Accelerated Degradation Experiment
Conditions
Procedure A: |
30 days exposure at 50 °C and 100% relative humidity. |
Procedure B: |
30 days exposure at 50 °C and 100% relative humidity followed by 5 days at 70 °C and 100% relative humidity. |
Appearance of the material
The material, originally in the form of a shiny black, viscous liquid, changes after procedures A and B into a more viscous liquid due to the elimination of its volatile components.
Gain of moisture
A small loss of weight is observed after procedures A and B.
Chromatographic test
Adsorbent: Silica gel 60 F-254
Solution applied to the plate: Substance dissolved in methanol.
Solvent system:
light petroleum: ...........................95 volumes
acetic acid: ....................................5 volumes
Development conditions: The solvent is allowed to migrate until the front reaches a line 15 cm from the starting line.
Detection: The plate is examined under ultraviolet light at a wavelength of maximum output of about 254 nm and then at 365 nm.
Results: The reference solution of coal tar shows a series of spots more or less visible depending on the detection method. No changes occur in the chromatogram obtained from the solutions of each of the samples subjected to procedures A and B.
Gas-liquid chromatography
The chromatogram shows a great number of peaks (about 30) with little modification after procedures A and B, the intensities of the peaks changing with time.
Conclusion
Coal tar is subject to decomposition under accelerated degradation conditions.
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