The 7.0.510.13 version of pH Scale is available as a free download on our website. The actual developer of the free software is University of Colorado, Department of Physics. The most popular versions among the program users are 7.0, 6.0 and 1.0. PH Scale lies within Education Tools, more precisely Science Tools.
From the developer:
Test the pH of things like coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Visualize the relative number of hydroxide ions and hydronium ions in solution. Switch between logarithmic and linear scales. Investigate whether changing the volume or diluting with water affects the pH. Or you can design your own liquid!
You may want to check out more software, such as ISE/pH Ion Analyser, Chord Scale Generator or Scale & Chord Generator, which might be similar to pH Scale.