Importing titration data

Titration data needs to be in the format described in Variables and conventions in order to work with Calkulate functions. The io module contains a function to import text files generated by the widespread VINDTA instrument in a suitable format, or to load titration datasets that were simulated and reported by D81.


Import VINDTA-style .dat files

The io.datfile function is useful if titration data is in a text file (e.g. the format typically generated by a VINDTA instrument). This format is easy to replicate with any other sort of data that you may have.

Syntax:

volAcid, emf, tempK = calk.io.datfile(datFile, delimiter='\t', skip_header=2,
    **kwargs)

The input datFile is a string containing the .dat file's name (and path). The other optional inputs, including **kwargs, get passed to NumPy's genfromtxt function to assist in opening the file correctly.

What format is that?

A text file with the extension '.dat' for each titration that looks something like this (with extra rows in place of the ...):

bottle  CRM-144-0435-4  0   0   0   0   0.00    0.00    35.000  4.000   0.00    0.0
24.857  35.000  0.000   0.000
0.000   187.600 24.857
0.150   209.350 24.855
0.300   236.800 24.857
...     ...     ...
3.750   483.800 24.862
3.900   486.350 24.865
4.050   488.650 24.862

The first two lines contain various bits of user-inputted information about the sample. Other than skipping past them to the titration data, these lines are totally ignored by Calkulate.

The rest of the file has a row for each acid addition step in the titration. The space- or tab-separated columns are:

  1. Volume of acid added in ml;
  2. Measured EMF of the sample + acid mixture in mV;
  3. Temperature of the sample + acid mixture in °C.

Creating .dat files

If you have imported or simulated titration data in the format expected by Calkulate, you can export it in this .dat file format using the io.writeDat function:

calk.io.writeDat(datFile, volAcid, emf, tempK, line0='', line1='')

Be careful - if the specified datFile already exists then it will be overwritten without warning!

The optional line0 and line1 inputs allow you to add anything to the first two lines of the .dat file; these lines are ignored by the Calkulate import function.


Simulated titrations

Titration data simulated by D81 and reported in his Tables 1 (without phosphate) and 4 (with phosphate) are available within Calkulate. They can be imported as follows:

(massAcid, pH, tempK, massSample, concAcid, pSal, alk, concTotals,
      eqConstants) = calk.io.Dickson1981(withPhosphate=True)

The input withPhosphate is a logical determining whether titration data should include phosphate (default behaviour, True, D81 Table 4) or not (False, D81 Table 1).