CHEMISTRY OF FUMIGATION. 
101 
of the cyanid, previously dissolved in 10 cc of water, and partially 
open the stopcock, allowing the solution of the cyanid to flow slowly 
into the acid. As soon as the stream of hydrocyanic-acid gas reaches 
"B," containing the potassium hydrate, it is absorbed very readily; 
in fact, so readily that unless the flow is quite rapid the potassium- 
hydrate solution rises in the tube and in several instances was drawn 
back into flask ' l A." In order to prevent this it is necessary to watch 
the apparatus constantly and not permit the flow of gas to subside; 
or, if this is impossible, to close the pinchcock on the tube connecting 
the two flasks for an instant and apply suction. As soon as the solu- 
tion of the cyanid has all been added the separatory funnel is washed 
down with 1 cc of water, heat is applied to flask "A," and the tem- 
perature of the acid brought to 110° C, which is about the average 
temperature obtained by adding 1 part acid to 2 parts water. The 
heat is then removed, flask "F" attached, suction applied, and air 
drawn through the apparatus for about 40 minutes. According to 
the authorities, air alone drawn through a solution of a cyanid 
causes it to decompose, but this action is very slow and for this work 
can be neglected. The residue in "A" is washed out into a beaker, 
cooled, made alkaline with potassium hydrate, and the amount of 
cyanid present determined by titration with tenth-normal silver 
nitrate. The solution in "B " is washed out into'a 500 cc flask, made 
to the mark, and aliquot portions used for the determination of the 
cyanid present. Solutions in "C" and "D" were also tested for 
c} r anid, but in only two or three instances was any present, as in most 
cases it had all been absorbed in "B. " 
RESULTS OF EXPERIMENTS. 
The results of the experiments conducted as outlined, when employ- 
ing pure chemicals, are given in the following table : 
Results of experimental work. 
Experiment No.— 
Equivalent 
of HCN in 
the sam- 
ple. 
Per cent of 
total HCN 
evolved. 
Per cent of 
total HCN 
remaining 
in "A." 
Per cent of 
total HCN 
decom- 
posed (by 
difference). 
1 
Per cent. 
51.82 
51.82 
51.82 
51.82 
51.82 
94.81 
94. 40 
93.77 
96.90 
96.28 
3^29 
3.84 
2.20 
1.40 
1 60 
2 
2 31 
3. 
2 39 
4 
90 
5 
2 32 
Average 
51.82 
95.23 
2.86 
1 91 
These results indicate that there is some variation in the amount 
of hydrocyanic acid decomposed, but this would be expected from 
the fact that the experiments are subject to slight variations in the 
