FOR IMMEDIATE RELEASE:             Roger Rensberger
July 22, 1994                      (301) 975-2762

                                   TN-5984

                   PC DATABASE AVAILABLE FOR PREDICTING

                  THERMOCHEMICAL PERFORMANCE OF MATERIALS


     Chemical manufacturers, material suppliers, and researchers
in science and industry now have an easy-to-use computer program
for help in predicting the performance of chemicals in their
custody, including storage, shipping, and use in the laboratory
and in manufacturing.  The personal computer database, Chemical
Thermodynamic and Energy Release Program, known as CHETAH, is
available from the National Institute of Standards and
Technology.

     CHETAH, Version 7.0, is an important tool for estimating
both thermochemical properties and predicting certain
"reactivity" hazards associated with a pure chemical, mixture of
chemicals or a chemical reaction.  The program is designed to
conveniently and accurately calculate properties such as heat
capacity, enthalpy, entropy and Gibbs energy of reactions as a
function of temperature at 298.15 kelvin.

     Malcolm W. Chase, chief of the SRDP at NIST, says this is
accomplished through a knowledge of only the molecular structure
of the components involved by an implementation of the well-known
Benson's second order group additivity method for gases, and
through ionic group additivity for inorganic solids.  The
thermochemical estimation part of the program is currently not
capable of handling organic solids or liquids, Chase adds.

     There is an "energy release evaluation" option that provides
the user with information about the ability of a material to
decompose with violence if subjected to severe impact.  Among
other functions in CHETAH are the ability to build compounds from
library or user-entered groups, gases or solid crystals; build
crystals from ionic groups; enter private thermochemical data;
and classify mixtures for flammability and estimate lower
flammable limits for a substance.

     The CHETAH computer program was developed originally by a
group of researchers and scientists in the American Society for
Testing and Materials' Committee E-27 on Hazardous Potential of
Chemicals.  ASTM asked NIST to review and evaluate the product
and make it available to the public through the institute's
widely known Standard Reference Data Program.

     Since 1968, the NIST program has been responsible, under 
an act of Congress, for coordinating the evaluation of numerical
data that describe the chemical and physical properties of 
well-defined substances.

     NIST Special Database 16:  CHETAH, Chemical Thermodynamic
and Energy Release Program, Version 7.0, is available for $350. 
It is designed for any MS DOS or PC DOS computer using DOS 2.1 or
greater and at least 512 KB memory.

     To order CHETAH, Version 7.0, contact the Standard Reference
Data Program, A320 Physics Building, NIST, Gaithersburg, Md.
20899-0001, (301) 975-2208, fax:  (301) 926-0416, e-mail: 
SRDATA@enh.nist.gov (via Internet).

     As a non-regulatory agency of the Commerce Department's
Technology Administration, NIST promotes U.S. economic growth 
by working with industry to develop and apply technology,
measurements and standards.

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