PROPORTION OF WATER AND ACID. 25 



CHEMICALS. 

 DEGREE OF PURITY REQUIRED. 



The materials used in generating hydrocyanic-acid gas are potas- 

 sium cyanid (KCN), sulphuric acid (H2SO4), and water. The cyanid 

 and acid should be purchased of a reliable dealer. The cyanid should 

 be guaranteed to be 98 or 99 per cent, which is practically chemically 

 pure. The acid should be guaranteed to be 66° "- and, as additional 

 assurance, it would be well to have a sample tested by a druggist or 

 by the fumigator himself by using an acid hydrometer. This instru- 

 ment is inexpensive and can be obtained through any druggist. 

 A firm or hard cyanid should be obtained rather than a soft or 

 porous product. 



HANDLING, AND NECESSITY FOR PROTECTION FROM MOISTURE. 



Potassium cyanid can be purchased in boxes of 200 pounds each. 

 The C3''anid readily absorbs moisture, and for this reason after a box 

 is opened it should be kept constantl}^ covered with burlap sacks and 

 protected against rain when necessary. When only a few trees are 

 to be treated and the box of cyanid is not to be completely used, 

 within a few days at the most, it is recommended that it be stored 

 in large-sized tin cans with covers made practically air-tight by means 

 of cheese cloth or muslin. The acid when used in large quantities is 

 purchased in drums containing about 1,500 pounds. In smaller quan- 

 tities it is sold in carboys containing a little less than 200 pounds. 

 The carboys make convenient receptacles for handling in the groves. 

 In emptying from a drum into carboys a large funnel of glass or 

 sheet lead is useful. Wlien the carboys are boxed and not other- 

 wise provided with handles, strips of wood may be nailed along paral- 

 lel sides projecting at each end, so as to make convenient handles 

 for two men. If carboys can not be obtained or the quantity of acid 

 used does not require temporary containers for such amounts, large 

 jugs may be used. In all cases the containers, except when in use, 

 should be stoppered. For this purpose wooden plugs, made tight 

 with asbestos, such as can be bought in sheets from hardware dealers, 

 may be used. Wlien the acid is to be stored in carboys for more 

 than a few days the plugs should be made extra tight by means of 

 plaster of Paris. For water required in the generation of the gas 

 anything that is reasonably clean will answer the requirements. 



PROPORTION OF WATER AND ACID. 



The proportion of the materials theoretically required for a complete 

 chemical reaction is 1 part of potassium cyanid, 1 part of acid, and 2 

 parts of water. In practice, however, an excess of acid up to one-fourth 



« Sixty-six degrees sulphuric acid is 93 per cent strength. 



