11/17/2003 tcaw-thermodynamics-1103.doc 1823 words
By Stephen R. Heller (Today’s
Chemist Not at Work)
11/17/2003 tcaw-thermodynamics-1103.doc 1823 words
By Stephen R. Hellersteve@hellers.com
passed Pchem , you probably
struggled with thermodynamics, and wondered if there was a better way. Well, today
there is a better way to obtain thermodynamic data; the Web. There are dozens
of sources of thermo data available on the web. The University of Illinois at Chicago (UIC) has an excellent web
page with links to over 100 Data & Property
Calculation Websites (3). This article
will cover just a few of the major sites, both free and paid, which are now
available. These include: the NIST
WebBook, DIPPR (4), Dechema (5), and FIZ-Berlin Infotherm (6)
According to NIST, usage of the web based WebBook (1) database and search system exceeds 20,000 users per week with over 600,000 different IP addresses per year accessing just the WebBook. While the WebBook covers a wide variety of subjects, its core is thermochemical and thermophysical data. The NIST WebBook is not the only source of thermodynamic data and there are a number of other thermodynamic databases, including the newest such system, the FIZ-Berlin Infortherm system (2).
What are people doing with this data? The need and value of thermodynamics data is quite varied and deep. In the chemical process industry it would be difficult to build an efficient and cost effective plant for a chemical without good, high quality thermophysical and thermochemical properties. In the field of petroleum and bulk chemicals, where profit margins are slim, good data can be the difference between a well run profitable operation or one that is in the red. This data is needed for scale up testing of large batches of chemicals. Thermodynamics data is used to design systems to minimize heat losses. Thermo data helps in the design of distillation columns. In these time, when everyone is very cost sensitive, good thermo data will both improve the quality of the production as well as improve the quality, leading to better profit margins.
NIST Chemistry WebBook
The NIST Chemistry WebBook is by far the most well used source of thermodynamics data. At present all the information the WebBook is free, which in addition to its high quality of evaluated data, is probably the major reason for its high and widespread usage. It contains data on over 48,000 chemicals including thermochemical data for over 7000 organic and small inorganic compounds such as
o Enthalpy of formation
o Enthalpy of combustion
o Heat capacity
o Phase transition enthalpies and temperatures
o Vapor pressure
and reaction thermochemistry data for over 8000 reactions on
o Enthalpy of reaction
o Free energy of reaction
The WebBook has numerous, easy to use, search capabilities including: chemical name, formula, molecular weight, CAS Registry number, author, structure, substructure, and reaction.
The DIPPR database consists of experimental data, estimated values where necessary, temperature-dependent correlation coefficients, references, notes, quality codes, and other information required for proper use of the DIPPR database in computer-accessible form together with software for searching, accessing, and using the data and accompanying information.
The database includes source data values and references, data quality codes, and background information, such as molecular structure, synonyms, hazard properties, miscellaneous properties, notes, and explanations. It now contains data for 29 fixed-value properties and 15 temperature-dependent properties. Data for approximately 1811 industrially important compounds are included. As far as possible, values for all these properties for each chemical are entered. If experimental data are not available, values are estimated when possible. Temperature-dependent correlation coefficients, applicable upper and lower temperature limits, and values computed at these limits are included for temperature-dependent properties. Fundamental SI units are used. Some of the DIPPR data is available at no cost. The data is very useful for modeling programs. The database is available online via the Chemical Abstracts Service STN computer network (7). The database is also available in a limited form at Brigham Young University. If you are a student or employee of an educational institution and would like access to the DIPPR 801 student database, please go to the BYU website listed in the references (8).
DECHEMA (Society for Chemical Engineering and Biotechnology) is a non-profit
making scientific and technical society based in Frankfurt/Main, Germany. It
was founded in 1926.
Nowadays it has over 5000 private and institutional
members. One of their main activities has been the creation and
dissemination of the Detherm database and search system.
The Detherm database provides thermophysical property data for about 21,000 pure compounds and 101,000 mixtures. These data are indispensable for the design of apparatus and chemical production facilities. .
