Download of Sigfit 1.2 for Mac was available from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This application is developed for Mac OS X 10.6.6 or later.
The following versions: 1.2 and 1.1 are the most frequently downloaded ones by the program users. This software for Mac OS X is a product of J.P.G. Malthouse. We recommend checking the downloaded files with any free antivirus. The program lies within Education Tools, more precisely Science.
From the developer:
This program fits data to the equations:-
kobs = k/(1+[H]/Ka)
kobs = k/(1+Ka/[H]
When "Fit" is selected a linear reciprocal plot is used to make the initial estimates of kobs and the pKa. These values of kobs and pKa are then used as the initial estimates to fit the experimental data using an iterative, non linear least-squares regression program.
You may want to check out more software for Mac, such as Datawrite, which might be similar to Sigfit.