Claims:1. A method for the estimation of free alkali in soap samples, the method comprising steps of:
(a) obtaining and weighing a soap sample;
(b) dispersing the soap sample in water to obtain a first dispersion;
(c) contacting an alkaline earth metal salt with the first dispersion to obtain a second dispersion;
(d) filtering the second dispersion to obtain a filtrate; and,
(e) analyzing the filtrate to quantitatively estimate the amount of free alkali in the soap sample.
2. The method as claimed in claim 1, wherein the water is neutralized water.
3. The method as claimed in claim 1, wherein the alkaline earth metal salt is selected from the group consisting of calcium chloride, magnesium nitrate, magnesium chloride, calcium nitrate, and combinations thereof.
4. The method as claimed in claim 3, wherein the alkaline earth metal salt is calcium nitrate.
5. The method as claimed in claim 1, wherein the soap sample to the alkaline earth metal salt weight ratio is in the range of 1:0.5-1:2.
6. The method as claimed in claim 5, wherein the soap sample to the alkaline earth metal salt weight ratio is 1:1.
7. The method as claimed in claim 1, wherein the analysis is carried out by a method selected from the group consisting of acid-base titration and potentiometric titration.
8. The method as claimed in claim 7, wherein the acid-base titration comprises steps of:
(a) contacting the filtrate with an indicator to obtain a stable color solution;
(b) subjecting the stable color solution to titration by an acid titrant;
(c) determining the end point of titration based on a change in color; and
(d) estimating the amount of free alkali in the sample based on the volume of aqueous acid consumed during titration.
9. The method as claimed in claim 8, wherein the indicator is an acid-base indicator selected from the group consisting of phenolphthalein and bromothymol blue.
10. The method as claimed in claim 9, wherein the indicator is phenolphthalein.
11. The method as claimed in claim 8, wherein the acid titrant is an aqueous mineral acid selected from the group consisting of aqueous hydrochloric acid, and aqueous sulfuric acid.
12. The method as claimed in claim 11, wherein the acid titrant is aqueous hydrochloric acid.
13. The method as claimed in claim 12, wherein the acid titrant has a concentration in the range of 0.01 – 0.1 N.
14. The method as claimed in claim 13, wherein the acid titrant has a concentration selected from the group consisting of 0.01N and 0.1 N.
15. The method as claimed in claim 7, wherein the potentiometric titration comprises steps of:
(a) adding the filtrate to a beaker and immersing electrodes in the filtrate;
(b) adding the acid titrant to the filtrate in an incremental manner;
(c) measuring the potential;
(d) plotting graphs as a function of volume of titrant consumed; and
(e) estimating the free alkali in soap based on the graphs.
16. The method as claimed in claim 15, wherein the acid titrant is an aqueous mineral acid selected from the group consisting of aqueous hydrochloric acid and aqueous sulfuric acid.
, Description:As Attached