50 HYDROCYANIC-ACID GAS FUMIGATION IN 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. 



XATURE 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. Tins 

 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. 



