BufferCalc is an application designed to perform general buffer and pH calculations. BufferCalc, version 1 9/15/2002

Documentation The list of buffers may be sorted by name of the acid form, the name of the base form, the number of acidic hydrogens, the pKa, or the pKb. Use the pageup and pagedown keys on the PDA to move up and down the list.

Selecting a buffer from the list displays the different acid and base forms and their pKa values as a pH tree. The pKa button toggles to pKb and displays the pKb values. Use the arrow keys at the top of the form or the pageup and pagedown keys to step through the list. From this form there are three options, solution, titration, and alpha-diagram. The solution form is used to calculate the pH of a either the acid or base form of the buffer in solution from a user input concentration. The relative concentration of each of the acid and base forms of the compound are displayed. Additionally, the concentration distribution of the various forms of the buffer may be calculated from a pH and total concentration by tapping the equal sign button near the fraction/molarity button.

An alpha diagram displays in graphic form the fractional composition of the different acid and base forms of the compound as a function of solution pH. Tapping in the graph portion of the display moves the cursor to the indicated pH. Returning to solution the new pH and fractional composition is displayed. Note that the resolution of the screen imposes some restrictions on the pH values accessible from the screen.

The preferences form selected from the menu is used to select the number of digits to be displayed for pH values, concentrations and volumes. Also, the value of the Kw used in all calculations may be entered. All calculations are base on total mass and charge balance, incorporate all of the Ka values for a compound, and include the Kw.

The demonstration version has some limitations. Only 11 compounds are available in the database.

Author : DR Jeff Rosenthal

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