for the difference in density of ocean water and fresh water due to a difference in the isotopic composition of oxygen yields 4.4 p.p.m., vide infra. 76, hence we can assume that the isotopic ratio in water remains constant as the above equilibrium is set up. There is, roughly, 10 3 times more oxygen in the water on the earth’s surface than in the whole atmosphere, as can be calculated from the data given by Longwell, Knopf and Flint, A Textbook of Geology (John Wiley and Sons, Inc., N.Y., 1932) and by Humphreys, Physics of the Air (McGraw‐Hill Book Co., New York, 1929), p. They had concluded that the initial change of density of the water on electrolysis was due more to the oxygen than to the hydrogen, not that α O >α H. Soc., 57, 2731 (1935) incorrectly stated that Washburn, Smith and Smith concluded that the oxygen isotopes fractionate more rapidly than those of hydrogen on electrolysis. Research 13, 599 (1934) Google Scholar CrossrefĮ. because of the low value of the fractionation factor for oxygen and therefore negligible. On calculation, however, this error was shown to be only 0.1 p.p.m. Smith has kindly pointed out to us that the difference in the isotopic composition of the air oxygen and water oxygen might not be the same after electrolysis as before because of a greater absolute electrolytic separation in the case of the air oxygen. This paper contains references to earlier work. Aston, Mass‐Spectra and Isotopes (Edward Arnold and Company, London, 1933), p. The chemical and physical standards of atomic weights are discussed and the proposal is made that a single standard based on the mass of a pure isotope such as protium be adopted. The distribution of oxygen isotopes in the atmosphere is calculated by means of the usual hypsometric equation, but the separation due to gravity is not sufficient to explain quantitatively the excess atomic weight of atmospheric oxygen. The difference in atomic weights can be accounted for quantitatively by assuming that an isotopic exchange equilibrium of the type discussed by Urey and Greiff occurs at a temperature of -50☌ in the lower regions of the stratosphere.
This observation finds experimental confirmation in the work of several other investigators and can be applied in certain cases to the reinterpretation of already existing data, clarifying several anomalous and inexplicable effects.
#Atomic mass of oxygen plus
A difference in the density of water made from atmospheric oxygen plus tank hydrogen and aqueous oxygen plus tank hydrogen is interpreted as indicating that the atomic weight of oxygen in the air is 0.000108 atomic weight units heavier than the oxygen of Lake Michigan water.
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