ALLIED
DESICCANT PRODUCTS.
Alongside
silica gels, we offer a number of related products. Namely :
activated carbon, molecular sieves , capsilgels (silica gel in capsules),
humidity indicator cards and
papers and desiccant and fluograde activated
aluminas.
ACTIVATED CARBON
A granular coconut shell carbon
suitable for various air and water treatments (including diving
equipment applications) is available from stock - packed in 2.5kg, 7.5kg and 15kg
containers.
DESICCANT MOLECULAR SIEVES.
Molecular sieves are
desiccants with differing properties to those of silica gel. With the appearance of small
opaque pinkish beads, molecular sieves are synthetically produced, highly porous
crystalline metal-alumino
silicates. They have many internal cavities that are linked by window openings of precise
diameters. It is
these diameters (measured in Ångstroms) that classify molecular sieves - 3Å, 4Å, 5Å,
and 10Å (also known
as 13X). Adsorption occurs only of molecules with smaller diameters than these cavity
openings. Larger
molecules will be excluded from adsorption. Preferentially adsorbed are molecules of
greater polarity.
This makes molecular sieves ideal for adsorption of water from air and
liquids, as water molecules are
both polar and very small.
Molecular sieves will adsorb water molecules and other contaminants from liquids and gases
down to
very low levels - often just 1 part per million.
Examples of the applications of the differing molecular sieve grades are :
Grade 3Å. Dries unsaturated gases and organic liquids (e.g methanol).
Used to remove water from cleaning fluids in ultrasonic baths.
Grade 4Å. Is a general dryer of liquids, natural gases. Also an
excellent adsorber of carbon dioxide.
Grade 10Å (13X). Is used in air prepurification (due to its high water
and carbon dioxide adsorption capacity)
and also adsorbs sulphur compounds ('sweetens'). It will remove decomposition products
following
the quenching of arcing in electrical products.
Molecular sieves properties as desiccants differ from silica gel in a
number of ways :
(1) They adsorb water vapour more rapidly than silica gel.
(2) They will reduce water vapour to much lower levels than silica gel, making their
use essential
when a very dry product or atmosphere is required.
(3) They perform more effectively as moisture adsorbers at higher temperatures
(greater than 25°C) than silica gel does.
Molecular sieves
of grades 3Å, 4Å and 10Å (13X) are stock items.
They are sub-classified by their bead sizes, typically 1.6 - 2.5 mm
and 2.5 - 5.0 mm.
They are available in the same bulk pack sizes as silica gel - 500 gram or 1 kg in
foil packs or polytubs.
3 kg and 10 kg in polytubs. 25 kg in metal drums and larger.
Molecular sieve sachets are supplied to customers requirements. They can
be made with any of the
grades mentioned, in any sachet from ½ gram to 500 gram and above.
CAPSILGELS - SILICA GEL IN CAPSULES.
Capsilgels are transparent
hard capsules containing silica gel. The capsule is made from hard gelatine.
It consists of two cylindrical parts, a body with a hemispherical base and a corresponding
cap of the same
shape, but shorter. The internal diameter of the cap and the external diameter of the body
are virtually equal.
They are held together by a pair of circumferential grooves, that interlock when the
filled body and cap
are pressed together. Both non and self-indicating silica gels can be used to fill
the capsule.
Three standard sizes are available. These are size 1, size 00 and size 000.
All figures are
approximate.
Capsilgels breathe and adsorb
moisture in the same way as silica gel sachets do. They are ideal for use in
situations where the physical space available to site a desiccant is restricted, such as
in small spaces
inside moisture sensitive scientific instruments or other electronic assemblies.
HUMIDITY INDICATOR CARDS AND PAPER.
The actual moisture content of
air within a package expressed as a percentage of its saturation moisture content,
is termed the Relative Humidity (RH). The crucial factor in preventing corrosion
and mould growth to
stored or in transit items, is to keep the RH below 50%. Carefully calculated, the use of
silica gel sachets
will keep the RH below this level. This can be confirmed by the use of humidity
indicator cards
or papers which give a guide to the RH level.
We currently offer the following humidity indicators :
(1) Safe/Unsafe cards or paper. The paper will change colour
dependent on the RH level. A pink paper
indicates that the silica gel sachets need changing to prevent moisture damage
occurring.
A blue paper indicates that the RH is at safe levels. Similarly, the indicator card has a
spot that changes
colour in the same fashion. This can be compared to a blue fixed colour on the card
- if the spot
shows the same colour or a darker blue than the fixed panel, then the RH is at safe
levels.
A pinker colour and the RH is considered unsafe.
(2) Six spot indicator cards. Each spot represents a RH level from 10 -
60%. The higher
up the card the spots change from blue to pink, the higher the RH. This allows
an accurate reading of the humidity level and again, aids in indicating when
silica gel sachets require replacing.
(2) Three spot indicator cards. Similar to six spot cards, but with each
spot
representing a RH level from 10 - 30%.
All of the humidity indicator cards and papers are sold in small or large quantities.
ACTIVATED ALUMINA.
Desiccant grade activated
alumina is a highly porous form of aluminium oxide. It has the appearance
of white chalky beads. Standard stock sizes have 1 - 2 mm, 2 - 5 mm or 5 - 8 mm
beads.
An adsorbent from liquids and gases, it is supplied to customers requirements, usually in
bulk packs.
A fluograde alumina is also sometimes available (for fluoride removal
from water).
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