I examined our copy of the standard and it seems that AGA 8 doesn\'t include the formulations for isothermal compressibility, I will consider the libraries mentioned by paolopemi, thanks for the help.
I am not sure it is the correct forum for this question but I haven't found similar threads...
For a Microsoft NET (VBA) application I need the isothermal compressibility (of natural gas) according AGA 8 (DC92), suggestions and comments (about source code or libraries available) are...