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To destroy insects by means of heat, the room or heating box should 
be kept at a temperature of 130 degrees F. for at least 6, and preferably 
12, hours. A temperature of more than 140 degrees F. is likely to damage 
specimens, and indeed many of them cannot safely be heated to even 130 
degrees F. If this method is to be used in a museum, the construction of 
a special room or large box with heating coils and automatic thermostatic 
control is advisable. 
Advantages. Effective if properly applied; no expense in the use of 
low temperature; large rooms and even buildings can be treated. 
Disadvantages. In the case of cold, not always available; in the case 
of heat, only some specimens can be treated and specially constructed 
apparatus is required. 
DRY ICE 
Dry ice is a trade name for solidified carbon dioxide gas. It is a homo- 
geneous, white, marble-like substance with a temperature of about 110 
degrees below zero Fahrenheit. If may prove very useful in an emergency, 
when fumigation is for some reason inadvisable or impossible. The dry 
ice is placed in the storage room, all cracks around doors and windows 
having been sealed. The quantity can only be determined by experiment, 
depending as it does on outside temperature, the size of the room, and the 
thermal conductivity of the walls, floor, and ceiling. The dry ice vaporizes 
slowly giving off carbon dioxide, a harmless gas not to be confused with 
the deadly carbon monoxide, heavier than air, and the temperature of the 
room is rapidly reduced. It should be brought down to zero and held 
there for at least 24 hours. Dry ice must never be handled with bare hands, 
as frost-bite would be the immediate result. 
Advantages. Useful in emergencies, when fumigation is impossible; 
effective if the temperature is brought down to zero and held there. 
Disadvantages. May prove somewhat expensive, and is not always 
readily obtained except in large cities. 
NAPHTHALENE 
This material, though extremely useful, even essential, is not to be 
considered as a fumigant but merely as a repellant. Though it is true 
that it is lethal to insects when high concentrations are used, the fumes 
are given off very slowly and it is desirable that a fumigant should act 
rapidly so that damage may be arrested at once. Naphthalene may be 
obtained both in flakes and in balls. The balls present but little surface 
to the atmosphere and are not so effective as the flakes which vaporize 
much more rapidly, presenting as they do a much larger surface. It 
should always be used liberally in storage cases, and sprinkled in the trays. 
If, on opening a storage case, the air is sufficiently permeated with naphtha- 
lene vapour to make the eyes and nose smart, or if crystals of naphthalene 
have formed on the inside of the case, it may be taken for granted that it is 
being used in sufficient quantities and that there will be no danger from pe3ts. 
Paradichlorobenzene is very similar to naphthalene in its effects, and 
is equally satisfactory. As it is, however, more expensive, there seems to 
be no good reason for preferring it to naphthalene. 
