Experimental value adjusted

Experimental values adjusted to OK by subtracting 1.5kcal/mol following the procedure of Ref. 33. 

In practice, however, it is recommended to adjust the coefficient m, in order to obtain either the experimental vapor pressure curve or the normal boiling point. The function f T ) proposed by Soave can be improved if accurate experimental values for vapor pressure are available or if it is desired that the Soave equation produce values estimated by another correlation. 

A method, proposed more recently by FULLER, SCHETTLER and GlDDlNGSf8 . is claimed to give an improved correlation. In this approach the values of the diffusion volume have been modified to give a better correspondence with experimental values, and have then been adjusted arbitrarily to make the coefficient in the equation equal to unity. The method does contain some anomalies, however, particularly in relation to the values of V for nitrogen, oxygen and air. Details of this method are given in Volume 6. 

In order to allow a better appreciation of this approach it wili be illustrated in the case of a saturated hydrocarbon whether it is linear, branched or cyclic. In order to get the best possible adjustment only the experimental values listed in Part Three, which were obviously in line with the expected result and rejected flashpoints oc , were used. 

The study is based on four iinear hydrocarbons (in Ci, Ce to Ca) and the model uses Antoine and Clapeyron s equations. The flashpoints used by the author do not take into account all experimental values that are currently available the correlation coefficients obtained during multiple linear regression adjustments between experimental and estimated values are very bad (0.90 to 0.98 see the huge errors obtained from a correlation study concerning flashpoints for which the present writer still has a coefficient of 0.9966). The modei can be used if differences between pure cmpounds are still low regarding boiling and flashpoints. 

A number of empirical methods exist for the adjustment of covalent bond lengths for ionic effects.34,35 These are based primarily on formulas that involve the sum of the covalent radii corrected by a factor that is dependent on the electronegativity difference between the atoms. In many instances, quite good agreement is obtained between the predicted and experimental values, as shown by the listing in Table I. 

The rkint function integrates the differential equation in f-ruteeq from cAo at t = 0 to cAi at t = ti. The value of cAi is then compared with the experimental value of cA values of kA and n are adjusted until the sum of squared residuals between the predicted and experimental concentrations is minimized. 

A very severe test of these virial-coefficient equations for the sea-water-related Na-K-Mg-Ca-Cl-S0,-H 0 system has been made by Harvie and Weare (37) who calculated tne solubility relationships for most of the solids which can arise from this complex system. There are 13 invariant points with four solids present in the system Na-K-Mg-Cl-SO - O and the predicted solution compositions in all 13 cases agree with the experimental values of Braitsch (38) substantially within the estimated error of measurement. In particular, Harvie and Weare found that fourth virial coefficients were not required even in the most concentrated solutions. They did make a few small adjustments in third virial coefficients which had not previously been measured accurately, but otherwise they used the previously published parameters. 

While this relationship is simple, it introduces more errors because the activity coefficient (or more normally, the mean ionic activity coefficient y ) is wholly unknown. While y can sometimes be calculated (e.g. via the Debye-Huckel relationships described in Section 3.4), such calculated values often differ quite significantly from experimental values, particularly when working at higher ionic strengths. In addition, ionic strength adjusters and TISABs are recommended in conjunction with calibration curves. 

In Fig. 5, the agreement of the calculated absolute intensity values with the corresponding experimental values is an indication of the high quality of the ab initio dipole moment surfaces employed in the calculation. The qualitatively correct appearance of the bands indicates that our solution of the rotation-vibration Schrodinger equation and the potential energy surface employed are satisfactory. It should be emphasized that the ab initio potential energy and dipole moment surfaces have not been adjusted to fit experiment. 

One can easily adjust the values of the dielectric constants D(, and Dj to obtain the experimental values of W, as in Table 4.4. With a choice of = 19.6 and Dj. = 51.0 for water, and D. = 12.5 and Dj. = 31.8 for 50% water-ethanol, we obtain the experimental values of W. We now compute the total correlation function for the two-state model for succinic acid. Here the correlation cannot be computed as an average correlation of the two configurations (see Section 4.5). The total correlation of the equilibrated two-state model is... 

Results of calculations carried out with three different selection schemes and an ST03G AO will be described. The reader will recall that the scale factors for this basis are traditionally adjusted to give molecular geometries, and this must be remembered when interpreting the results. By now the reader should suspect that such a basis will not produce very accurate energies. Nevertheless, we see that the qualitative trends of the quantities match the experimental values. 

The calculated barrier for the cyclization of 33t to 29 is 6 kcal/mol after taking into consideration that the CASPT2 method overestimates the energy difference between open- and closed-shell states by 3 kcaFmol. The correspondingly adjusted predicted 6 kcal/mol barrier is in nearly exact agreement with the experimental value (5.6 0.3 kcal/mol). " ... 

---