What is silica gel and why do I find little
packets of it in everything I buy?
Little packets of silica gel are found in all
sorts of products because silica gel is a desiccant
-- it adsorbs and holds water vapor. In leather
products and foods like pepperoni, the lack of
moisture can limit the growth of mold and reduce
spoilage. In electronics it prevents condensation,
which might damage the electronics. If a bottle
of vitamins contained any moisture vapor and were
cooled rapidly, the condensing moisture would
ruin the pills. You will find little silica gel
packets in anything that would be affected by
excess moisture or condensation.
Silica gel is nearly harmless, which is why you
find it in food products. Silica, or silicon dioxide
(SiO2), is the same material found in quartz.
The gel form contains millions of tiny pores that
can adsorb and hold moisture. Silica gel is essentially
porous sand.
Silica gel can adsorb about 40 percent of its
weight in moisture and can take the relative humidity
in a closed container down to about 40 percent.
Once saturated, you can drive the moisture off
and reuse silica gel by heating it above 300 degrees
F (150° C).
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