Highest Accuracy

Several basis schemes are used for very-high-accuracy calculations. The highest-accuracy HF calculations use numerical basis sets, usually a cubic spline method. For high-accuracy correlated calculations with an optimal amount of computing effort, correlation-consistent basis sets have mostly replaced ANO... 

For the accurate, a priori calculation of reaction rates, variational transition state calculations are now the method of choice. These calculations are capable of giving the highest-accuracy results, but can be technically dilficult to perform... 

There is no one best method for describing solvent effects. The choice of method is dependent on the size of the molecule, type of solvent effects being examined, and required accuracy of results. Many of the continuum solvation methods predict solvation energy more accurately for neutral molecules than for ions. The following is a list of preferred methods, with those resulting in the highest accuracy and the least amount of computational effort appearing first ... 

The quantities and Q that appear in equation 48 are approximations for the complete partition function. For highest accuracy, above about 9000 K, the partition functions should be used. 

A. Benzoic acid (C6H5COOH R.M.M. = 122.12). Analytical grade material has a purity of at least 99.9 per cent. For work demanding the highest accuracy, the acid should be dried before use by careful fusion in a platinum crucible placed in an oven at about 130°C, and then powdered in an agate mortar. 

This method has the drawback that an excess of oxidising agent is always present at the end point. For work of the highest accuracy, the indicator blank may be determined and allowed for, or the error may be considerably reduced by performing the standardisation and determination under similar experimental conditions. 

From a practical point of view it is better to use the maximum volume of sample possible, assuming there is no mass overload. This will allow the detector to be operated at the lowest possible sensitivity and in doing so provide the greatest detector stability and, as a consequence, the highest accuracy. 

These problems are not as significant In the macroenvironment, where many standards can be used for both calibration and standardization, since photodegradation of the sample Is usually not significant, running around 5-10%. However, If measurements of the highest accuracy or of small differences are required, these uncertainties... 

Glacial acetic acid, pure or mixed with other solvents, is one of the most attractive solvents for the titration of amines. Commercial acetic acid containing not more than 1% of water (Karl Fischer titration check) can be used in normal practice for the highest accuracy, however, the water content must be lowered to about 0.01% by addition of acetic anhydride and standing for 24 h not more than the stoichiometric amount of acetic anhydride should be used in order to avoid possible reactions with active hydrogen-containing analyte components such as primary or secondary amines or alcohols. A similar procedure is followed in the preparation of perchloric acid titrant from the commercial... 

A binary mixture is to be separated by distillation into relatively pure products. Where in the distillation column is the vapor-liquid equilibrium data required at the highest accuracy ... 

The important waveform parameter fshift is optimized on the basis of high range and velocity accuracy. The highest accuracy occurs if the intersection point in the A-v-diagram results from two orthogonal lines. 

In general, although the results of microcalorimetric studies do not pretend to provide enthalpy values of the very highest accuracy presently attainable by macroscale combustion calorimetry, they do offer a basis for application on a wide scale and are sufficiently precise for most purposes. The conflicting claims of accuracy and usefulness are particularly acute in the area of transition metal organometallic chemistry this review will attempt to follow a middle way between them. 

The question remains whether the mass of the electron m (0.548 mmu) has really to been taken into account in accurate mass work as demanded by the lUPAC convention (Chap. 3.1.4). This issue was almost only of academic interest as long as mass spectrometry never yielded mass accuracies better than several mmu. Nowadays, extremely accurate FT-ICR instruments become more widespread in use, and thus, the answer depends on the intended application The electron mass has to be included in calculations if the result is expected to report the accurate mass of the ion with highest accuracy. Here, neglecting the electron mass would cause an systematic error of the size of m. This cannot be tolerated when mass measurement accuracies in the order of 1 mmu or better are to be achieved. 

Measurement at several specific wavelengths with narrow bandwidth to remove interferences and provide highest accuracy for the constituent measured. 

It is therefore important to acquire data of the highest accuracy if unequivocal molecular compositions are to be determined. As a general rule, any molecular formulae for which the error (i.e. the difference between measured and theoretical masses) is greater than 10 ppm should be discounted. 

Starting with the pioneering work [52] Doppler-free two-photon laser spectroscopy was also applied for measurements of the gross structure interval in mnoninm. Experimental results [52, 53, 54, 55] are collected in Table 12.5, where the error in the first brackets is due to statistics and the second error is due to systematic effects. The highest accuracy was achieved in the latest experiment [55]... 

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