Stable isotope studies. Annual progress report, December 1, 1978-November 30, 1979

Technical Report · Fri Dec 14 04:00:00 EST 1979

OSTI ID:5772915

Ishida, T

The BBIR-Type precision cryostat was debugged, and interfacing of the cryostat with an LSI-11-based microcomputer was completed. A program for the cryostat control and data acquisition was written. A spiral quartz gauge for the absolute pressure measurements up to 1500 torr has been calibrated against a dead-weight gauge. The vapor pressures of /sup 12/CHF/sub 3/, /sup 13/CHF/sub 3/, and /sup 12/CDF/sub 3/ have been measured in the cryostat at temperatures between -139.85/sup 0/C and -80.81/sup 0/C. The carbon isotope effects observed are inverse effect, i.e., P(/sup 13/C) > P(/sup 12/C), while the hydrogen isotope effect observed are normal effect, P(H) > P(D). The observed carbon vapor pressure isotope effects point to a second cross-over temperature at 218.66/sup 0/K, at which P(/sup 13/C) = P(/sup 12/C). A plot of T 1n(P'/P) against 1/T for the observed D/H vapor pressure isotope effects indicates a positive intercept with the ordinate. These anomalies are explainable on the basis of the blue-shift in the C-H stretching frequency in fluoroform. Besides the isotopic species of fluoroform, methylfluoride was also purified to reduce all chemical impurities to a level below 10 ppM. The construction of nitrogen-15 fractionation system using gaseous nitric oxide under pressure and liquid dinitrogen trioxide, which was started during 1978, was continued. A new scheme for the determination of unit stage separation factor (..cap alpha..) for isotope exchange reactions has been devised,which combines the advantages of the cascade method and the single-stage method. An analytical expression has been developed for the effect of a differential change in a vibrational force constant upon isotopic reduced partition function ratio.

• Research Organization: City Univ. of New York, NY (USA)
• OSTI ID: 5772915
• Report Number(s): COO-3127-31
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400203 -- Isotope Exchange & Isotope Separation-- (-1987)
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
CARBON 13
CARBON ISOTOPES
CHALCOGENIDES
DEUTERIUM
EVEN-ODD NUCLEI
FLUORINATED ALIPHATIC HYDROCARBONS
FLUOROFORM
FUNCTIONS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
NITRIC OXIDE
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN ISOTOPES
NITROGEN OXIDES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PARTITION FUNCTIONS
PHYSICAL PROPERTIES
RESEARCH PROGRAMS
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
VAPOR PRESSURE