New YoiiK Agricultural ExrERiMExx Station. 329 



The amount of cijanide to use. — 'The amoimt of cyanide to use 

 depends upon the strength required and the size of the tent or 

 box. For fumigating orchard trees in winter use 0.3 gram of 

 cyanide per cubic foot of space inside the tent or box. For 

 example, suppose a tree is to be fumigated wnth the box fumi- 

 gator described in our Bulletin No. 181. This fumigator meas- 

 ures 10x6x6 feet. It contains, therefore, 360 cubic feet. We 

 wish to use the gas at a strength of 0.3 gram of cyanide per 

 cubic foot. The amount of cyanide required would then be 

 360x0.3=108.0 gram.s3 or 3.51 oz. 



After reducing to ounces use one and one-half times as many 

 fluid ounces of sulphuric acid as cyanide, and one and one-half 

 time as much water as acid. This would make the formula for 

 fumigating a tree in a 10x6x6 ft. fumigator with gas containing 

 0.3 gram of cyanide per cubic foot as follows: 



Cyanide of potassium 98-99^ pure 3.51 oz. avoir. 



Sulphuric acid 5 . 27 fl. oz. 



Water 7.90 " 



The exact amount of acid is not important. A small fraction 

 of an ounce will make no difference. In this case 5 oz. would 

 answer the purpose or if preferred o^ oz. could be used. Like- 

 wise eight ounces of water could be used in place of 7.9 ounces. 

 The water should first be placed in the generating dish, which 

 should be a flat-bottomed, open dish, preferably earthenware, the 

 acid being added slowly. "V\Tien all is ready, drop the cyanide 

 into the dish. A very convenient way to handle the cyanide is 

 to measure it out in small Manila paper bags and when ready 

 to set off the charge drop the bag with the cyanide into the acid. 



Cyanide of potassium can usually be had for about 33 cts. a 

 pound and commercial sulphuric acid by the carboy (about 12 gal- 

 lons) at 1^ cts. a pound. At these prices the cost of the chem- 

 icals to fill the above fumigator with gas containing 0.3 gram of 

 cyanide per cubic foot would be about 7^ cts. 



'One gram is equivalent to .03257 oz. avoirdupois. 



