Quality of
surfactants like wetting, scouring agents:
- Solid Content:
 Weigh
accurately 10 grams of the material to be tested in a pre-weighed
porcelain crucible; let the weight be "A" grams. Dry the crucible in a
high temperature electrical over at 95C for 2 hours. Take out the
crucible and re-weigh it; let the weight after drying be "B" grams.
Then the solid content of the material = 100 x (B-Empty Crucible wt) / (A-Empty Crucible weight).
2.
Wetting Time: Various methods
have been used for testing wetting agents. A simple test is to determine the number of seconds required for a 1-inch
square piece of No. 6 canvas to sink in a 1 per cent solution of the
wetting agent at 22 to 23 C. Another method is that described by
Draves ( I ) , in which a 5-gram skein of cotton yarn is used.
Although these simple sinking tests give an ../default of the properties of a
wetting agent, they are not conclusive and do not give a full picture of
their value in treating baths. This is true since so-called wetting agents
usually have other properties besides their wetting properties, and in
some cases these other properties may be of much greater importance than
their wetting properties.
3. Ionic
Nature: Ionic nature of a wetting
agent may be decided by a very simple test. Dissolve 2 grams of the
wetting agent in 100 ml of distilled water. Call this as Solution 'A'.
-
Anionic: Take about 10 ml of this solution (A)
in a 20 ml test tube. Add 10 drops of 2N Hydrochloric acid in to this
and shake well. If a white cloud or precipitate is formed, then the
surfactant tested is Anionic in nature.
-
Cationic: Take about 10 ml of the solution (A) in a 20 ml test
tube. Add 10 drops of 2N sodium hydroxide solution and shake well. If
a White cloud or precipitate is formed, then the tested product is
Cationic in nature.
-
Non-ionic: If no precipitate or cloud is formed either with acid
or alkali, then the material tested is Non-ionic in nature.
-
Amphoteric: Amphoteric wettings will make a very slight
white precipitate with acids and the precipitate will not settle down
to the bottom or the test tube even after few hours. It will remain in
suspension.
4. Cloud Point: The non-ionic surfactants exhibit
a property called cloud point. Upon slowly raising the temperature of 2
grams per liter of solution (prepared using distilled water), at a
particular temperature the clear solution becomes cloudy.  That
temperature is called the cloud point of that non-ionic wetting agent.
After the cloud point temperature it is said that the nonionic products do
not exhibit its intrinsic properties, such wetting, scouring, rewetting,
emulsifying etc. So if a wetting agent's cloud point is 70C, then it
should be understood that above 70C, it should not used as wetting agent.
For example if you are doing scouring and bleaching at 90C, then a 70C
cloud point wetting agent is not suitable for this purpose. Most of the
non-ionic wetting agents have the cloud of more of less 70°C.
 5. Foaming Test: Formation of foam during
processing especially in jet and soft-flow type of machineries is a big
headache for the dyer. So in these machines people prefer only no-foaming
or very low foaming wetting agents only. Compare two wetting agents by
making .01% solution, in two 500 ml measuring jars. Shake the jars
for about 3 minutes and keep them intact for some time. Compare the height
of the foam. Lower the height better the wetting agent.
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