Round Table Discussion. Direct Determination of Oxygen in Organic Compounds

Abstract

topic mixtures as test liquids, and indicated that preliminary experiments had been successful.Hawkins suggested a mixture of ethylbenzene and chlorobenzene as an ideal test mixture for columns with up to 80 plates, and also for tests a t both atmospheric and subatmospheric pressures.Its relative volatility ranges from 1.10 a t 760 mm. to about 1.12 at 20 mm. of mercury pressure. The use of an n-heptanemethylcyclohexane mixture a t reduced pressures was also suggested.F. E . Williams of Hercules Powder Go. pointed out the lack of test mixtures composed of compounds other than hydrocarbons. Rossini felt this was because hydrocarbons were more easily obtained in the pure state than other types of compounds. INTERPRETATION OF DATAWilliams pointed out the complexities of analyzing break cuts to obtain over-all composition, and the desirability of being able to calculate composition directly from the boiling point or refractive index curves. Schoenberger recommended the use of the equal-area cut-point method for low temperature distillations, but also indicated this method had definite limitations. Rossini observed that from accurate boiling points and vapor pressuretemperature curves it is possible to calculate the boiling point of an equimolar mixture and thus establish the cut point. The additional difficulties which result from the presence of a third component during the break were noted.Hawkins described the calibration of columns with known mixtures, in order to obtain arbitrary correction factors for locating cut points and account quantitatively for the material subjected to analytical distillation.

METHODS OF MICROANALYSIS, VIb OXYGEN DETERMINA TION; EVALUATION OF THE MAGNESIUM NITRIDE METHOD FOR FLUORINE-CONTAINING COMPOUNDS

“…3,4,8,9 Further data are given here to show that two atoms of fluorine in an organic compound give results nearly equivalent to one atom of oxygen. However, the results are not sufficiently reproducible to correct for fluorine found by analysis.…”

Direct Anaylsis of Oxygen-18 in Organic Compounds.

“…This work will be reported in the near future. it is possible to determine the cxygen- 1 8 content of many organic compounds without the need for chemical conversions and with a precision sufficient for most tracer and isotope-effect experiments, provided the tracer enrichment is about 5%.…”

“…suggested for analysis of isotopic composition of the oxygen in organic compounds, most involve the construction of relatively complex apparatus and none appears to be general and completely satisfactory (19). Doer-ing and Dorfman (6) adapted the Unterzaucher procedure for quantitative oxygen analysis (21,1,10) to the determination of oxygen-18 content and reported good results with a variety of compounds.…”