output of the thermodynamic functions Cp, S, G, H, Phi = (G H)/T and
Beta = G/RTln10, for temperatures specified by the user for pure
substances and chemical reactions. The output can be produced in
tabular or graphical form, and may be displayed on the screen or saved
in a file. Graphical output can be sent to a local plotting device such
as a laser printer.
produce plots and tabulations, data for the substance(s) are
retrieved from one or more databases and the appropriate calculations
performed. The databases available will depend on the particular
installation. They may include:
substance database from
Scientific Group Thermodata Europe (SGTE)
TPPS Based on the publications
of the Institute for High Temperatures (Moscow)
CSIRO A database provided by the
Commonwealth Scientific and Industrial Research Organisation, Australia
there are several substances under consideration (for example,
when a chemical equation has been entered), data for each substance may
be retrieved from a different database, specified by the user.
Facilities exist within the program for amending existing data and
saving them into a user defined database: the reference databases
supplied with MTDATA are protected against corruption.
Brief summary of commands
The parameters set by AUTOBALANCE control the way in which an equation
is automatically balanced. Note that the AUTOBALANCE command does not
itself balance the equation balancing is invoked by DEFINE, USE or
DEFINE allows the user to enter the SUBSTANCE formula or
chemical EQUATION for which thermodynamic functions are required. If
the entry is a chemical equation (including an equals sign), it is
first balanced and then data for all substances present are retrieved
from the default database.
STATUS displays the current status of parameters, such as
the current equation and units, the default database, and the
temperature and pressure lists.
USE_DATABASE searches a specified database in order to retrieve
data for a named substance; it can also be used to change to another
SET this command has two different purposes:
(a) it is used to specify one, or a series of
temperatures for which thermodynamic functions are calculated and
displayed by GO.
(b) it defines which thermodynamic functions are to
be calculated and tabulated by GO.
STEP defines a series of temperatures for which
thermodynamic functions are calculated and displayed by GO. STEP is a
more convenient method then SET of specifying a series of more than
PLOT is used to define the variables to be plotted, and
the labelling and scaling of the plot.
TABULATE controls the destination to which tabular output
is sent when the GO command is issued. It also allows a title to be
attached to the table.
AMEND allows the user to edit the equation or substance
SAVE_DATA incorporates data that has been assessed and
amended by means of THERMOTAB into a database specified by the user.
LIST displays on the screen the thermodynamic data held
in memory, as they have been retrieved from the database (and possibly
QUANTIFY allows the user to alter the units of energy and
GO converts the thermodynamic data retrieved from the
database into the thermodynamic functions specified in SET FORMAT
and/or PLOT, and sends them to the terminal or file.
RETURN takes the user out of THERMOTAB
back to the module level.
runs a macro taken from a file. The name of the file should be
entered in quotes. Commands can also be passed through to the
operating system by prefixing them with a $ (dollar sign). The
dollar sign and operating system command should be entered within
The principles of the
operation of the help system within MTDATA are given elsewhere. The purpose
of the following is to draw attention to difficulties faced by users
new to THERMOTAB. For the beginner nothing can be
more frustrating than cryptic messages, which are difficult to
interpret. This section provides two examples of situations in which,
because THERMOTAB is not a human with chemical
knowledge, the messages produced by THERMOTAB are
not all they seem.
THERMOTAB OPTION? define
H2 NOT FOUND IN SGSUB
When substance(s) are
entered using the DEFINE option, the default database is searched to
retrieve the data. The NOT FOUND IN message means that the data are not
present on the currently selected database in this case SGSUB. It seems
strange that such a common substance is not on the database, until it
is realised that the state of matter symbol has been
omitted. The program will not point this out, because it takes an
omission to indicate the default state . It does not know
that hydrogen has rather a low boiling point.
THERMOTAB OPTION? define
ADDITIONAL POSSIBLE PHASES FOR SUBSTANCE 1
When the substance is
DEFINEd, the database is searched up to the point in the database where
the entry is expected to be. During this process, if substances of the
same phase, but different form, are found, they are displayed on the
screen for information only. Data for these substances are not loaded
into memory. If the DEFINEd substance is found, data for it are loaded
into memory, but no confirmatory message is printed.
SUBSTANCE message can be used to find out which forms of a particular
substance in a given phase, are held on the database.
gentle introduction to using
the options available in THERMOTAB contains
examples, each directed towards achieving a particular outcome,
showing typical combination of commands which would be necessary
to achieve that end.
simple summary of
available can also be used as an index to obtain more detailed
help about each command.