Its the end of the line for version 4.x - The new shiny v5 of CoolProp is at https://github.com/CoolProp/CoolProp . Perhaps one or two small bugfixes will be considered. v5 will mirror almost all the same functionality, and is mostly backwards compatible. Most users will notice no difference. We hope that you will all make the transition soon and help us to make CoolProp the most powerful thermophysical property library out there. Bye, go to https://github.com/CoolProp/CoolProp