THE HYDROCYANIC ACID GAS TREATMENT 
FOR THE FLOUR MOTH 
F. L. W'ASnUURN, STATE ENTOYIOLfM ilST. 
So many recjuests have recently reached the Entomologist's office 
for information upon the method of treating mills with cyanide that a 
rejjrint of a previous circular, the issue of which is entirel\- exhausted, 
seems necessary at this time. 
There is no question but that the heat method as outlined by Dean 
of Kansas is the safest and best measure to adopt where it is feasible. 
This consists in kee])ing all parts of the treated mill at a temperature of 
from 123° to 125° ¥. for several hours. It is not always ])ossible to 
do this unless a mill is especially fitted wdth a heating outfit for this 
purpose. For this reason, and because the various other new fumi- 
gants have not been sufficiently tested, even if their cost does not make 
them ])rohibitive, the cyanide method herein described appears to be 
in the majority of cases the most efficient, though where the above 
temperature can he secured and maintained there is no (juestion hut 
that the heat method is most ipracticak 
This publication will be mailed without charge to any miller re- 
questing same as long as the issue lasts. Experiment Station Bulletins 
go through the mails with the Federal frank, hut State Entomologist 
Circulars are not so privileged. Applicants, therefore, should accom- 
pany their recpiests with a two-cent stamp. 
It is to be noted that it is practically impossible at this time to 
purchase cyanide of potash, l^ffirtunately we have an excellent sub- 
stitute in the shape of cyanide of sodium which gives (juite as effective 
results and is less expensive than the potash compound in that one 
requires only four-fifths as much cyanide of sodium as cyanide of 
])otash for fumigation. For example, it is necessary to use only four- 
fifths of three pounds, or 2.4 pounds, to a charge when employing 
cyanide of sodium. We would suggest, wdiere sodium is used, com- 
puting the amount of material needed (cyanide, acid, w^ater and jars 
for each story) on the same basis as wdth cyanide of potash and then 
actualiy using only four-fifths of this amount of cyanide of sodium, hut 
