Soaps and detergents remove dirt and grease from skin and clothes. But all soaps are not equally effective in their cleaning action. Soaps are the Na and K salts of higher fatty acids such as Palmitic acid, Stearic acid and Oleic acid.
The cleansing action of soaps depends on the solubility of the long alkyl chain in grease and that of the -COONa or the -COOK part in water.
Whenever soap is applied on a dirty wet cloth, the non polar alkyl group dissolves in grease while the polar -COONa part dissolves in water. In this manner, an emulsion is formed between grease and water which appears as foam.
The washing ability of soap depends on foaming capacity, as well as the water used in cleaning. The salts of Ca and Mg disrupt the formation of micelle formation. The presence of such salts makes the water hard and the water is called hard water. These salts thus make the soap inefficient in its cleaning action.
Sodium Carbonate when added to hard water reacts with Ca and Mg and precipitates them out. Therefore sodium carbonate is used in the treatment of hard water.
This project aims at finding the foaming capacity of various soaps and the action of Ca and Mg salts on their foaming capacity.
Soap is an anionic surfactant used in conjunction with water for washing and cleaning, which historically comes either in solid bars or in the form of a viscous liquid. Soap consists of sodium or potassium salts of fatty acids and is obtained by reacting common oils or fats with a strong alkaline in a process known as saponification. The fats are hydrolyzed by the base, yielding alkali salts of fatty acids (crude soap) and glycerol.
The general formula of soap is
Fatty end water soluble end
CH3-(CH2) n – COONa
Soaps are useful for cleaning because soap molecules have both a hydrophilic end, which dissolves in water, as well as a hydrophobic end, which is able to dissolve non polar grease molecules. Applied to a soiled surface, soapy water effectively holds particles in colloidal suspension so it can be rinsed off with clean water. The hydrophobic portion (made up of a long hydrocarbon chain) dissolves dirt and oils, while the ionic end dissolves in water. The resultant forms a round structure called micelle. Therefore, it allows water to remove normally-insoluble matter by emulsification.
The foaming capacity of soap depends upon the nature of the soap and its concentration. This may be compared by shaking equal volumes of solutions of different samples having the same concentration with same force for the same amount of time. The solutions are then allowed to stand when the foam produced during shaking disappears gradually. The time taken for the foam to disappear in each sample is determined. The longer the time taken for the disappearance of the foam for the given sample of soap, greater is its foaming capacity or cleansing action.
Five 100ml conical flasks, five test tubes, 100ml measuring cylinder, test tube stand, weighing machine, stop watch.
Chemical Requirements: Five different soap samples, distilled water, tap water.
1. Take five 100ml conical flasks and number them 1,2,3,4,5. Put 16ml of water in each flask and add 8 Gms of soap.
2. Warm the contents to get a solution.
3. Take five test tubes; add 1ml of soap solution to 3ml of water.
Repeat the process for each soap solution in different test tubes.
4. Close the mouth of the test tube and shake vigorously for a minute. Do the same for all test tubes and with equal force.
5. Start the timer immediately and notice the rate of disappearance of 2mm of froth.
The following outcomes were noticed at the end of the experiment
|Test Tube no||Vol. of soap solution||Vol. of water added||Time taken for disappearance of 2mm|
The cleansing capacity of the soaps taken is in the order:
Santoor > Dove > Cinthol > Tetmosol > Lux
From this experiment, we can infer that Santoor has the highest foaming capacity, in other words, highest cleaning capacity.
Lux, on the other hand is found to have taken the least amount of time for the disappearance of foam produced and thus is said to be having the least foaming capacity and cleansing capacity.
Test for hardness in water
Test for Ca2+ and Mg2+ salts in the water supplied
Test for Ca2+ in water
H2O +NH4Cl + NH4OH + (NH4)2CO3
Test for Mg2+ in water
H2O +NH4Cl + NH4OH + (NH4)3PO4
The tests show negative results for the presence of the salts causing hardness in water. The water used does not contain salts of Ca2+ and Mg2+. The tap water provided is soft and thus, the experimental results and values hold good for distilled water and tap water.
Parts of this project have been referred from foreign sources and have been included in this investigatory project after editing.
The references of the sources are as follows:
Together With Lab Manual Chemistry-XII
Comprehensive Chemistry – 12
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