extinguisher. This 

 method of disinfection has been very widely exploited by the Clay- 

 ton Company, and has been adopted by the North German Lloyd 

 Steamship Comj^any for use on vessels transporting grain from South 

 America and North American ports to P^urope. It is used not only 

 to destroy insects in cereals, but also to rid steamers of rats and other 

 vermin, and, further, to disinfect vessels in which disease has broken 

 out. The method has received such wide acceptance commercially 

 that it seemed advisable to give it a thorough experimental test. 

 The Clayton Company, furthermore, was anxious to have us make 

 such a test, and was willing to furnish every assistance and meet what- 

 ever expense might be entailed. It being impracticable to conduct 

 a long series of tests in New York, the company sent to Washington 

 an expert in charge of a complete apparatus, which Avas made the 

 subject of a good many experiments, covering a period of two 

 months. These experiments are given in detail below. In explana- 

 tion of the experiments with plants it may be stated that Doctor 

 GalloAvay, of the Bureau of Plant Industry, was consulted, and he 

 deemed it advisable to attempt to use the gas in as nearly a dry con- 

 dition as possible on plants to determine its value, if any, for disin- 

 fecting living plant material. The violent destructive action of this 

 gas on plants is very fully emphasized by these experiments, and it 

 is shown conclusively that probably under no conditions of ordinary 

 practical application can it be used as a means of disinfecting living 

 plants. 



With the Clayton apparatus the gas is prepared by the combustion 

 of common roll brimstone in an oven or generator, and the principal 



