Oxygen absorption excess

The behaviour of an antioxidant in a closed system (in an oxygen absorption test) is dominated by different physical characteristics. Table 4 demonstrates a general relationship between antioxidant effectiveness and solubility in a hydrocarbon solvent suggesting that antioxidant solubility in the polymer can be critical in certain applications. In the case of low molecular weight antioxidants with low solubility and high mobility, the excess blooms to the surface where it is ineffective as a stabilizer and is aesthetically objectionable. The solubility of a series of antioxidants which contain the same... 

Discussion. Molybdenum(VI) in acid solution when treated with tin(II) chloride [best in the presence of a little iron(II) ion] is converted largely into molybdenum(V) this forms a complex with thiocyanate ion, probably largely Mo(SCN)5, which is red in colour. The latter may be extracted with solvents possessing donor oxygen atoms (3-methylbutanol is preferred). The colour depends upon the acid concentration (optimum concentration 1M) and the concentration of the thiocyanate ion (1 per cent, but colour intensity is constant in the range 2-10 per cent) it is little influenced by excess of tin(II) chloride. The molybdenum complex has maximum absorption at 465 nm. 

The oxidation of N, A-dimethylaniline by aerated, ethanolic cupric chloride to give a mixture of products including methyl and crystal violets is simple second-order when an excess of amine is used Presumably Cu(I) is re-oxidised by dissolved oxygen, for otherwise the observed linearity of log [residual amine] versus time plots would not be found as Cu(II) disappears. Under nitrogen the kinetics are complex, but a new optical absorption (472 and 1007 nm) appears immediately on mixing the reactants. This absorption decays whilst a new one at 740 nm develops. The latter absorption originates from a 1 1 complex formulated... 

The rate of absorption of oxygen by liquid butenyne increased with time, and eventually a yellow liquid phase separated. After evaporation of excess hydrocarbon, the yellow peroxidic liquid was explosive. Presence of 5% of chloroprene... 

Rising above the background emission, assumed to be that of a blackbody at 3000°K, is a broad 9.7-jam feature for the oxygen star. Between about 15 and 20 jim a much weaker excess emission feature is also evident. A measured absorption spectrum of amorphous olivine smoke particles (Kratschmer and Huffman, 1979) is shown for comparison. 

Dust around the carbon star shows an excess emission feature between about 10.2 and 11.6 jam, clearly distinguishable in both shape and position from the 9.7-jum feature of the oxygen star, which has been attributed to small SiC particles. These particles cannot be spherical, however. According to the discussion in Section 12.2, shape effects spread an absorption band in small particles of materials like SiC between the transverse (to,) and longitudinal (to,) optical mode frequencies these frequencies for SiC are indicated on the figure. This point was made by Treffers and Cohen (1974) using Gilra s unpublished calculations. To illustrate this further, calculations for a random distribution of... 

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