Silica gel is the most commonly encountered desiccant in everyday
life as the beads are packed in a vapor-permeable plastic. In this
form, it is used as a desiccant to control the high temperatures of
the local humidity in order to avoid degradation of some goods.
Because of poisonous dopants (toxic agents) and their nature of very
high absorption of moisture, silica gel packets usually bear
alarming warnings for the user not to eat the product contents. If
consumed, then the pure silica gel is unlikely to cause acute or
chronic illness. On general basis, Food-grade desiccant should not
posses any poison or toxic substance which would cause long-term harm
to humans if consumed in the quantities normally included with the
items of food.

The general theory of Column chromatography, in chemistry is
explained as a method used to purify individual chemical compounds
from mixtures of different compounds. It is often used on scales of
micrograms up to kilograms for preparative applications . The main
advantage of silica
gel column chromatography is the relatively
low cost and disposable feature used at stationary phase of the
process. This prevents the cross-contamination and the degradation at
the stationary phase, due to recycling.

Silica gel is known to have a high surface area, around 800 m²/g,
that allows it to absorb water instantaneously, making it serve its
purpose as a desiccant, a drying agent. But once saturated with
water, the gel can again be regenerated by heating it to the
temperatures of 120 °C ranging to 250 °F for almost two hours.
Some types of silica gel will \"pop\" over when exposed to
enough water. preparation of different compositions of silica gel
will explain us various forms of orange silica gel, blue
silica gel and their evolution. Initially, a solution of sodium
silicate is acidified to produce a gelatinous gel precipitate that is
washed, and then dehydrated to produce colorless silica gel. When a
visible indication of moisture content of the silica gel is required,
ammonium tetrachlorocobaltate(II) i.e (NH4)2CoCl4 or cobalt chloride
CoCl2 is added, which will cause the gel to be blue when dry and
this produces the silica gel blue and pink when hydrated. An
alternative indicator is also taken into methods, methyl violet which
is orange when dry and this produces us with the silica gel orange
and green when hydrated.

Uses of silica
gel bags and silica gel packets over
silica gel column chromatography phenomenon lay out widely.
Silica gel may also be used to keep the relative humidity (RH) as low
as possible , inside a high frequency radio or satellite transmission
system waveguide. Excessive buildup of moisture within a waveguide
can cause arcing inside the waveguide itself, damaging the power
amplifier that\'s actually feeding it. Not only this, also the beads
of water that form and condense inside the waveguide change the
characteristic features of impedance and frequency, diminishing the
the signal. It is common theory for a small compressed air system, to
be employed to circulate the air inside the waveguide over a jar
volumes of silica gel, similar to that of a small home aquarium pump.

Silica gel is also used to dry the humid in the industrial
compressed air systems. Air from the compressor discharge flows all
through a bed of silica gel beads. The silica gel absorbs this
moisture from the air, preventing damage at the point of use by the
compressed air due to either condensation or moisture. The same
system and process is used to dry out the humid and dry the
compressed air on railway locomotives, where condensation in the
brake air pipes can lead to brake failure. Silica gel is also
sometimes used as a preservation tool to control relative humidity in
closed structures of museum and library exhibitions and storage
spaces. Other applications include diagnostic test strips, syringes,
inhalation devices, hospital sanitation kits and drug test kits.