Indicating silica gel is a highly useful variety of desiccant which is used by many industry for absorption purpose.

1. Indicating Silica Gel

2. What is Absorption ???
&
What is Adsorption ???

3. Description of Picture goes here.
Absorption is the passage of one substance into or
through the bulk of another medium….
Absorb substance spread to saturate to hole of
medium to form a solution & get mixed with other
medium is so well that one fail to recognise its
existence.

4. Adsorption is the adhesion or sticking together
of molecular of gas, liquid or dissolved soilds to
the surface of soild or sometimes a liquid…..the
molecules are loosely held by the surface & can
be easily removed

6. Adsorbate : - It is the substance which is
adsorbed at the surface of another substance
Examples are: gases, dyes, water vapors etc.
Adsorbent :- It is the substance which adsorbs
the other substance at its surface. Examples are:
Silica gel, Activated Alumina, Molecular
Sieves,Activated Carbon & Clay etc

7. Adsorption process

8. Chemisorption: Chemisorption is a kind of
adsorption which involves a chemical reaction
between the surface and the adsorbate. New
chemical bonds are generated at the adsorbant
surface
Physisorption:It also called physical adsorption
Physical adsorption: Van der Waals attraction
between adsorbate and adsorbent. The attraction
is not fixed to a specific site and the adsorbate is
relatively free to move on the surface. This is
relatively weak, reversible, adsorption capable of
multilayer adsorption

9. Adsorption Equilibria / Capillary Condensation:
If the adsorbent and adsorbate are contacted long
enough an equilibrium will be established between
the amount of adsorbate adsorbed and the amount
of adsorbate in solution. The equilibrium
relationship is described by isotherms

10. Types of Adsorbents:-
 Silica gel
Molecular Sieves
Activated Alumina
Activated Carbon
Clay

11. SILICA GEL
(IS 3401:1992)
Silica gel is adsorbents in a granular, porous form of Silicon
Dioxide made synthetically from Sodium Silicate
Silica gel is an amorphous form of silicon dioxide, which is
synthetically produced in the form of hard irregular granules
(having the appearance of crystals) or hard irregular beads.
A microporous structure of interlocking cavities gives a
very high surface area (800 square meters per gram).
It has an average pore size of 2.4 nanometers and has a
strong affinity for water molecules

12. Manufacturing Process.
Silica is prepared by mixing a sodium silicate
solution with sulphuric or hydrochloric acid. The
solution is then filled up in the pits for
crystallisation. The crystals are then washed with
water to remove impurities & then dried. The
dried Silica is then sieved as per the required
sized.
Na2 SiO3+2HC1+nH2O → 2NaC1+SiO2•nH2O+H2O

13. Types of Silica gel
Non- Indicating Silica Gel
(Does not change colour after adsorbing
moisture)
Indicating Silica Gel
( Changes it colour after adsorbing moisture )

14. Indicating Silica gel
Silica Gel Blue
&
Silica Gel Orange

15. Silica Gel Blue
Blue Silica gel is prepared by impregnating White
Silica gel with Cobalt Chloride - an indicator, which
provides the Blue colour appearance. When free
from moisture it will be blue in colour and after
adsorbing moisture the particles turn into pink
It is the cobalt in the cobalt chloride indicator that is
responsible for the toxic labelling and disposal
restrictions on this product.
It is still though considered as non-hazardous for
transportation purposes.

16. Technical Parameter
Description
SILICA GEL BLUE
(INDICATING TYPE)
Assay (as SiO2) Min 97%
pH 4 - 8
Bulk Density (g/ml) 0.65 - 0.85
Loss on Drying % <6
Adsorption Capacity @
100% humidity
35-40
Friability 99.5
Chloride (as NaCl) Max 0.4%
Cobalt (as CoCl2) 0.5%
Sulfates (as Na2SO4) Max 0.5%
Binder (as CaSO4) NIL
Particle Beads size (mm)
1-2 mm, 1-3 mm, 2-4 mm, 2-5
mm, 3-5 mm, 3-6 mm, 4-8 mm
Particle Crystals size
(mesh)
1-3 mesh, 3-4 mesh, 5-8 mesh

17. Silica Gel Orange
It is produced by impregnating white Silica Gel
with Phenolphthalein due to which the colour of
Silica Gel turns orange. Orange indicating
Silica Gel is gradually replacing blue Silica Gel
as the blue mixture is presumed to cause
cancer. This orange Silica in turn changes to a
translucent green after it absorbs moisture.

18. Technical Parameter
Description
SILICA GEL Orange
(INDICATING TYPE)
Assay (as SiO2) Min 97%
pH 6-8
Bulk Density (g/ml) 0.65 - 0.75
Loss on Drying % 2.0
Adsorption Capacity -
20% RH, 25 degrees C
35% RH, 25 degrees C
50% RH, 25 degrees C
9.0% w/w
12.0% w/w
22.0% w/w
Friability 99.5
Chloride (as NaCl) Max 0.4%
Phenolphthalein 0.2%
Colour RH 20%
RH 35%
RH 50%
Yellow/ Dark Orange
Light Orange
Cyan / Blue dark
Available Particle size 2-5 mm, 3-5 mm, 6-8 mesh

19. SILICA GEL BLUE & SILICA GEL ORANGE
PROPERTIES Silica Gel
Blue
Silica Gel
Orange
Remarks
pH 4-8 6-8 Controlled pH conditions
Loss on Drying% Max 6% Max 2% Better dried product
Adsorption Capacity at
100% humidity
Min 35% Min 38% Better capacity for
moisture pick up
Colour Indication Blue-White-
Pink
Orange-
Brown-
Cyan(Green)
Better & clear indication
observations
Cobalt 0.4-0.6% NIL Cobalt is carcigen & it is
harmful
Environment Safety Hazarder Non-hazarders E C Directive 67/548/EEC

20. SOME OF ITS APPLICATION
Transformer Breather

21. Drying Flowers.

22. Sound Recording Studio.

23. Camera Lens

24. Pet Containers for storage purpose

25. Moisture Trapper.

26. Cat litter Silica Gel

27. Pouches for various uses.

28. Hearing Aids.

29. Thanks You.