Boiling point, estimation

This is not a very satisfactory fit even when the value of R = 0.9546, as the standard error of boiling point estimation is 32.4 °C. The maximum error in estimation is with methane, where the error is 85.3 °C. The curve of experimental T, versus Nc has a negative second derivative and makes a downward arch, and is not well represented by a straight line, especially at the two ends and at the middle. 

Many of the published estimation methods have been derived for specific homologous series, i.e., particular chemical classes such as n-paraffins, alcohols, substituted benzenes, etc. Table 2.1 provides a list of references for such methods. Within such a class, boiling point estimation can be fairly accurate (e.g., having average absolute errors under 10°C) ... 

Availability of Boiling Point Estimation Methods for Specific Chemical Classes.1... 

Overview of Boiling Point Estimation Methods Described in this Chapter... 

Table 2.4 provides examples of the molecular descriptors Equation (3) requires and the resulting boiling point estimates. 

Lai et al. (1987) have developed what is likely the most accurate boiling point estimation method using a nonlinear group contribution method. The method is applicable to com-... 

Method Errors in Boiling Point Estimates Using Lai et al. s Method.3... 

The compilations of CRC (1-2), Daubert and Danner (3), Lange s Handbook (8-9), web sites (18-20), and Yaws (21-35) were used extensively for enthalpy of vaporization. The Kistiakowsky rule (13) and Riedel method (13) were primarily used for estimates of enthalpy of vaporization at the boiling point. Estimates for critical temperature were primarily based on the Gates-Thodos metod (10) and Grosse equation (10). 

Promethium is a silver-white metal with a melting point of 2,120°F (1,160°C) and a boiling point estimated at about 5,400°F (3,000°C). Its density is 7.2 grams per cubic centimeter. The physical properties of promethium are of less interest to scientists than its radioactive properties. 

Only limited information is available about actinium. It is known to be a silver metal with a melting point of 1,920°F (1,050°G) and a boiling point estimated to be about 5,800°F (3,200°C). The element has properties similar to those of lanthanum. Generally speaking, elements in the same column in the periodic table have similar properties. Few compounds of actinium have been produced. Neither the element nor its compounds have any important uses. 

Pc = critical pressure estimated from group contributions Ti,r = reduced normal boiling point estimated from Eq. (2-9) Xp = log(l atm/P eas)... 

Although estimation methods for the acentric factor are available (e.g., group contribution method of Constantinou and Gani [11]), this concept is not recommended, as an estimation of co would only be a redundancy of the normal boiling point estimation. To avoid inconsistencies, it is recommended that co is always calculated by its defining equation 2.157. If the vapor pressure curve is unknown, the normal boiling point and the critical point can be estimated, and the Hoffmann-Florin equation or the Rarey/Moller method (Section 3.2.1) can be used to calculate the vapor pressure curve. 

There is an opportunity of taking a known substance with a similar structure as reference. Because of the high uncertainty, for the normal boiling point estimation this procedure is recommended to avoid possible large errors. 

An additional role in my professional life is a Honorar) Professor position in Durban, South Africa. Currently, my group there consists of 4 MSc students, all highly motivated. We developed and published estimation methods for a number of important properties like vapor pressure, liquid viscosity, water and alkane solubility, etc. The first of our methods on normal boiling point estimation is already generally regarded as the primary and best method available. 

The one-fluid approach can be used with some of the models presented earlier. In the method of Mehrotra [II], the one-fluid model can be used to obtain the needed normal boiling temperature, T, from = [ZxjT y ], if the mixture is well defined. This proposal has not been tested in that method. However, Orbey and Sandler [ 13] found this boiling-point estimation method to be suitable for use in their viscosity model as discussed later. 

Note that the distillate dew-point and bottoms boiling-point estimation is partially trial and error, since the distribution of the other components in the distillate and bottoms is not known and can affect these values. 

Using the enthalpy of vaporization of water at the normal boiling point, estimate its values from 0°C to the critical and comment on their accuracy. 

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