Download JESS Primer - Joint Expert Speciation System

The Thermodynamic Database 6
BROWSING THROUGH THE DATABASE
You can browse through the database using a conventional method of specifying reaction numbers
without typing them out in full. By entering certain special symbols, the program can be made to
display reactions on either side of the one last shown or to display the reaction last entered into the
database. The symbols are as follows:
Symbol
<
>
*
Meaning
Reaction number one less than that just shown
Reaction number one more than that just shown
The last reaction
Using this mechanism, you can easily and rapidly scan through a sequential series of reactions,
using just one keystroke to display each one. Type V, for View, at the JTH Command prompt and
then select, D, for Data. Enter any reaction number from 1 to * where * is the total number of
reactions in the database. Thereafter you can simply enter either > to display the next reaction
(and its data) or < to display the previous reaction.
Note that some reactions have more data than can be displayed on the screen at once. The program
will suspend output and display the prompt 'Continue? <Y> : '. You can have more of the data
shown ( e.g. by pressing |ENTER| ) or you can stop it by typing either N or Q.
BACKGROUND INFORMATION
Chemical species
The concept of a chemical species is fundamental to JTH. It uses information about species to
categorize all the thermodynamic data stored by it (so you can easily locate things) and to check
your input.
Every species in the JTH database is represented by a symbol. For example, the ion of Zinc(II) has
the symbol Zn+2 (in which, conventionally, the element's chemical abbreviation is followed by the
ion's signed electronic charge). When entering JTH symbols you can, in general, truncate them.
The programs will request clarification if this creates an ambiguity.
Symbols like Zn+2 are called ‘primitive’ to indicate that they are a basic building-block of the
database. For convenience, it is also possible to describe species in terms of combinations of
primitive symbols. In such cases, the symbol is referred to as a ‘composite’. In constructing a
composite symbol, you simply append the appropriate primitive symbols together, separating them
from one another with underscore characters, _.