Detherm contains Literature values, together with bibliographical information, descriptors and abstracts. At the time 4.2 million data sets are stored
The following properties are stored:
· phase equilibrium data
· vapor pressures, critical data
· thermodynamic properties
· transport properties
· surface tensions
· electrolyte data
Infotherm - FIZ Berlin
The last of the database and search systems to be described
here is the Infotherm system from FIZ-Berlin -the "Chemistry Information
Centre" (Fachinformationszentrum Chemie, FIZ Chemie Berlin. Launched late
in 2003 this database of the thermophysical properties of substances
"Infotherm" in XML. XML (Extended Mark-up Language) is the standard
for information services in the Internet and in Internet-based company networks
(Intranets). By making Infotherm available via the Web, FIZ Chemie Berlin hopes
to target those chemical engineering offices and companies who are increasingly
using the Internet to meet their information requirements. The integration of
the database in company Intranets is simple using XML technology.
The quality Infotherm database delivers data on pure compounds and on mixtures, such as PVT properties, phase equilibria, transport and surface properties, calorific properties, solid-liquid equilibria. The complete database currently contains more than 90,000 data records for mixtures and about 199,000 records for pure substances. The first release in late 2003 contained more than 80,000 data sets on mixtures and more than 60,000 on pure compounds. Each piece of data may be accessed via the chemical name, the trivial name, molecular formula, or via the CAS Registry Number. The data originates from journal articles, handbooks and data collections which are evaluated by FIZ Chemie Berlin and which cover the time-period from 1985 until the present. The database is being updated monthly. The database provides information on the thermophysical properties of 6,300 pure chemical compounds and 23,000 mixtures along with full bibliographic data. 150,000 tables contain PVT-properties, phase equilibria, transport and surface properties, caloric properties, and acoustic and optical properties. Searching the database and the "preview" display format of results is free of charge. This policy is somewhere between the NIST data which is available at no cost, and the Dechema data which is all for a fee. The DTherm does let you know when the information is available at no cost. Infotherm offers pay-per-view access or full access to all documents on a license basis. Pay-per-view users can purchase full access to an individual document from the free preview format. For considerable flexibility, all purchased documents can be downloaded in several data formats. Note: The CSV-download exports only the data in a spreadsheet format (for e.g.. MS-Excel). Optionally, all documents can be stored in the “my infotherm” section by selecting from the hit list. These documents will be available in future sessions. Besides licensing the entire database customers can also purchase pre-paid
can be transformed into an unlimited license if the usage exceeds the
respective license fee.
Data for the Antonine equation
An example of search in three of these systems and the
resulting output is shown
below. In all the examples the search was for Antoine Equation data for
While chemists often
use the Clausius-Clapeyron equation
to estimate the vapor pressures of pure liquids or solids and it works well for
most applications. Several of the assumptions made in the derivation of the
equation fail at high pressure and near the critical point, giving inaccurate
results. Chemical engineers often need more reliable vapor pressure estimates.
The Antoine equation is a simple 3-parameter fit to experimental vapor
pressures measured over a restricted temperature range:
log P = A -
where A, B, and C are "Antoine coefficients" that vary from substance to substance. Sublimations and vaporizations of the same substance have separate sets of Antoine coefficients, as do components in mixtures. The Antoine equation is accurate to a few percent for most volatile substances (with vapor pressures over 10 Torr).
Figure 1 – NIST WebBook Antoine Equation Data for Benzoic Acid
The example below is the result of a search for Antoine equation data on Benzoic Acid data. All data from the Dechema database is available for a fee, the amount of which is shown in each of the 5 hits in Figure 2.
Figure 2 – DTherm Antoine Equation Data for Benzoic acid
The search below in the Infotherm system starts out with the web page displaying the search options, including search by name, formula, CAS registry number, the type of data you want to search for (the pull down menus list dozens of properties, similar to that found in the Dechema search system), a bibliography search for author, title, and so on, the type of system (pure, binary, and then up to denary) and the box at the bottom displays the search results.
Figure 4 – Infotherm Antoine Equation Data summary output for Benzoic Acid
Figure 5 – Infotherm Antoine Equation Data complete output for Benzoic Acid
Figures 4 and 5 shows the hit resulting from the search and the detailed output. In this case, as the example chosen is one of those available at no cost, it is possible to show an entire Infotherm record.
In summary, thermodynamics data, a very important need for much industrial research, is now being made more widely available via the web. The examples shown here are just a few of the many sources of this information and again proving why the web is such a wonderful resource in making it easier for today’s chemist to do their work most quickly and efficiently.