48 HYDROCYAXIC-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 IX 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 mcomplete. 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 hi 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 
i Gossard, Bui. 67, Fla. Agr. Exp. Sta. 
