Why Modify a Database?

We have already mentioned that although most modeling programs come with an associated database, the responsibility for using appropriate data is always that of the user, not the programmer or agency which supplies the database. There are basically two situations which might call for the user to change or add to the data supplied with the program.

• One is, of course, if the data become obsolete; i.e., new or better data become available, superseding those already in the database. Because most users are not solution chemistry experts, and/or have no time to keep up with the latest developments in solution and surface chemistry, this may not be a common situation.

• It is not uncommon, however, to find that the database simply has no data for some element that becomes important to us. We must then obviously find some data, and add them to the database. The easiest way to do this is simply to take data from the database of some other modeling program that happens to be more complete with respect to the missing element or elements. Alternatively, we can consult the primary literature.

In either case, it becomes important to understand the structure of the databases involved, because the modeling program expects to find the data in a certain format. To understand and conform to this format, we must read the program documentation, and in doing this it helps to understand the fundamentals of thermodynamics as given in Chapter 3.