Girolami method

The Girolami method is a method for the estimation of densities of pure liquids at room temperature. The focus of this model is the simple estimate of the material density and not its high accuracy.

Method

The method uses purely additive volume contributions for individual atoms and an additional correction factor for substances with specific functional groups that cause a volume contraction and therefore a higher density. Thus, the method is a mixture of an atom and a group contribution method.

Atom contributions

The method uses the following contributions for the different atoms:

A scaled molecular volume is now

And density then

Determined by the molar mass M. 5, the factor used to obtain the density in g · cm -3.

Group contributions

For some substances, provides Girolami found that their volume is calculated and their low density greater than that of the given formula. For components with

• A hydroxyl (alcohol )
• A carboxyl ( carboxylic acids)
• A primary or secondary amino functionality (amines )
• An amide group (including substituted on the nitrogen amides )
• A sulfoxide ( sulfoxides )
• A sulfone ( Sulfone )
• A ring ( non- fused )

It is sufficient for each occurrence is, to increase the density, which is determined from the primary conditional equation by 10%. Sulfone for this factor is to be applied twice ( 20%).

Another special case of substances having a fused ring systems such as naphthalene. The density of these substances is a 7.5% increase per ring for naphthalene thus by 15%.

If several of these corrections are necessary, they are to be added, but not total 130% also.

Example calculations

The author gives a mean square error (RMS) of 0.049 g · cm -3 for 166 tested components. Only two components ( acetonitrile and dibromochloromethane ) an error was greater than 0.1 g · cm -3 determined.