NIST Chemistry WebBook

Frequently Asked Questions

• I can't find the chemical I am interested in. Why isn't it in your database?

  If you have only tried a name search, verify that the species is not in the database by conducting a chemical formula search. If that search fails, the species is not in the database.

  If you cannot find the species in the database, it means that we have no data for it. The database only includes chemical species for which we have data.

• Your database does not have the information I need. Are there other places I should look?

  There are many chemistry related sites on the internet. It is possible that one or more sites contain the data you need or provide an appropriate reference to the data in the literature. Chemistry related sites may be found through the use of search engines or an index of chemistry related sites.

  The most comprehensive and reliable source of chemical and physical property data is the chemistry literature. In many cases a literature search may be the best option for finding this type of data.

• What types of chemical species do you have in your database?

  The database currently consists mostly of organic compounds along with a few small inorganic compounds. Species are only included in the database if we have data for them.

• Can you help me with my homework?

  No.

• What atomic weight values are used in the data?

  The atomic weights used in the data are those used by the original authors. The molecular weights displayed are computed using weight data compiled by the NIST Physics Laboratory.

• Why can't I print a mass, IR, or UV/Vis spectrum?

  Many browsers will not print data that are displayed by an applet. There are three possible solutions to this problem:

  1. Click on the “image of digitized spectrum” link below the spectrum. This will display a larger static image of the spectrum that most browsers can display.
  2. Disable Java on your browser and re-load the page. On many browsers this will display an image of the spectrum that can be printed. Unfortunately this work-around will not work on all browsers.
  3. If the spectrum is available in SVG format, click on the “spectrum image in SVG format” link to view the spectrum in SVG format, and then print the spectrum. This option only works on browsers which support SVG.

• What is the proper citation for this web site?

  Please see our Citation Guide for information on how to cite data from this site.

• This site said “June 2005” release for a long time and now it has a date under the changes section of the main page. What is going on?

  Starting in 2006 we started making changes to the site incrementally rather than many changes at once. Originally we planned do a combination of large an incremental updates, but the incremental approach has worked well and we will continune to follow this approach in the future. The “June 2005” date was removed becuase is was becoming increasingly misleading.

• Can I make a link to your web page?

  Please feel free to make a link to our site as long as you do not in any way imply that our pages are part of your site. Please do not attempt to enclose our site in a frame. When linking to our site, we recommend that you link to our main page ( https://webbook.nist.gov/chemistry/).

  To link to an individual species, visit the page labeled as “Permanent link” and bookmark that page. Alternatively one can create links based on the following procedure:

  1. Obtain a IUPAC Standard InChI string for the species.
  2. Encode the InChI string so that it can be added to a URL. This consists of replacing the following characters with their URL safe codes:

     Character	Replacement code
     (	%28
     )	%29
     *	%2A
     +	%2B
     ,	%2C
     ;	%3B
     =	%3D
     ?	%3F

     Please note the forward slash (/) character should not be encoded.
  3. Append the resulting string to https://webbook.nist.gov/cgi/inchi/ to produce the URL for the link.

  The location of other pages in the site may change with future updates to our site.

• What happened to the vapor phase data in the fluid properties display applet?

  For saturated fluids, the fluid properties display applet will display properties for both the liquid and vapor phases. Properties for the liquid phase are denoted by a (l) after their name. Properties for the vapor phase are denoted by a (v) after their name. On some browsers the selectors for the X and Y axes of the plot will only display a limited number of items at a time. If this is the case, you may have to scroll the pop-up list from the selector to find the vapor phase properties which are at the bottom of the list.

• What is a Washburn correction?

  The Washburn correction consists of reduction or correction of the results of a calorimetric process to standard states. Correction is made for the following:

  • Compression of the condensed phase and gas phase species to 1 atm pressure
  • Enthalpy of solution and of dilution of the product gases in the aqueous phase (e.g. HCl, 1:600)
  • Vaporization of water because of the heat liberated by the reaction
  • Any energy changes associated with non-isothermal reactions

  More details on these corrections can be found on pages 72-74 of Cox, J.D.; Pilcher, G., Thermochemistry of Organic and Organometallic Compounds, Academic Press, New York, 1970.

• Can I get these data in a form I can use on my PC?

  The NIST Standard Reference Data program publishes a wide variety of electronic databases. Although NIST does not currently provide a product which contains all of the data in this site, significant portions of the data in this site and much more are available through NIST database products.

  For more information on NIST Standard Reference Data products, please see the NIST Data home page.

• How can I learn about NIST Standard Reference Materials?

  Visit the Standard Reference Materials^® Program home page or send e-mail to srminfo@nist.gov.