44 COTTON 



(1) Fumigation with hydrogen cyanide is practised 

 in Uganda. A fumigating chamber has been con- 

 structed at Entebbe which is about 8 feet square. 

 It is rendered air-tight by double match-boarding with 

 special paper packed between and is furnished with 

 movable trays for cotton seed. There is a door in 

 the front, and trap-doors are provided in the roof for 

 the escape of the vapour after the fumigation is com- 

 pleted. There are also two small side-doors for the 

 admission' of the fumigating materials after the 

 chamber has been closed. The mixture employed 

 consists of potassium cyanide, sulphuric acid and 

 water. The seed is left in contact with the vapour 

 for two or three hours. 



(2) In the United States of America, fumigation is 

 usually effected by means of carbon disulphide. 

 Experiments which have been made by the Bureau of 

 Entomology have shown that the destruction of 

 insects, and, in particular, the boll-weevil, is more 

 effectually accomplished by carbon disulphide than 

 by hydrogen cyanide. Both these vapours, however, 

 are unable to penetrate a mass of cotton seed com- 

 pletely unless special measures are adopted for their 

 thorough distribution. This is especially the case 

 with fuzzy seeds which tend to cling together very 

 closely. Apparatus has therefore been specially 

 devised which enables a mixture of carbon disulphide 

 vapour and air to be passed through sacks of the seed 

 in such a manner as to reach every part. 



The application of both hydrogen cyanide and 

 carbon disulphide requires the exercise of considerable 

 care as the former is exceedingly poisonous, and the 

 latter is inflammable and liable to cause explosions 

 if carelessly handled. 



(3) The Imperial Department of Agriculture in the 

 West Indies recommends the use of mercuric chloride 

 (corrosive sublimate), and this method is said to have 

 been also adopted in some of the German Colonies. 

 The object aimed at in the West Indies is to prevent 

 the spread of diseases, and particularly fungoid 

 diseases, from one island to another. The solution 

 is made by dissolving one part by weight of mercuric 



