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Clean and dry the apparatus. Deliver 10 milliliters of aniline-- warning, see 7.1 of the written standard-- and 10 milliliters of the dried sample, 8.1 of the written standard, into the tube fitted with pump stirrer and thermometer. If the material is too viscous for a volumetric transfer, weigh to the nearest 0.01 gram a quantity of sample corresponding to 10 milliliters at room temperature. Place the thermometer in the tube so that the contraction chamber is below the liquid level and so that the mercury bulb does not touch the side of the tube. Assemble the apparatus as shown in figure A2.2 of the written standard. Adjust the speed of the pump to produce a continuous stream of the oil aniline mixture in the form of a thin film flowing over the light well. With extremely dark oils, operate the pump slowly and lower it so that the delivery tube nearly touches the top of the light well, so as to obtain a continuous film thin enough to permit observation of the aniline point. Adjust the voltage on the lamp until just enough light is given for the filament to be visible through the film. Raise the temperature of the mixture at a rate of 1 to 2 degrees Celsius, 2.0 to 3.5 degrees Fahrenheit per minute, until the aniline point has just been passed, as denoted by a definite sudden brightening of the lamp filament and by the disappearance of the more or less opalescent condition of the film. Note A2.1 of the written standard. Discontinue heating and adjust the lab voltage so that the filament appears clear and distinct but not uncomfortably bright to the eye. Adjust the temperature of the bath so that the sample aniline mixture cools at a rate of 0.5 to 1.0 degrees Celsius, 1.0 to 1.8 degrees Fahrenheit per minute, and note the appearance of the film and light filament. Record as the aniline point the temperature at which a second phase appears, as evidenced by the reappearance of the opalescent condition of the film, usually causing a halo to appear around the lamp filament or by a sudden dimming of the lamp filament, or both. At temperatures above the aniline point, the edges of the light filament appear clear and distinct. At the aniline point temperature, a halo or haze forms around the filament, replacing the distinct lines of the filament edge with lines that appear cloudy or hazy in appearance. Further darkening of the cloud over the filament occurs at lower temperature but is not to be confused with the aniline point. For those making the test for the first time, the following procedure may be helpful. Make preliminary operational adjustments and test using a colorless sample aniline mixture and observe changes taking place in the body of the liquid in film. Make rough tests with dark oils to become familiar with the appearance of the film and light source, as the mixture passes from the clear state above the aniline point to the translucent state below. If the sample is such that there is difficulty in observing the exact point of the phase change, make experiments with the sample using various intensities of light and paying particular attention to the appearance of the light in the immediate vicinity of the lamp filament. Repeat the observation of aniline point temperature by heating and cooling repeatedly until the report, as directed in section 11 of the written standard, can be made.

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Duration: 4 minutes and 9 seconds
Language: English
License: Dotsub - Standard License
Genre: None
Views: 5
Posted by: abuckmaster on Sep 14, 2018


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