ASTM D500 Test Methods of Chemical Analysis of Sulfonated and Sulfated Oils
UNSAPONIFIABLE NONVOLATILE MATTER (FOR SULFATED OILS)
37. Scope
37.1 This test method covers the determination of the unsaponifiable, nonvolatile (above 80°C) matter existing in a sample of sulfated oil by saponifying the desulfated fatty matter and extracting the unsaponifiable matter from the soap solution with ethyl ether.
38. Apparatus
38.1 Saponification Flask - The apparatus required for the saponification consists of a glass flask provided with an air condenser and identical with the apparatus described in Test Method A for organically combined sulfuric anhydride (16.1.1 and 16.1.2).
39. Reagents
39.1 Ethyl Ether.
39.2 Potassium Hydroxide, Alcoholic Solution (28 g/L) - Dissolve approximately, but not less than, 28 g of KOH in ethyl alcohol and dilute to 1 L.
39.3 Potassium Hydroxide Aqueous Solution (28 g/L) - Dissolve 28 g of potassium hydroxide (KOH) in water and dilute to 1 L.
40. Procedure
40.1 The procedure consists in decomposing the sample with mineral acid, extracting the desulfated fatty matter, saponifying the latter, and extracting the unsaponifiable matter from the soap solution with ethyl ether.
40.1.1 Desulfated Fatty Matter - Determine the desulfated fatty matter as described in the determination of total desulfated fatty matter (Section 31).
40.1.2 Saponification - Accurately weigh 2 to 2.5 g of the desulfated fatty matter in the flask, add 25 mL of the alcoholic KOH solution, and simmer the contents (without loss of alcohol) for 1 h with occasional swirling, over an electric hot plate or other source of heat.
40.1.3 Extraction - Transfer the contents of the flask to a 250-mL separatory funnel and wash the flask several times with a total of 50 mL of water, pouring it into the separatory funnel. Extract the solution while still warm (about 30°C) with 50 mL of ether (rinse the saponification flask with the ether before adding it to the separatory funnel), shaking vigorously for about 1 min, and allow the layers to settle and clear. Draw off the lower layer in a second 250-mL separatory funnel and extract in a similar manner with two 50-mL portions of ether.
40.1.4 Preliminary Water Washing - Add 20 mL of water to the combined ether layer, turn the separatory funnel and contents over gently about six times, and allow the layers to settle and clear. Draw off the lower layer and discard. Wash the ether layer twice more with 20-mL portions of water, shaking vigorously after each addition.
40.1.5 Alkali and Water Washing - Add 20 mL of aqueous KOH solution to the washed ether layer, turn the separatory funnel and contents over gently about six times, and allow the layers to settle and clear. Draw off the lower layer and discard. Wash the ether layer with 20 mL of water, shaking vigorously. Continue washing with 20 mL of KOH solution followed by 20 mL of water, shaking vigorously after each addition, until the alkali layer upon strong acidification with HCl and settling for a few minutes is only faintly opalescent. Finally wash the ether layer with 20-mL portions of water until the wash water is no longer pink to phenolphthalein.
40.1.6 Solvent Removal - Transfer the ether layer to a 150-mL beaker (counterbalance the beaker if the amount of unsaponifiable matter is small and important) and evaporate over a hot-water bath until practically free of ether. Heat the beaker at 75 to 80°C until constant weight is obtained.
NOTE 8 - A 30 % alcoholic solution by volume is the most satisfactory solution from which to extract the unsaponifiable matter.
NOTE 9 - If emulsions form, add 5 mL of alcohol, pouring it down the side of the funnel.
NOTE 10 - It is important to maintain the volume of ether at not less than 150 mL, otherwise small quantities of unsaponifiable matter may be lost.
NOTE 11 - To check whether or not the unsaponifiable matter is free from fatty acids, dissolve the residue in 10 mL of freshly boiled neutral alcohol and titrate with 0.1 N alcoholic KOH solution, using phenolphthalein as the indicator. Not more than 0.1 mL should be required for neutralization. If more is required, the determination has not been carried out effectively and must be repeated.
41. Calculation
41.1 Calculate the unsaponifiable matter as follows:
U = (R/G) x P
where:
U = unsaponifiable nonvolatile matter, %,
R = weight of residue, g,
G = weight of desulfated fatty matter, g, and
P = desulfated fatty matter, %
