oisture from the breath and saliva would condense at the end of
the gun, drip onto the specimen and cause stains which might prove
indelible. The second tube contains a small amount of iodine crystals
which are vaporized by the heat of the breath, augmented by the warmth
of the hand cupped around the tube containing the iodine. This vapor
is blown onto the specimen (fig. 420). Glass wool serves to hold the
calcium chloride and iodine in place.

[Illustration: 420. Iodine fuming gun in use.]

Due to the amount of physical exertion involved, the gun is generally
limited to the examination of a few small specimens. Where a large
number of specimens are to be treated, the fuming cabinet, a
box-shaped wooden receptacle with a glass front and top permitting the
operator to control the amount of fumes in the cabinet and observe the
development of the latent impressions, is used (fig. 421). The fumes
are generated by placing a small alcohol burner under an evaporating
dish containing the iodine crystals. This is set in a hole cut in the
bottom of the cabinet. As soon as the fumes begin to appear in
sufficient amounts, the burner is removed. The specimens may be hung
in the cabinet by wooden clothes pins fastened to a removable stick
which is supported by wooden strips affixed near the top edges of the
cabinet. The top of the cabinet is removable to permit access.
Diagrams for the construction of the iodine gun or fuming cabinet will
be furnished on request to members of the law enforcement profession.

Many specimens bear small, greasy areas which, in addition to any
latent impressions of a greasy nature, will also appear
yellowish-brown after exposure to iodine fumes. All these stains will
eventually disappear if the specimen is placed in a current of air
from a fan or vent. All latent impressions on an object will not be
developed by the iodine process but only those containing fat or oil.
Due to this fact and the fact that iodine evaporates from the surface,
it is used prior to (it cannot be used afterward), and in conjunction
with, the silver nitrate process.

[Illustration: 421. Iodine fuming cabinet in use.]

No ill effects have been noted from contact with small amounts of
iodine vapor but prolonged or excessive contact will produce
irritation of the skin and respiratory passages. To prevent gradual
loss of the chemical through evaporation and the corrosion of
surrounding metal surfaces, iodine crystals should be ke