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Unformatted text preview: the pressures available in the laboratory is a hazardous material. If air under pressure is directed toward intact skin, it can penetrate without making any visible opening and cause
the nearby skin area to expand like a balloon. The pain from such an event can be
severe, and the damage to the tissues can require hospitalization. Never direct air
under pressure toward yourself or any other person.
Two categories of hazards are involved in the use of UV lamps: those inherent in the
radiation itself and those associated with the operation of the lamps.
All radiation of wavelengths shorter than 250 nm should be considered dangerous.
Operate UV irradiation systems only in a completely closed radiation box. Wear protective safety goggles with UV-absorbing lenses; your eyes can be accidentally exposed
to light in this wavelength region. Wear slacks and a long-sleeved shirt to protect
your skin. Skin areas exposed to illumination from UV lamps can be painfully burned,
similar to severe sunburn.
Mercury arc lamps should be adequately cooled and operated within an enclosure
designed to prevent damage by explosion of glass fragments and leakage of mercury
vapor; make sure that the lamp you use is so equipped.
Do not handle mercury arc lamps with your bare hands. Deposits of oil from your
skin damage the outer glass surface. If these oily residues are not thoroughly removed,
they will burn into the glass, causing localized buildup of heat during the operation of
the lamp. The lamp may then overheat, and the outer envelope may crack.
At the end of the useful life of a mercury arc lamp, buildup of UV-absorbing films
on the interior glass walls may cause the temperature to rise above the safe operating
point. Therefore, make sure that the running-time meter on the lamp works, so you
can know the total time the lamp has been operated. Controlling Temperature
Many reactions must be initiated by heating. Because the rates of most chemical reactions increase as the temperature increases, highly exothermic reactions can become
dangerously violent unless provisions are made for adequate cooling. Some exothermic reactions have an induction period. In such reactions, if too much reagent was
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- Spring '07