Ul 
130 REPORT OF THE COMMISSIONER OF AGRICULTURE. , ey & 
to be seen that the less water the cyanide has been dissolved in the less injurious was 
the effect of the gas upon the tree confined in it. The heat generated in the pro- 
duction of the gas is sufficient to vaporize a considerable quantity of the water in 
which the cyanide has been dissolved, and this aqueous vapor collecting upon the 
leaves would condense the gas, which is very soluble in water, forming hydrocyanic 
acid, which is very destructive to plant life. It is also probable that the ascending 
vapor carried with it some of the unchanged cyanide solution, since it was clearly 
apparent that the gas was more injurious to the foliage when generated rapidly than 
when it was produced more slowly. Profiting by this discovery I next tried acting 
with the acid upon the dry, finely pulverized cyanide, and the result proved that the 
gas thus produced was less injurious to the foliage than when generated in the usual 
way. Itstillinjured the leaves to acertain extent, due, as it appears, to the fact that 
the ascending gas carried with it some of the fine particles of the cyanide and lodged — 
them upon the leaves. My next step was to use the cyanide in large pieces instead of 
pulverizing it, and the gas thus produced did not injure the tenderest leaves of orange 
trees, even when confined init for an hour. The proportion of ingredients used was 
about two fluid ounces of sulphuric acid to each ounce of the potassium cyanide. 
Muriatic acid may be used instead of the sulphuric, but it is not as strong, besides 
costing more. Only the best grade of the cyanide, such as that commonly used by 
photographers, can be used for this purpose, since the cold acid will not act upon 
- the poorest grade, which is commonly used for mining purposes; and this remark 
is equally true in regard to both of the processes described below. 
The dry Gas Process.—I have already alluded above to the fact that the drier the 
gas the less injurious was the effect upon the tree confined in it; and it occurred to 
me that the gas might be generated in the usual way, by acting with sulphuric acid 
upon potassium cvanide dissolved in water, and afterward be dried by passing it 
through some medium that would deprive it of its moisture. Knowing the great 
avidity of sulphuric acid for moisture, 1 determined to use it as a drier for the gas, 
and several tests which I have made with this gas dried in this way prove that it 
does not injure the foliage of orange trees confined in it, while it is just as fatal to 
the scale-insects as is the moist gas. The density of the acid through which the gas 
had passed was lowered about one degree, as indicated by the hydrometer; but this 
would not prevent its use for generating the gas. 
The cyanide is dissolved by boiling in water for a few minutes, using 1 gallon of 
water for each 5 pounds of cyanide. Itis desirable to use as little water as possible 
for this purpose, but the quantity could not be very much reduced from that given 
above ; i have tried to dissolve 5 pounds of the cyanide in half a gallon of water, 
but all of the cyanide had not dissolved after half an hour’s boiling. For every 
ounce of the cyanide solution use half an ounce of sulphuric acid, but it is always 
desirable to add some of the acid to the prescribed dose, in order that there may be 
an excessof the acid. No evilresults will follow if double the proper quantity of the 
acid were to be used, whereas if less than the proper quantity were used the whole 
of the gas would not be evolved from the cyanide solution ; hence the advisability 
of always using an excess of the acid. 
In generating the gas the acid should flow upon the cyanide solution in a very 
fine stream. When they come in contact violent action at once takes place, and 
the gas is rapidly given off in the form of a dense whitish fog, resembling smoke 
and possessing a peculiar odor. When this gas, diluted with air, is inhaled, it pro- , 
duces a dryness in the mouth and throat. 
It is impossible to give any definite rule for using the different ingredients that 
will apply to the differently sized trees, owing to the fact that trees of the same 
height may have a varying diameter of top; thus orange trees 12 feet tall ma 
havea diameter of top ranging all the way from 6 to 10 feet. The manner in whic 
the tree is pruned will also make a difference in the quantity of the ingredients to 
be used, some trees being allowed to branch almost from the ground, while others 
are trimmed up from 3 to 5 feet from the ground, 
The following table, based upon numerous experiments which I have made on 
orangé trees under a tent 10 feet tall and having a transverse diameter of 10 feet, 
will give a good idea of the proper quantities of each ingredient to be used in treat- 
ing citrus trees : 
Cyanide Sulphuric 
Height |Diameter| solution | acid 
(in feet). | (in feet). (fluid (fluid 
ounces). | ounces) 
6 5 2 14 
10 10 | 12 i 
12 8 9 5 
16 12 28 16 
20 14 4 26 
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