# Frequently asked questions

**Q:**What is Azeotrope.info for?

**A:**Azeotrope.info is a free application providing azeotropic data, based on vapor-liquid equilibrium calculations. So the program provides predicted (calculated) data instead of stored experimental data.

**Q:**Is this program free of charge?

**A:**Yes, the use of Azeotrope.info is completely free of charge.

**Q:**What sort of calculations are used? How does it work?

**A:**Find a brief overview of the model calculations on the page Method of calculation.

**Q:**What about the reliability of the calculation results?

**A:**They are generally precise. The non-ideality of the mixtures are modeled by UNIFAC (modified, Dortmund version), which is a widely used activity coefficient model. The literature is abundant with articles discussing the accuracy and reliability, usefulnes of the model. So this program is generally useful for informational, educational/demonstrational use. But when applying very special materials some caution is recommended.

**Q:**Found an error/mistake.

**A:**However during developing the program the point was to achive maximum reliability, errors can still occur, either due the inaccuracy of UNIFAC either due the imperfectness of the search algorithm. Sorry for any false or strongly inaccurate result, but the author of this app can not take any responsibility for any damages or losses originating from such calculation results. Use the program at your own risk!

**Q:**How can I download the program?

**A:**Sorry, no downloadable version here. This is only an on-line application.