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[cheesecake]

Hi anyone knows where i can get the antoine equation constants from the internet? is it possible to use antoine equation for temperatures around 300-340 celcius? or what equation should i use to obtain vapour pressures of certain components? my components are all gases. thanks!

[Art Montemayor]

Cheese:

For a student who is privileged to be studying in Great Britain, surrounded by traditional and bountiful sources of knowledge and information, you are not showing any resourcefulness or initiative. Your query is not only basic and elementary, it is easily resolved by going to any convenient library where you are located at – or simply surfing the Internet and downloading the information.

Some years ago (I think it has been over 10 years) a bright and resourceful chemical engineering student sat down and resolved his/her own needs. He/she went to a technical library and borrowed “The Properties of Gases and Liquids” (3rd Edition) by Reid, Prausnitz, and Sherwood; McGraw-Hill; New York. This book is a classic and the appendix listed 468 compounds and elements with all their related Physical Properties – including the Antoine Coefficients. This person simply sat down and typed in all the free information into a “flat-file" database: an Excel spreadsheet. Once done, this information was his/hers and it was soon distributed over the Internet. Chris Haslego offered this spreadsheet for free downloading for many years on this Website. I don’t know if it is still offered. I’ll leave that up to your resourcefulness. I have a copy.

The same book came out with a 4th edition in 1987 with 618 compounds – and increase of 32% over the previous version.

Additionally, Greg Reklaitis in his “Introduction to Material & Energy Balances” (John Wiley, 1983) gave a listing of Antoine Coefficients for 178 compounds. His source was the FLOWTRAN database developed by the Monsanto Company and prepared by Dr. D. R. Schneider. If this information is readily available on this side of the Atlantic, I feel certain that there must be many more sources in Great Britain’s great store of libraries – free to all who seek knowledge. The engineering universities probably have even more sources of such data also available.

I am sure that if you do some basic, simple research and spend some time surfing or scanning your library you will find much information on Antoine Coefficients. To answer your specific questions:

1. Yes, you can employ Antoine Coefficients to arrive at a compound’s vapor pressure. However, the Antoine equation has a bad reputation for having a narrow band of accuracy. If you don’t know the accuracy range for the coefficients that you use, you could develop some erroneous results. Some coefficient sources will qualify the accuracy range. Be careful.
2. You can use Antoine’s equation, the Harlacher equation, or simply try the NIST free database on the Internet. I have recommended this source for years on this Forum. I’ll let you search out the many threads where I have specified the exact URL

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Guido, one of the top expert contributors on this Forum has also previously furnished some very good, sound advice to all students regarding the Antoine relationship: Be careful and wary of the units employed with the constants given. Some people have no real knowledge that the constants are specific to a certain form of the Antoine equation and they get them all mixed up. The result is erroneous results.

With all this information, you should have your basic, simple problem resolved. All you have to do is let your feet or fingers do the walking.

Good Luck.