![]() Thus in the event of a diaphragm failure there was no chance of high pressure oxygen coming in contact with the oil. The second separated the nitrogen from the oxygen sample. The first separated the oil in the gage from an intermediate nitrogen gas system. The oil operated dead-weight gage pressure measuring system was modified, as shown in figure 1 here, for safety. For measurements above 200 K the only refrigerant used was the liquid nitrogen in the open dewar surrounding the cryostat. For the high temperature ( T >150 K) portion of the measurements the shield, shown in figure 2 of reference, was replaced with one that completely surrounded the sample holder thereby reducing heat losses to the cold wall. Jacketing the capillary with 1 8 in OD copper tubing removed this difficulty. Early vapor pressure measurements yielded results which were lower than published values by 4000 to 6000 N/m 2, indicating the presence of a cold spot in the stainless steel transition capillary which connects the sample holder to the top of the cryostat. These modifications are listed below in terms of the nomenclature used in reference. The cryostat designed and described by Goodwin was used with minor modifications. ![]() A more complete set of tables will be issued as NBS Tech. The properties calculated using this smoothed surface are compared with some of the P–V–T and thermodynamic property data from the literature.ĭue to limitations of space only skeleton tables of thermodynamic properties are presented here. Thermodynamic calculations for the compressed liquid at subcritical temperatures made use of additional data in the form of new experimental determinations of the heat capacity at constant volume and heat capacity of the saturated liquid from this laboratory. This representation of the P–V–T surface together with the specific heat of the ideal gas allowed the calculation of thermodynamic properties of the gas at temperatures below critical and of all densities at temperatures above critical. Second and third virial coefficients were extracted from the low density data. The highest and lowest density data were represented by two analytic surfaces while the intermediate densities were fitted to a large number of isotherm polynomials. The data range in pressure up to about 33 MN/m 2. The data range from the triple point temperature to 300 K for the high densities and from 85 K to 300 K for the low (subcritical) density points. ![]() This constitutes approximately two-thirds of all the P–V–T data published for oxygen. The results of the present investigation consist of approximately 1500 P–V–T points at 111 different densities varying from 0.0047 to 3 times the critical density. However, these results were limited in scope and there was disagreement in the region in which they overlapped. In 19 Timrot and Borisoglebskii 1 and Van Itterbeek and Verbeke published new P–V–T results for the liquid. This condition was especially true for the compressed liquid. Prior to 1960 there were relatively few measurements of the P–V–T properties of oxygen at low temperatures. The results of part of that program are presented here in the form of extensive tables of P–V–T data and derived thermodynamic properties. space program and the lack of comprehensive and accurate data for many of its physical properties have led to an extensive research program at the NBS Institute for Basic Standards.
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