58 APPLIED ENTOMOLOGY 



dose. With potassium cyanid the proportions of the materials differ 

 somewhat from this, being 1- part of the cyanid, 1 part of the acid and 

 3 parts of water. 



Granite-ware dishes, without flaws exposing the metal, are excellent 

 containers for this work. They should be considerably larger than are 

 needed to hold the dose, and for large areas it is often desirable to divide 

 this among several containers. First, place the proper amount of water 

 in the container; then add the acid slowly to avoid spattering and the 

 production of too much heat; lastly, drop in the cyanid, which it is desir- 

 able to have loosely wrapped up in tissue paper in order to gain a mo- 

 ment's time in getting out before the gas begins to be given off freely. 



Great care must be taken to leave the place instantly after adding 

 the cyanid to the acid and water, and at the end of the fumigation period 

 there should be a thorough airing for at least a quarter of an hour before 

 entering. If there are windows, these should be opened from the outside 

 only, and under no circumstances should the operator enter too soon. 



