ASTM D6 standard test method for loss on heating of oil and asphaltic compounds
5. Apparatus
5.1 Oven - The oven shall be electrically heated and shall conform to the performance requirements of Specification E 145 Type I, Grade B, for operating temperatures up to 180°C (365°F). During the tests for compliance to Specification E 145 requirements, the oven shelf, properly placed shall be in place and rotating. In addition, it shall also comply with the following requirements:
5.1.1 Construction (Note 1) - The oven shall be rectangular with minimum interior dimensions of 330 mm (13 in.) in each direction. The oven shall have in front a tightly fitting hinged door, which shall provide a clear opening substantially the same as the interior height and width of the oven. The door may contain a window with dimensions of at least 100 by 100 mm (4 by 4 in.), and with two sheets of glass separated by an air space, through which a vertical thermometer located as specified in Section 8, may be read without opening the door; or the oven may be provided with an inner glass door, through which the thermometer may be observed on opening the outer door momentarily. The oven shall be adequately ventilated by convection currents of air and for this purpose shall be provided with openings for the entrance of air and for the exit of heated air and vapors. Openings may be of any size and arrangement provided the requirements of Specification E 145, Type I, Grade B, are met.
5.1.2 Rotating Shelf - The oven shall be provided with a circular metal shelf having a minimum diameter of 250 mm (9.8 in.). (A recommended form of aluminum shelf is shown in Fig. 1.) The shelf shall be suspended by a vertical shaft and centered with respect to the horizontal interior dimensions. The shelf shall be provided with a mechanical means of rotating it at the rate of 5 to 6 rpm. The shelf shall be vertically located as close to the center of the oven as permitted by compliance with the requirements of 7.2 regarding thermometer placement.
NOTE 1 - Continued use of existing smaller ovens complying with the requirements of this test shall be permitted for an indefinite period to provide for normal amortization of present equipment. However, all new ovens purchased should comply with the minimum dimensions and requirements of this test method.
5.2 Thermometer - An ASTM Loss on Heat Thermometer graduated in Celsius degrees, having a range from 155 to 170°C and conforming to the requirements for Thermometer 13C as prescribed in the Specification E 1.
5.3 Container - The container in which the sample is to be tested shall be of metal or glass, cylindrical in shape, and shall have a flat bottom. Its inside dimensions shall be substantially as follows: diameter, 55 mm (2.17 in.), depth, 35 mm (1.38 in.).
NOTE 2 - Containers known in the drug trade as seamless "ointment boxes" may be obtained in dimensions conforming to the above requirements.
6. Technical Hazards
6.1 Under ordinary circumstances a number of samples having about the same degree of volatility may be tested at the same time. Samples varying greatly in volatility should be tested separately. When extreme accuracy is required not more than one material should be tested at one time and duplicate samples of it should be placed simultaneously in the oven. Such duplicates shall check within the limits of accuracy given in Section 9. Results obtained on samples showing evidences of foaming during the test shall be rejected.
7. Preparation of Sample
7.1 Thoroughly stir and agitate the sample as received, warming, if necessary, to obtain a complete mixture before the portion for analysis is removed.
7.2 First test the material under examination for water and, if water is present, remove it by suitable methods of dehydration before subjecting the material to the loss on heating test; or, obtain another sample that is free of water.
