Titrafit

The algorithm which the fit function is based on is inspired by:
Binnewies, M.: Chemische Gleichgewichte. VCH, Weinheim, 1996.

Prerequisites

The following Python 3 packages must be installed to use Titrafit:

• Matplotlib
• NumPy
• PySide2
• SciPy

Input data format

The for the input data must be in an xy format with a dot as decimal separator. The first column contains the volume of the added NaOH solution in ml and the second column the corresponding pH values. Lines starting with # are ignored.

Example files are provided in the exampledata directory. For these files, V0 = 200 ml and c(NaOH) = 0.1 mol/l. The pKa values of sulfuric acid are -3 and 1.8, those of phosphoric acid are 2.12, 7.20 and 12.36.

Building tfast

Titrafit provides a C++ implementation of the fit function which greatly deduces the time required for the computation. For the compilation of the corresponding module, the following software is required:

• Pybind11 headers (available via pip and some Linux package managers)
• Python 3 headers (usually bundled with Python 3, in separate package libpython3-dev on Debian/Ubuntu)
• A C++14-capable compiler such as g++, Clang oder MSVC

On Linux, tfast can be compiled with the following command:

g++ -std=c++14 -O2 -fPIC -shared -o tfast.so `python3 -m pybind11 --includes` tfast.cpp

On Windows, the compilation command is as follows:

cl /O2 /LD /I <C:\path\to\Python\>include tfast.cpp /link <C:\path\to\Python>\libs\python3<x>.lib /OUT:tfast.pyd

Editing the UI files

The user interface is defined in the .ui files which can be edited with Qt Designer. From these, the corresponding ui_*.py files are generated with pyside2-uic, e.g.:

pyside2-uic inputform.ui > ui_inputform.py

The resulting ui_*.py files are included in the Git repository so Titrafit can be run right after cloning the repository, without any additional build steps.