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H

2 303

.

R

BP

(2) 

Vap

where 

R = molar gas constant 

BP = boiling point 

 = result of equation (1)

4.21 Vapor Pressure 

This module calculates vapor pressure values. 

Prior to calculation you should select units for pressure and temperature, and specify 

temperature at which the vapor pressure value is to be calculated. 

The resultant dialog box contains structure, vapor pressure value, and temperature at which it 

was calculated.  All of this data can be printed at once by clicking Print or you may wish to edit 

the default report page in ChemSketch and then print it (click Insert to start editing). 

4.21.1 Limitations 

Restrictions are: 

A maximum of 255 atoms excluding hydrogen can be calculated; and 

Only C, H, O, S, P, N, F, Cl, Br, I, Se, Si, Ge, Pb, Sn, As, and B are permitted elements. 

4.21.2  How is it Calculated? 

The following equations are used to calculate vapor pressure at different temperatures: 

BP

t

760

log

VP

.

2

808

   (3) 

.

2731

t

.

015

BP

t

760

where t = temperature (in  C); BP

760

 = boiling point at 760 mm Hg (normal boiling point); 

 = 

result of equation (1) 

VP

VP

10

log

(4) 

4.22 Aqueous Solubility 

This module calculates accurate aqueous solubility values at any pH under the standard 

conditions ( and zero ionic strength).  The accuracy of calculations for simple structures is usually 

better than 0.2 0.5 logarithmic units (for complex structures it is better than 0.5 1.0 logarithmic 

units). 

The aqueous solubility of a chemical may be defined as the maximum amount of the chemical 

that will dissolve in pure water at a specified temperature.  Above this concentration, two phases 

will exist if the organic chemical is a solid or a liquid at the system temperature: a saturated 

aqueous solution and a solid or liquid organic phase. 

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User's Guide 

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