D611_A1.2

Clean and dry the apparatus. Deliver 10 milliliters leaders of aniline-- warning, see 7.1-- and 10 milliliters of the dried sample, 8.1, into the test tube fitted with a stirrer and thermometer. If the material is too viscous for volumetric transfer, weigh to the nearest 0.01 gram a quantity of the sample corresponding to 10 milliliters at room temperature. Center the thermometer in the test tube so that the immersion mark is at the liquid level, making sure that the thermometer bulb does not touch the side of the tube. Center the test tube in the jacket tube. Stir the mixture rapidly, using a 50 millimeter-- 2 inch-- stroke, avoiding the introduction of air bubbles. If the aniline sample mixture is not miscible at room temperature, apply heat directly to the jacket tube so that the temperature rises at a rate of 1 to 3 degrees Celsius-- 2 to 5 degrees Fahrenheit-- per minute by removing or reducing the heat source until complete miscibility is obtained. Continue stirring and allow the mixture to cool at a rate of 0.5 to 1.0 degrees Celsius-- 1.0 to 1.8 degrees Fahrenheit-- per minute. Continue cooling to a temperature of 1 to 2 degrees Celsius-- 2.0 to 3.5 degrees Fahrenheit-- below the first appearance of turbidity and record as the aniline point the temperature at which the mixture suddenly becomes cloudy throughout. Note A1.1. This temperature and not the temperature of separation of small amounts of material is the minimum equilibrium solution temperature. The true aniline point is characterized by a turbidity that is so cloudy as to obscure the thermometer bulb in reflected light. If the aniline sample mixture is completely miscible at room temperature, substitute a non-aqueous cooling bath for the heating source. Allow to cool at the rate specified in A.1.2.2 and determine the aniline point as described. Repeat the observation of aniline point temperature by heating and cooling repeatedly until a report as directed in section 11 can be made.