The quantitative determination of 2,6-ditertiary-butyl paracresol and 2,6-ditertiary-butyl phenol in a new electrical insulating oil measures the amount of this material that has been added to the oil as protection against oxidation. In a used oil it measures the amount remaining after oxidation has reduced its concentration. The test is also suitable for manufacturing control and specification acceptance.
When an infrared spectrum is obtained of an electrical insulating oil inhibited with either of these compounds there is an increase in absorbance of the spectrum at several wavelengths (or wavenumbers). 2,6 ditertiary-butyl paracresol produces pronounced increases in absorbance at 2.72 x03BC;m (3650 cmx2212;1), and 11.63 x03BC;m (860 cmx2212;1). 2,6 ditertiary-butyl phenol produces pronounced increases in absorbance at 2.72 x03BC;m (3650 cmx2212;1) and 13.42 x03BC;m (745 cmx2212;1).
When making this test on other than a highly oxidized oil or when using a double-beam spectrophotometer, it has been found convenient to obtain the spectrum between 2.5 x03BC;m (4000 cmx2212;1) and 2.9 x03BC;m (3450 cmx2212;1) because the instrument is compensated for the presence of moisture and the band is not influenced by intermolecular forces (associations). However, when testing a highly oxidized oil or when using a single-beam instrument better results may be obtained if the scan is made between 10.90 x03BC;m (918 cmx2212;1) and 14.00 x03BC;m (714 cmx2212;1).
Increased absorption at 11.63 x03BC;m (860 cmx2212;1) or 13.42 x03BC;m (745 cmx2212;1) or both, will identify the inhibitor as 2,6-ditertiary-butyl paracresol or 2,6-ditertiary-butyl phenol respectively (Note 1).
Note 18212;The absorbance at 745 cmx2212;1 for 2,6-ditertiary-butyl phenol and at 860 cmx2212;1 for 2,6-ditertiary-butyl paracresol for equal concentrations will be in the approximate ratio of 2.6 to 1.
1.1 This test method covers the determination of the weight percent of 2,6-ditertiary-butyl paracresol (DBPC) and 2,6-ditertiary-butyl phenol (DBP) in new or used electrical insulating oil in concentrations up to 0.5 % by measuring its absorbance at the specified wavelengths in the infrared spectrum.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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