28. Procedure
28.1 Weigh 10 g of the sample into a 250-mL Erlenmeyer flask. Add 10 mL of NaOH (100 g/L) and heat the mixture under a reflux condenser for 2 h.
28.2 Cool the flask and substantially neutralize the NaOH with H2SO4 (1 + 4); then add an excess of approximately 25 mL of H2SO4 (1 + 4) followed by 20 mL of n-hexane.
28.3 Complete the determination in accordance with 27.2-27.8.
29. Calculation
29.1 Calculate the percentage of glycerin as follows:
where:
G = percentage of glycerin.
M = millilitres of 0.05 N NaOH solution used to titrate the sample,
M1 = millilitres of 0.05 N NaOH solution used to titrate the blank,
N = normality of the NaOH solution,
S = grams of sample used, and
0.92 = an empirical factor derived from experimental data (not to be confused with 0.0921, which is the stoichiometric glycerin value).
30. Precision and Bias
30.1 Precision - There are no interlaboratory test data available to establish a statistical statement of precision.
30.2 Bias - There are no interlaboratory test data available to establish a statistical statement on bias.
31. Keywords
31.1 analysis; extraction; fat content; fluid content; free alkali content; free fatty acid content; glycerin content; insolubles content; lubricating grease; petroleum oil content; soap content; Soxhlet apparatus; thickener content; water content