48 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



economical and satisfactory proportion of chemicals indicated above. 

 However, since the results of this investigation have been given out 

 the former erratic methods of measuring water have almost entirely 

 disappeared. The usual practice now is to use 3 parts of water 

 which is generally measured in graduated receptacles. The systema- 

 tizing of the use of water has been one of the greatest accomplish- 

 ments of the present investigation. 



In such special treatments as that of nursery stock; mills, houses, 

 and the like, where the extra time required to remove the congealed 

 residue would in no way interfere with the rapid and economical 

 progress of the work, 2 parts (ounces) of water to each part (ounce) 

 of cyanid is recommended. 



THE AMOUNT OF CHEMICALS IN VERY SMALL DOSAGES. 



The results in the fumigation of small trees requiring from 1 to 3 or 

 4 ounces of cyanid have generally been much less satisfactory than for 

 the larger sizes. If the amounts of chemicals used for such small 

 dosages in large generating pots are always in proportion to the 1-1-3 

 formula the reaction will sometimes be slow and incomplete. This is 

 especially the case if pieces of cyanid of such size as to project above 

 the surface of the liquid are used. In order that the cyanid may be 

 entirely covered by the liquid the entire dosage should be not in one 

 piece but preferably in two or more smaller pieces. It is also advis-' 

 able to increase the amount of the acid-water mixture to a slight 

 extent in such cases. An extra ounce of acid and 3 extra ounces 



of water will usually suffice. 



» 



MIXING THE CHEMICALS. 



It is preferable to pour the water into the generator first and then 

 add the acid. The pouring of the water onto the acid is more likely 

 to cause splashing of the acid from the jar onto the fumigator. When 

 the acid and water are in readiness for generating the gas the fumi- 

 gator adds the pieces of cyanid to the mixture and hastily retreats. 

 As already stated, the cyanid should be added while the mixture of 

 water and acid is hot. Other investigators x have called attention 

 to this, while experiments performed by the Bureau of Chemistry of 

 this department show that the reaction with a cool solution is very 

 inferior to one when the heat is great. Potassium cyanid added 

 to the mixture of acid and water when hot lost 10.68 per cent of 

 hydrocyanic-acid gas, while the same cyanid added to a mixture of 

 acid and water while cold lost 23.25 per cent, a difference of more 

 than 12 per cent. The cyanid should never be placed in the water 

 before the acid is added. If the acid is added to the cyanid in solu- 

 tion, a very violent reaction takes place, which will sometimes throw 



1 Gossard, Bui. 67, Fla. Agr. Exp. Sta. 



