ASTM D500 Test Methods of Chemical Analysis of Sulfonated and Sulfated Oils
INORGANIC SALTS
42. Scope
42.1 This test method covers the determination in a sample of sulfonated or sulfated oil, or both, the inorganic sulfates, chlorides, and all other salts that are insoluble in a mixture of oleic acid and chloroform.
43. Apparatus
43.1 Either a Gooch crucible or filter paper may be used for filtering. Ignite the Gooch crucible in a larger crucible, supported by an asbestos ring and assembled as shown in Fig. 3. If filter paper is used, it may be a 9-cm general purpose ashless filter paper.
43.2 Thermometer.
44. Reagents
44.1 Chloroform (CHCl3).
44.2 Ethyl Ether.
44.3 Oleic Acid.
45. Procedure
45.1 The procedure consists of dehydrating the sample, dissolving in a solvent, filtering, igniting, and weighing the residue. In the presence of ammonium salts, the residue is not ignited but only dried to constant weight. The presence of sodium acetate does not interfere with this method.
45.1.1 In the Absence of Ammonium Salts - Weigh 3 to 5 g of the sample and place in a 250-mL beaker, add an approximately equal amount of oleic acid, and heat the mixture on an oil bath, while stirring constantly with a thermometer, at a temperature of 105 to 110°C until practically free from water. Continue the heating until the temperature of the contents reaches 118 to 120°C and maintain at that temperature for about 5 min. If the dehydrated sample upon cooling does not remain liquid, add more oleic acid. Dissolve the dehydrated sample in 100 mL of CHCl3 warmed to 50 to 55°C and filter through a counterpoised filter paper or a Gooch crucible. Prepare the Gooch crucible by passing a thin emulsion of alkali- and acid-washed asbestos fiber in water through the crucible until a pad of about 2 mm in thickness is formed. Dry the asbestos pad and ignite for 30 min at first gently and finally more strongly. Then pass 75 mL of CHCl3 through the crucible and again ignite the asbestos pad, cool in a desiccator, and weigh. Repeat the process of washing with CHCl3 until there is no further loss in weight. Wash the residue with three 15-mL portions of a solution of oleic acid in CHCl3 (2 %), then with six 15-mL portions of hot CHCl3, and finally with two 15-mL portions of ether or until the residue is free from oil. Take care that the top of the filter is thoroughly washed. Transfer the last traces of the residue to the filter by allowing the solvent to evaporate when the salts become free flowing. Dry the residue at 125 to 130°C for 45 min, cool in a desiccator, and weigh. Ignite the residue at a dull red heat for 15 min, weigh, and repeat the ignition until constant weight is obtained.
45.1.2 In the Presence of Ammonium Salts - Proceed as described in 45.1.1 for the determination of inorganic salts in the absence of ammonium salts with the following exceptions: (1) in preparing the Gooch crucible, do not ignite but heat it at 105 ± 2°C for 45 min and repeat the heating until constant weight is obtained, and (2) heat the residue, whether in a Gooch crucible or on a filter paper as in (1) but do not ignite it.
46. Calculation
46.1 The method of calculation depends upon whether or not ammonium salts are present in the sample.
46.1.1 Calculate the inorganic sulfates and chlorides including ammonium salts as follows:
Inorganic sulfates and chlorides, including ammonium salts, % = (A/B) x 100
where:
A = weight of dried residue, g, and
B = weight of sample, g.
46.1.2 Calculate the nonvolatile inorganic sulfates and chlorides (in the absence of ammonium salts) as follows:
Nonvolatile, inorganic sulfates and chlorides; % = (A/B) x 100
where:
A = weight of ignited residue, g, and
B = weight of sample, g.
NOTE 12 - In the absence of ammonium salts, the difference between the percentage of the dried residue and the percentage of the ignited residue shall not be greater than 0.25 %.
