FUMIGATION OF CITRUS TREES. 
45 
the acid has been diluted with water. With very dilute sulphuric 
acid and up to a strength of 1 part acid to 1 part of water, which is 
as concentrated a mixture as is ever used in fumigation work, nearly- 
pure hydrocyanic-acid gas is given off. By decreasing the propor- 
tion of water used below 1 part, the amount of hydrocyanic-acid 
gas resulting is also decreased until, when concentrated sulphuric 
acid acts on a cyanid, hydrocyanic-acid gas is not given off, but rather 
an entirely different gas called carbon monoxid. 1 
THE EFFECT OF DIFFERENT PROPORTIONS OF WATER. 
On temperature of gas. — Anyone who has watched the escaping gas 
and steam from the reaction of potassium cyanid and sulphuric acid 
wherein different proportions of water were used could not fail to 
notice that the violence with which the generation starts and the 
gas is given off is apparently greatest with the smaller proportions of 
water. Experiments carried on by this investigation showed that 
PR0P0R7WNS OF 
CYANW ACID WATER 
PEP CENT OF GAS G/lfE/V OFF 
10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 
87.84 
93.75 
89.95 
86.25 
81.68 
79.65 
73.47 
43.27 
Fig. 10.— Chart showing total amount of gas evolved when different proportions of water are used. 
(Author's illustration.) 
the temperature of the escaping gas was considerably higher with 
smaller proportions of water than with the larger proportions. In one 
experiment the highest temperature of the escaping gas was 124° F. 
with 1 part of water, but only 90° F. with 8 parts. The temperature 
was approximately uniform with from 1 to 4 parts of water. 
On amount of available gas . — The Bureau of Chemistry of this 
department, at the request of the Bureau of Entomology, performed 
an experiment to determine the amount of hydrocyanic-acid gas 
available when generated with proportions of water varying from 1 
to 8 parts. The results have been incorporated in the accompanying 
chart (fig. 10). 
In these experiments commercial sulphuric acid 66° Baume, analyz- 
ing 92.77 per cent pure, and potassium cyanid 97.12 per cent pure 
were used. Three ounces (fluid) of sulphuric acid and 3 ounces 
i See Part III of this Bulletin. 
