6. Apparatus
6.1 Foaming Test Apparatus, an example of a suitable set-up is shown in Fig. 1, consisting of a 1000-mL graduated cylinder or cylinders held in position when placed in the baths, such as fitted with a heavy ring or clamp assembly to overcome the buoyancy, and an air-inlet tube, to the bottom of which is fastened a gas diffuser. The gas diffuser can be either a 25.4-mm (1-in.) diameter spherical gas diffuser stone made of fused crystalline alumina grain, or a cylindrical metal diffuser made of sintered five micron porous stainless steel (Note 1). The cylinder shall have a diameter such that the distance from the inside bottom to the 1000-mL graduation mark is 360 more or less 25 mm. It shall be circular at the top (Note 2) and shall be fitted with a stopper, such as those made of rubber, having one hole at the center for the air-inlet tube and a second hole off-center for an air-outlet tube. The air-inlet tube shall be adjusted so that, when the stopper is fitted tightly into the cylinder, the gas diffuser (Note 3) just touches the bottom of the cylinder and is approximately at the center of the circular cross section. Gas diffusers shall meet the following specification when tested in accordance with the method given in Annex A1:
NOTE 1 - Gas diffuser permeability and porosity can change during use; therefore, it is recommended that diffusers be tested when new and periodically thereafter preferably after each use.
NOTE 2 - Graduated cylinders with circular tops can be prepared from cylinders with pouring spouts by cutting them off below the spouts. The cut surface is to be smoothed before use by fire polishing or grinding.
NOTE 3 - Gas diffusers may be attached to air-inlet tubes by any suitable means. A convenient arrangement is shown in Fig. 2.
6.2 Test Baths, large enough to permit the immersion of the cylinder at least to the 900-mL mark and capable of being maintained at temperatures constant to 0.5°C (1°F) at 24°C (75°F) and 93.5°C (200°F), respectively. Both bath (Note 5) and bath liquid shall be clear enough to permit observation of the graduations on the cylinder.
NOTE 4 - Air baths may also be utilized for heating purposes. Limited data has shown that both liquid and air baths give equivalent results. However, the precision estimates given in Section 13 are based on using only liquid baths.
NOTE 5 - Heat-resistant cylindrical glass jars approximately 300 mm (12 in.) in diameter and 450 mm (18 in.) in height make satisfactory baths.
6.3 Air Supply, from a source capable of maintaining an air flow rate of 94 more or less 5 mL/min through the gas diffuser. The air shall be passed through a drying tower 300 mm in height packed as follows: just above the constriction place a 20-mm layer of cotton, then a 180-mm layer of indicating desiccant, and a 20-mm layer of cotton. The cotton serves to hold the desiccant in place. Refill the tower when the indicating desiccant begins to show presence of moisture. A flowmeter sensitive to the required tolerances can be used to measure the air flow (Note 6).
NOTE 6 - A manometer type flowmeter, in which the capillary between the two arms of the U-tube is approximately 0.4 mm in diameter and 16 mm in length, and in which n-butylphthalate is the manometric liquid, is suitable.
6.3.1 The total volume of air leaving the foaming test apparatus shall be measured by a volume measuring device (Note 8) capable of accurately measuring gas volumes of about 470 mL. The air shall be passed through at least one loop of copper tubing placed around the inside circumference of the cold bath so that the volume measurement is made at approximately 24°C (75°F). Precautions are to be taken to avoid leaks at any point in the system.
NOTE 7 - Alternatively, a 1 L cylinder (with 10 mL graduation marks) full of water is inverted in a tall, large beaker also filled with water. There should be no air bubbles inside. Air leaving the copper loop in the bath is connected below the cylinder. When the test is started, air will flow into the cylinder, displacing the water. At the end of the test, the volume of air in the cylinder is measured by equalizing the water levels inside and outside the cylinder. Alternatively, the total volume of air passed would be the difference between the final and the initial volumes of water in the cylinder.
NOTE 8 - A wet test meter calibrated in hundredths of a litre is suitable.
6.4 Timer, graduated and accurate to 1 s or better.
6.5 Thermometer, having a range as shown below and conforming to the requirements as prescribed in Specification E1 or specifications for IP thermometers:
7. Reagents and Materials
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all cases. Unless indicated otherwise, it is intended that all reagents conform to the specifications of the committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
7.2 Acetone - (Warning - Extremely flammable, vapors can cause a flash fire).
7.3 Compressed Air, hydrocarbon free and dry to a dew point of -60°C or lower.
NOTE 9 - If the source of compressed air is ensured to the stated specifications, the drying tower in 6.3 may not be necessary.
7.4 Heptane - (Warning - Flammable, vapor harmful).
7.5 Propan-2-ol - (Solvents with equivalent cleaning and solvency characteristics may be substituted for propan-2-ol.)
7.6 Toluene (Methylbenzene) - (Solvents with equivalent cleaning and solvency characteristics may be substituted for toluene.)
8. Hazards
8.1 (Warning - Users of this test method shall be trained and familiar with all normal laboratory practices, or under the immediate supervision of such a person. It is the responsibility of the operator to ensure that all local legislative and statutory requirements are met.)
8.2 (Warning - Cleaning solvents have flash points lower than ambient temperatures. Avoid the possibility of fire or explosion.)
8.3 (Warning - The fumes from the test oil and the bath shall be vented in a manner compatible with local government regulations.)
8.4 (Warning - Some apparatus assemblies can have as much as 20 L of heat transfer oil at 93.5°C. Therefore, in the event of breakage of the containing vessel, provisions for suitable containment of the spill is advisable.)