50 HYDROCYANIC-ACID GAS FUMIGATION IX CALIFORNIA. 
immediately attacks the hydrocyanic-acid gas and decomposes it to a 
great extent. Hence, as the presence of sodium chlorid. in a cyanid 
produces a partial decomposition of the hydrocyanic-acid gas when 
liberated, the ultimate result is that less gas is given off than from 
a cyanid of the same degree of strength which is free of it. 1 Exten- 
sive experiments carried out by the Bureau of Chemistry of this 
department showed that the presence of sodium chlorid in a reaction 
causes a very marked decomposition of the hydrocyanic acid. 
Experiments with two different cyanids each of which has had a 
limited usage in California showed that the amount of sodium 
chlorid in one caused a decomposition of 9.76 per cent of the total 
hydrocyanic acid, the other of 34.07 per cent. An experiment per- 
formed with a cyanid having a very large quantity of sodium chlorid 
in the reaction resulted in a decomposition of over 92 per cent of the 
total amount of gas, only a little over 7 per cent being evolved. 
The results of these experiments bring to our attention a second 
requirement in the purchasing of a cyanid. That it be of a certain 
degree of purity is no longer the only consideration. It is of equal 
importance that the cyanid be practically free of sodium chlorid. 
Possibly . extensive and expensive refining would be necessary to 
eliminate all traces of sodium chlorid from a cyanid. Such a condi- 
tion would be preferable but can not be demanded at the risk of 
increased cost. We can, however, reasonably expect a high degree 
of purity, and the writer would condemn as unsuitable for use in 
fumigation any cyanid containing in excess of 1 per cent of sodium 
chlorid. This does not mean that every cyanid used should be 
examined to determine if it contains in excess of this quantity of 
sodium chlorid. A potassium cyanid 98-99 per cent pure has such 
a small margin for impurities that it will not contain any objection- 
able quantity. A potassium cyanid guaranteed as 98-99 per cent 
pure can be used with entire safety provided its purity measures up 
with the guarantee. 
NATURE OF THE RESIDUE. 
The residue resulting from the generation of hydrocyanic-acid gas 
is usually a bluish or greenish colored liquid consisting for the most 
part of water. It also contains sulphate of potassium, more or less 
sulphuric acid, and some hydrocyanic acid held in solution. This 
combination of substances is of a very poisonous nature. Neverthe- 
less, some writers on fumigation, considering the plant-food elements 
which this residue contains, have advised that the residue was of 
much importance as a fertilizer and should be spread over the ground 
for such a purpose. This is an instance of the too frequent tendency 
1 The decomposing action of sodium chlorid on cyanid used in fumigation was first mentioned by 
Newell in Bulletin 15, Georgia State Board of Entomology, 1905. 
