14 



CIRCULAR 369. U. S s DEPT. OF AGRICULTURE 



gas is given off (fig. 16). The pure gas is colorless, but when mixed 

 with steam produced by the chemical reaction it has the appearance 

 of a light bluish smoke. It has an odor resembling that of peach 

 kernels. 



The dosage is computed on the basis of the quantity of sodium 

 cyanide required. For general mill or factory fumigation where no 

 large quantities of materials are stored, 1 pound of sodium cyanide 



will produce enough 

 gas to fumigate 1,000 

 cubic feet of space, 

 if the building is of 

 reasonably tight con- 

 struction. If the 

 building to be fumi- 

 gated is filled with 

 merchandise, the dos- 

 age required will 

 vary according to 

 the nature of the 

 merchandise. Dos- 

 ages have been com- 

 puted for the fumi- 

 gation of the more 

 important commodi- 

 ties and will be dis- 

 cussed in a later sec- 

 tion of this circular. 



The Geneeator 



For large-scale fu- 

 migations a water- 

 tight 50-gallon wood- 

 en oil barrel (figs. 1, 

 12, and 16) is the 

 most suitable genera- 

 tor to use. Metal 

 barrels are not satis- 

 factory. Barrels in which paint, glue, molasses, pitch, etc., have 

 been stored should be avoided, for when the acid is added it may 

 eat out these materials from between the staves, thus causing a bar- 

 rel thought to be liquid-tight to leak. Barrels should be cleaned and 

 allowed to stand full of water overnight previous to the day of 

 fumigation. Each barrel will hold a maximum charge of 30 pounds 

 of sodium cyanide, or enough to fumigate about 30,000 cubic feet of 

 space. When it is necessary to fumigate small rooms of a few 

 thousand cubic feet as separate units, earthenware or stone crocks 

 (fig. 13) of appropriate size can be used. Oil barrels sawed in half 

 are used less often. 



Each barrel generator should be set in a galvanized-iron washtub 

 in which has been placed a pailful of water containing seA T eral hand- 

 fuls of washing soda. This precaution provides for catching and 



Figure 15. — A good illustration of workmen's indifference 

 to spattering sulphuric acid. Most industrial plants have 

 crews familiar with pouring acid ; yet few are particular 

 to avoid spattering and dropping acid. 



