This is a new tool, available now at
http://www.minerazzi.com/tools/acid-base-systems/calculator.php
The tool replaces a previous one (removed from the web) where only simple acid-base solutions were considered.
The current one is not limited to the analysis of one solution or to acid-base titrations. Actually the tool also supports pH calculations of systems not undergoing titrations.
This is a great tool for real world applications like pH calculations from natural acid-base systems where a sample might consist of multiple acids mixed with several bases and/or their salts.
Examples of such systems are bio-samples (blood, saliva…) as well as geo-samples (sea and river water) and urban samples (sewage, wastewater,..).
This new tool is based on a general equation for acid-base systems that is solved using a residual analysis algorithm, avoiding the need for using inversion techniques, successive approximations, Newton-Raphson method, or the evaluation of derivatives or high-degree polynomials.