The Lydersen method is a group contribution method for the estimation of critical properties temperature ( T_c), pressure ( P_c) and volume (V_c). The Lydersen method is the prototype for and ancestor of many new models like Joback, Klincewicz, Ambrose, Gani-Constantinou and others. The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature.

Equations

Critical temperature

T_c=\frac

Guldberg has found that a rough estimate of the

normal boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...

''T''_b, when expressed in

kelvins The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phy ...

(i.e., as an

absolute temperature Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics. Historically, thermodynamic temperature was defined by Kelvin in terms of a macroscopic relation between thermodynamic w ...

), is approximately two-thirds of the critical temperature ''T''_c. Lydersen uses this basic idea but calculates more accurate values.

Critical pressure

P_c=\frac

Critical volume

V_c\,=\,40+\sum G_i

M is the

molar mass In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, ...

and G_i are the group contributions (different for all three properties) for

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...

s of a

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

Group contributions

Example calculation

Acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

is fragmented in two different groups, one carbonyl group and two methyl groups. For the critical volume the following calculation results: V_c = 40 + 60.0 + 2 * 55.0 = 210 cm³ In the literature (such as in the Dortmund Data Bank) the values 215.90 cm³, 230.5 cm³ and 209.0 cm³ {{cite journal , last1=Kobe , first1=Kenneth A. , last2=Crawford , first2=Horace R. , last3=Stephenson , first3=Robert W. , title=Industrial Design Data—Critical Properties and Vapor Presesures of Some Ketones , journal=Industrial & Engineering Chemistry , publisher=American Chemical Society (ACS) , volume=47 , issue=9 , year=1955 , issn=0019-7866 , doi=10.1021/ie50549a025 , pages=1767–1772 are published.

References

Physical chemistry Thermodynamic models