ASTM D500 Test Methods of Chemical Analysis of Sulfonated and Sulfated Oils
TOTAL ACTIVE INGREDIENTS
33. Scope
33.1 This test method covers the determination of the total active ingredients in a sample of sulfonated or sulfated oil, or both, as it exists in the original sample by extracting the undecomposed sulfonated or sulfated fat and other fatty matter over an acidified concentrated salt solution. Free alkali or alkali bound as soap is not included.
NOTE 5 - In the case of sulfated oils only, this determination may also be estimated by calculation (see 36.3), as it is equivalent to the sum of the desulfated fatty matter and neutralized organically combined sulfuric anhydride.
34. Reagents
34.1 Ethyl Ether.
34.2 Methyl Orange Indicator Solution (1 g/L) - Dissolve 0.1 g of methyl orange in 100 mL of water.
34.3 Sodium Chloride (NaCl), solid.
34.4 Sodium Sulfate (Na2SO4), anhydrous.
34.5 Potassium Hydroxide, Alcoholic Standard Solution (0.5 N) - Accurately prepare and standardize a 0.5 N alcoholic potassium hydroxide (KOH) solution the strength of which shall be expressed as milligrams of KOH per millilitre; 1 mL of 0.5 N alcoholic KOH solution is equivalent to 28.05 mg of KOH.
35. Procedure
35.1 The procedure consists of isolating and purifying the fatty matter as it exists in the original oil by dissolving the sample in a solvent, acidifying and washing with saturated brine, and weighing the purified extract. Proceed as described in the determination of organically combined sulfuric anhydride, Test Method C, in the absence of ammonia (27.1.1), retaining the separated active ingredients in the 150-mL beaker instead of transferring it to a crucible. Evaporate the filtrate to a total volume of about 20 mL, add exactly 2 mL of alcoholic KOH solution, mix the contents by swirling, and finally evaporate until practically free from ether.
NOTE 6 - With highly sulfonated or sulfated oil, it may be necessary to add 5 to 10 mL of the alcoholic KOH solution in order to stabilize the residue.
35.2 Dry the residue at 108 to 112°C for 1 1/2 h, cool in a desiccator, and weigh. Repeat the heating for 30-min periods until constant weight is obtained.
36. Calculation
36.1 Correction for the Alkali Added - Calculate the correction for the alkali added as follows:
Correction for alkali added, g = 0.0006791 AS
where:
A = millilitres of KOH solution added,
S = strength of KOH solution, mg of KOH/mL, and
0.0006791 = molecular ratio of (K - H): KOH divided by 1000.
36.2 Total Active Ingredients - Calculate the total active ingredients as follows:
Total active ingredients, % = [(B - C)/D] x 100
where:
B = weight of residue, g,
C = alkali correction, and
D = weight of sample, g.
36.3 Total Active Ingredients Calculation Method (for Sulfated Oils Only) - Calculate the total active ingredients by the calculation method that is applicable to sulfated oils only, as follows:
T = P + [(NaSO4`/SO3) x Y]
or
T = P + 1.4875 x Y
where:
T = total active ingredients, %
P = total desulfated fatty matter, %, and
Y = percentage of combined SO3.
NOTE 7 - The factor 1.4875 is based on the assumption that the desulfated fatty matter becomes polymerized at the point where the SO3 splits off and no hydroxyl groups are formed. If the latter are formed the factor becomes (NaSO3 - 1)/SO3 = 1.275.
Calculated results were in better agreement with actual determinations when the higher factor was used.
