46 HYDROCYAXIOACID GAS FUMIGATION IX CALIFORNIA. 
(avoirdupois) of potassium cyanid were employed in each experi- 
ment, and 3, 6, 9, 12, 15, 18, 21, and 24 ounces, respectively, of 
water were used in the different experiments. 
From this chart it is evident that with the grades of acid and 
cyanid mentioned the largest amount of gas is available from 2 parts 
of water. As the proportion of water is increased above 2 parts the 
available gas is decreased, until with 8 parts of water we obtain only 
about 43 per cent of gas, or less than one-half as much as with 2 
parts. In other words, 1 ounce of cyanid and 1 ounce of acid in 
combination with 2 ounces of water will produce much more avail- 
able gas than 2 ounces of c} r anid and 2 ounces of acid with 16 ounces 
of water. 
The cause for the smaller amount of gas with 1 part of water has 
been explained on page 44. One of the principal reasons for the 
decrease of the amount of gas as we go above 2 parts of water is that 
the temperature of the acid-water mixture decreases as the pro- 
portion of water increases. With dosages of 5 ounces of cyanid the 
temperature was found to be 190° F. where two parts of water were 
used, but only 125° F. with 8 parts of water. The hotter the acid- 
water mixture the quicker and more violent the reaction with the 
cyanid will be. Secondly, hydrocyanic-acid gas is very soluble in 
water. As the cyanid is immersed during the reaction, the gas has 
to rise through the liquid in order to escape. Less gas will be 
absorbed by rapid evolution through a small amount of water than 
by slower rise through a large amount . 
The proportion of water used by different fumigators under the old 
system has varied all the way from 2 to 8 parts, some men even 
varying widely in their individual work. In brief, the method fol- 
lowed by the "generator" man in dosing has been that on coming to 
a tree he first looks at his can of cyanid for that tree and then makes 
a guess as to how many ounces it contains. If he is using 2 parts of 
water he will use twice the amount that he thinks there is cyanid in 
the can; if 8 parts, then 8 times the amount of cyanid he thinks 
there is in the can. A very few outfits have measured the water in 
graduated beakers; the majority of receptacles used have varied all 
the way from half-pint dippers to quart dippers, quart pitchers, or 
even old tin cans. Think of measuring with accuracy the amount of 
water for a tree requiring 4 ounces of cyanid with a quart pitcher! 
The writer has frequently seen fumigators, in measuring the water 
for a tree, first measure out what they thought to be the proper 
amount, then hesitate as to whether it was enough, and finally dip 
out a second or even a third portion. Those second and third dips 
meant less available gas, and the common multifold guessing in the 
measure of water under the old system has been directly responsible 
for irregular results. 
