Daniel - 

As a starting point, you might try Des Marais (1978, Analytical Chemistry,
v. 50, no. 9, pp. 1405-1406). Also, some textbooks on vacuum techniques
have data on vapor pressures for some gases which are not found in the CRC
Handbook of Chemistry and Physics - both of these latter sources have been
helpful to me in figuring this stuff out.

Good luck, 

Nat


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                                NAT LIFTON
Geosciences Department				      PHONE: (520) 626-8053
University of Arizona				      FAX:   (520) 621-2672
Tucson, Arizona  85721  USA	  	     E-MAIL: [log in to unmask]

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