Location: Outside U.S.
Date: Fall 2011
Can you tell me how silica gel is correctly categorized (I see it called narrow or large pore as well as Type A, B and C)? What is the difference? Are they all used the same way, as a desiccant?
The "A", "B" and "C" designations of silica gel refer to the pore size.
The "A" type has large numbers of very small pores, and is generally
used as a desiccant. Water vapor is adsorbed into these pores, or
water vapor already adsorbed, is released upon heating. This is the
type normally found in small bags packed in electronic and optical
The "C" type has somewhat fewer (but still very large numbers) large
pores. This type is used for large volumes of liquid water absorption,
commonly as cat litter.
The "B" type has pore sizes that are smaller than the "C" type, but still
larger than the "A" type. It is also used a liquid absorber.
Each of the three types is chemically identical, but pore size is
optimized for the use to which they are put.
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Update: June 2012