Quality of Auxiliary Chemicals used.

a. 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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