12 
3. The make of saeks appears to eaiise no differenee in time re- 
quired for aeid to penetrate to cyanide, as long as they are of manila, 
and are not of the heavy materia f such as is used for sugar saeks. The 
latter should be az’oided. Cloth sacks should never be used. 
4. Mills should never be fumigated for less time than over night. 
5. Tzventy-hve seconds elapsing betzveen the dropping of the 
cyanide and the first giving off of gas i)i fatal amount is a conservative 
time estimate, resultiiig from practical tests zvith the liquid at a tempera- 
ture of iqo° to i8o° F. This zeill be approximately the temperature 
of the liquid up to one-half hour after mixing the acid and zvater, zvith 
the mill at ordinary temperature. 
6. Experiments in the laboratory and practical zeork in many 
mills indicate that eggs of the flour moth are killed by this gas, and that 
other stages of the insect are reached and killed even zvhen covered b\ 
an i)ieli or more of zeebbi)ig. 
PRFXAUTIONS. 
1. Calculations as to the cubical contents of each floor to l)e fumi- 
gated must be absolutely accurate. 
2. ( let only the best material ; a poor grade of cyanide and acid 
cannot be relied upon. 
3. Ihit on the work only a few picked men, selecting them from 
amongst the most intelligent of your employes. 
4. Take every measure possible to prevent the cyanide from com- 
ing in contact with the acid until the critical moment when such con- 
tact is desired. Be sure that each step of the process has been carefully 
studied before hand. Do not hang bags as shown in Fig. 3. 
5. Provide for thorough ventilation from the outside. Do not 
enter the mill until it has been well aired for at least two hours. 
6. Removal of the jars from the building after the operation, and 
the disi)osing of the residue in a safe place calls for care, and should not 
be intrusted to men who are careless or ignorant as to the nature of the 
gas. They should be cautioned to avoid a jar which bubbles, and 
should at all times keep their faces away from the jars they are hand- 
ling. This residue, if the chemical action has been complete, is not 
poisonous, but it is acid and it is always best to “keep on the safe side.” 
It should, therefore, be placed where it will do no harm. 
7. The lumps of cyanide, when placed in the 1>ags, should be ap- 
proximately between two and four inches in diameter. 
