The Girolami method,[1] named after Gregory Girolami, is a predictive method for estimating densities of pure liquid components at room temperature. The objective of this method is the simple prediction of the density and not high precision.
The method uses purely additive volume contributions for single atoms and additional correction factors for components with special functional groups which cause a volume contraction and therefore a higher density. The Girolami method can be described as a mixture of an atom and group contribution method.
Atom contributionsedit
The method uses the following contributions for the different atoms:
it is sufficient to add 10% to the density obtained by the main equation. For sulfone groups it is necessary to use this factor twice (20%).
Another specific case are condensed ring systems like Naphthalene. The density has to increased by 7.5% for every ring; for Naphthalene the resulting factor would be 15%.
If multiple corrections are needed their factors have to be added but not over 130% in total.
The author has given a mean quadratic error (RMS) of 0.049 g·cm−3 for 166 checked components. Only for two components (acetonitrile and dibromochloromethane) has an error greater than 0.1 g·cm −3 been found.
Referencesedit
^Girolami, Gregory S. (1994). "A Simple "Back of the Envelope" Method for Estimating the Densities and Molecular Volumes of Liquids and Solids". Journal of Chemical Education. 71 (11): 962–964. doi:10.1021/ed071p962.
External linksedit
Online calculator for the Girolami model
January 01, 1970
girolami, method, named, after, gregory, girolami, predictive, method, estimating, densities, pure, liquid, components, room, temperature, objective, this, method, simple, prediction, density, high, precision, contents, procedure, atom, contributions, group, c. The Girolami method 1 named after Gregory Girolami is a predictive method for estimating densities of pure liquid components at room temperature The objective of this method is the simple prediction of the density and not high precision Contents 1 Procedure 1 1 Atom contributions 1 2 Group contribution 2 Example calculation 3 Quality 4 References 5 External linksProcedure editThe method uses purely additive volume contributions for single atoms and additional correction factors for components with special functional groups which cause a volume contraction and therefore a higher density The Girolami method can be described as a mixture of an atom and group contribution method Atom contributions edit The method uses the following contributions for the different atoms Element Relative volume Vi Hydrogen 1 Lithium to Fluorine 2 Sodium to Chlorine 4 Potassium to Bromine 5 Rubidium to Iodine 7 5 Cesium to Bismuth 9 A scaled molecular volume is calculated by V S i V i displaystyle V S sum i V i nbsp and the density is derived by d M 5 V S displaystyle d frac M 5 cdot V S nbsp with the molecular weight M The scaling factor 5 is used to obtain the density in g cm 3 Group contribution edit For some components Girolami found smaller volumes and higher densities than calculated solely by the atom contributions For components with a hydroxylic function Alcohols a carboxylic function Carboxylic acids a primary or secondary amine function an amide group incl amides substituted at the nitrogen a sulfoxide group a sulfone group a ring non condensed it is sufficient to add 10 to the density obtained by the main equation For sulfone groups it is necessary to use this factor twice 20 Another specific case are condensed ring systems like Naphthalene The density has to increased by 7 5 for every ring for Naphthalene the resulting factor would be 15 If multiple corrections are needed their factors have to be added but not over 130 in total Example calculation editComponent M g mol Volume VS Corrections Calculated density g cm 3 Exp density g cm 3 Cyclohexanol 100 6 2 13 1 1 2 26 One ring and a hydroxylic group 120 d 1 2 100 5 26 0 92 0 962 Dimethylethylphosphine 90 4 2 11 1 1 4 23 No corrections d 90 5 23 0 78 0 76 Ethylenediamine 60 2 2 8 1 2 2 16 Two primary amine groups 120 d 1 2 60 5 16 0 90 0 899 Sulfolane 120 4 2 8 1 2 2 1 4 24 One ring and two S O bonds 130 d 1 3 120 5 24 1 30 1 262 1 Bromonaphthalene 207 10 2 7 1 1 5 32 Two condensed rings 115 d 1 15 207 5 32 1 49 1 483Quality editThe author has given a mean quadratic error RMS of 0 049 g cm 3 for 166 checked components Only for two components acetonitrile and dibromochloromethane has an error greater than 0 1 g cm 3 been found References edit Girolami Gregory S 1994 A Simple Back of the Envelope Method for Estimating the Densities and Molecular Volumes of Liquids and Solids Journal of Chemical Education 71 11 962 964 doi 10 1021 ed071p962 External links editOnline calculator for the Girolami model Retrieved from https en wikipedia org w index php title Girolami method amp oldid 1135993701, wikipedia, wiki, book, books, library,
