THE USE OF WATER IN FUMIGATION DOSAGES 



141 



remained, sticking to the generator. When the material dumped upon the 

 ground in piles was examined again, even after several days, the strong odor 

 of hydrocyanic acid gas was easily distinguishable. Old specimens of this ma- 

 terial when analyzed, do not show the presence of any unused cyanide, as a 

 report from the Government Chemist kindly made by Dr. L. O. Howard 

 on some of this very material, would seem to indicate. Yet many days had 

 elapsed between the use of the material in the generators and its analysis by 

 the Chemist. It seems unciuestionable that there is a considerable loss of gas 

 in real practice where severe "frosting" occurs, and when minimum dosages 

 are used as for black scale, it means not only a waste of materials, but a loss 

 in efficiency. Last year one outfit was followed up closely by men from this 

 department and was found not to be killing even the black scale on certain 

 trees with the dosages and times of exposure it was using. The outfit men- 



Fitfure 54. Showing amount of material often dumped out of a single generator 



tioned above, the work of which was seriously impeded by "frosting"' of the 

 generators, was using a formula : water one part, cyanide two parts, acid one 

 and a half parts. In this formula there is evidently not enough water to 

 dissolve and free the potassiuiu sulphate which is formed by the action of the 

 acid on the cyanide, and thus it cakes (Figure 54), retarding the action and 

 ])reventing the most rapid escape of the gas. 



In spite of the importance to be attached to the matter of a proper amount 

 of water in the formula, we know of one outfit which sent a boy through the 

 orchard with a pail and dipper to ladle water into the generators. Such an 

 occurrence is, however, a rarity. All of the outfits whose work I have fol- 

 lowed, have measured out the water with glass graduates (Figure 55), and 

 have shown a disposition to mix the dosages with care, even when the formula 

 u.sed was an unwise one, and the method of estimating the dosage a most 

 uncertain one — as is usually the case in this region. The day of guesswork is, 

 however, rapidly passing. The growers have had enough of it, and are rapidly 



