Is there a free website that provides the latent heat of vaporization
at various temperatures for ethylene glycol?

You can try the latent heat of vaporization applet on the
thermochemical properties estimator page
<http://www.pirika.com/chem/TCPEE/TCPE.htm> to estimate this as a
function of temperature.  The estimate should be good to +/- a KJ/mol
or two.

There are some values on-line, but you will encounter three problems:

Problem 1 (the biggest one): Different sites list different values.

Problem 2: In most cases, the values are for two temperatures only.

Problem 3: If there is a mixture, the heat of vaporization _might_
vary from the values for ethylene glycol alone. (This won?t matter if
you aren?t interested in mixtures such as water/antifreeze.) One site
gives heats of vaporization for a series of temperatures, but if you
look at the title of the article cited, it appears that these are for
ethylene glycol dissolved in an imide.


The values from various sites are given below:


1) The NIST values are:

273 K      61.9 +- 6.3 kJ/mol (Original 1937 (?) value had been 57.07 kJ/mol)
409 K      68.  +- 2.

http://webbook.nist.gov/cgi/cbook.cgi?ID=C107211&Units=SI&Mask=4#Thermo-Phase

2) Another site uses the same data sources and gives the values as:

273 K            61.92 +- 6.28
409 - 469 K   67.8 +- 1.7

http://www.fibronet.com.tw/member/chemical/cas/107-21-1.htm

3) At the National Toxicology Program site, the value is given as:

50.5 kJ/mol (no temperature given)

http://ntp.niehs.nih.gov/index.cfm?objectid=E87BF66D-BDB5-82F8-FD28184E0A518718

They list the data source as 
?Source: the National Library of Medicine's Hazardous Substance
Database, 03/28/2005.?

http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~jJkSfe:1

which, in turn, gives their data source as 

?Lide, DR (ed.). CRC Handbook of Chemistry and Physics. 81st Edition.
CRC Press LLC, Boca Raton: FL 2000, p. 6-110?


4) In a 1990 IUPAC article, "RECOMMENDED METHODS FOR THE PURIFICATION
OF SOLVENTS AND TESTS FOR IMPURITIES 1,2=ETHANEDIOL AND
2,2,2-TRIFLUOROETHANOL"

the enthalpy of vaporization is listed as

52.69 kJ/mol      298 K
50.46 kJ/mol   at normal boiling temperature

http://www.iupac.org/publications/pac/1990/pdf/6201x0139.pdf

The article cites a reference for each of these values.

5) Another site is a "thermochemical properties database."

http://www.fiz-chemie.de/infotherm/html/mol_pages/1/1/mol5543.html

It gives values for enthalpy of vaporization of ethylene glycol, but
the values may be for ethylene glycol dissolved in an imide. The
enthalpy of vaporization was determined for a range of temperatures
from 303 K to 336 K and at 298.15 K

298.15 K  65.40 kJ/mol
303.2 K   65.16 kJ/mol
336.2 K   63.52 kJ/mol

http://www.fiz-chemie.de/infotherm//servlet/infothermSearch

Have fun comparing the above to what you get from the pirika site.

Search strategy: 
?ethylene glycol? ?heat of vaporization?
?ethylene glycol? ?enthalpy of vaporization?

I just tried the pirika site. I get 56 kJ/mol at 298 K - in between
the highest and lowest experimental values.