94 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
As sodium has a lower atomic weight than potassium, a greater 
yield of gas is obtained from the same weight of the eyanid of the 
former and a larger amount of sulphuric acid is required for its 
decomposition. According to this reaction, 1 ounce (avoirdupois) 
of sodium eyanid requires 1 ounce (avoirdupois) of sulphuric acid, 
H 2 S.0 4 , or 1.07 ounces of commercial sulphuric acid containing 93 
per cent of sulphuric acid, winch is equivalent to 0.56 fluid ounce. 
As before noted, to get the best yield of gas the sulphuric acid must 
be in considerable excess, when the reaction would be : 
NaCN + H 2 S0 4 = NaHS0 4 + HCN, 
or for each ounce of sodium eyanid there would be required 2.14 
ounces (avoirdupois) of 93 per cent sulphuric acid, equivalent to 1.12 
fluid ounces. To determine the best proportions of sodium eyanid, 
sulphuric acid, and water to use in actual practice in order to obtain 
the largest yield of gas, the following experiments were carried out, 
using pure sodium eyanid containing 94 per cent actual sodium 
eyanid, the remainder being mainly moisture, and commercial sul- 
phuric acid "66° Baume," which on analysis showed 93.52 per cent 
sulphuric acid. Three-ounce (avoirdupois) portions of the sodium 
eyanid were employed in each experiment and varying amounts of 
sulphuric acid and water were taken. The decomposition was car- 
ried out in tall beakers of 4-liter capacity in order to prevent any 
possibility of loss from spattering. The water was first measured 
into the beaker, then the acid added, and the weighed package of eyanid 
was immediately dropped in. After standing 40 minutes the residue 
was washed out of the beaker into a graduated flask, cooled, made up 
to mark, thoroughly mixed, and aliquots taken for the determination 
of the amount of hydrocyanic acid remaining in solution. As has 
been shown by experiments herein reported, the difference between 
the total amount of eyanid in the quantity of material taken and 
that remaining in the residue does not represent correctly the amount 
of gas given off and available for fumigating purposes, but when 
operating on a pure eyanid, the less hydrocyanic acid remaining in 
the solution the greater will be the yield, and for measuring the rela- 
tive efficiency of the different mixtures of acid and water it is only 
necessary to determine the amount of hydrocyanic acid in the residue. 
In all determinations of eyanid Liebig's 1 method has been used. 
In every case where ammonia was present in the solution, due to 
previous decomposition of the eyanid (in which case the end reaction 
would not appear as soon as it should, due to the solvent action of 
ammonia on the silver eyanid), a few drops of a dilute solution of 
potassium iodid were added in order to overcome this source of error, 
silver iodid being insoluble in dilute ammonia. 
' Volumetric Analysis, Sutton, 9th ed. rev., p. 200. 
