Care must be taken to ensure adequate insulation in the selection of switches Sc, S29 S3, S4, and Si. INDUSTRIAL AND ENGINEERING CHEMISTRYVol. 40, No. 1 300 ml. of natural sea water. This sea water had a pH of 8 and was filtered before use. A No. 30 cork stopper with a hole for the coated rod and another for the reference electrode bridge was used in each jar. The reference half-cell contained Hg, HgGl, and sea water in the flask, and an agar-sea water gel in

Polyethylene can be heat‐oxidized in air when temperatures in excess of 125°C. are employed or photo‐oxidized when exposed to ultraviolet radiation during weathering. Infrared spectrophotometric studies show that during these types of oxidation carbonyl groups are formed and the concentrations of the three types of carbon to carbon double bond groups present are altered. Grating spectra in the 5.6–6.0 micron region reveal that the carbonyl groups formed by heat‐oxidation are mainly ketonic (5.81 microns) although some aldehyde (5.77 microns) and acid (5.84 microns) groups are also present. In photo‐oxidized samples, the carbonyl groups are rather well distributed among the aldehyde, acid and ketone forms. For oxidized samples showing intense carbonyl absorptions, there is a small increase in the concentration of RHCCHR groups (10.35 microns) for both types of oxidation. At this same degree of oxidation both the heat‐and photo‐oxidized samples show decreases in the concentration of RRCCH2 groups (11.25 microns). However, this decrease is considerably more pronounced in the photo‐oxidized samples. Finally, there is a small decrease in the concentration of RHCCH2 groups (10.07 and 11.00 microns) in the heat‐oxidized samples which stands in contrast to a large increase in concentration of RHCCH2 groups produced by photo‐oxidation. The presence of an absorption maximum at 2.81 microns as the heat‐oxidation of polyethylene is occuring is indicative of unstable hydroperoxide groups.

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A series of polyethylene resins made by making progressive changes in temperature, pressure, and catalyst content has been studied by infrared absorption spectroscopy. From the methyl content and the number‐averages molecular weight of each resin, it was found that as molecular weight increases degree of branching decreases. Also revealed was the fact that each of the three types of double bond groups present, i. e., RHCCH2, RHCCHR, and RRCCH2, decreases in concentration with increasing molecular weight. Using polarized radiation, high resolution grating spectra were obtained on polyethylene films which had been highly oriented by cold drawing 500%. The results show that the CH3 terminated branches are not predominantly oriented either parallel or perpendicular to the direction of stretch. It is the authors' view that the chain branches vary in length with a considerable fraction short enough to be essentially at right angles to the long chain axis while others are sufficiently long to be parallel to the long chain axis in stretched polyethylene. When a stretched polyethylene film is heat relaxed (110–115°C.), its spectra using polarized radiation reveal the presence of crystallites in which the long carbon‐to‐carbon chain axes are predominantly oriented at right angles to the direction of stretch.

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