Erroneous value

An apparent systematic error may be due to an erroneous value of one or both of the pure-component vapor pressures as discussed by several authors (Van Ness et al., 1973 Fabries and Renon, 1975 Abbott and Van Ness, 1977). In some cases, highly inaccurate estimates of binary parameters may occur. Fabries and Renon recommend that when no pure-component vapor-pressure data are given, or if the given values appear to be of doubtful validity, then the unknown vapor pressure should be included as one of the adjustable parameters. If, after making these corrections, the residuals again display a nonrandom pattern, then it is likely that there is systematic error present in the measurements. ... 

The table convincingly demonstrates how the unsuspected presence of micropores can lead to an erroneous value of the specific surface calculated from a Type II isotherm by application of the standard BET procedure. According to the foregoing analysis, the external specific surface of the solid is 114m g" the micropore volume (from the vertical separation of isotherms A and E) is 105 mm g but since the average pore width is not precisely known, the area of the micropore walls cannot be calculated. Thus the BET figure of 360m g calculated from isotherm E represents merely an apparent and not a true surface area. 

It would be difficult to over-estimate the extent to which the BET method has contributed to the development of those branches of physical chemistry such as heterogeneous catalysis, adsorption or particle size estimation, which involve finely divided or porous solids in all of these fields the BET surface area is a household phrase. But it is perhaps the very breadth of its scope which has led to a somewhat uncritical application of the method as a kind of infallible yardstick, and to a lack of appreciation of the nature of its basic assumptions or of the circumstances under which it may, or may not, be expected to yield a reliable result. This is particularly true of those solids which contain very fine pores and give rise to Langmuir-type isotherms, for the BET procedure may then give quite erroneous values for the surface area. If the pores are rather larger—tens to hundreds of Angstroms in width—the pore size distribution may be calculated from the adsorption isotherm of a vapour with the aid of the Kelvin equation, and within recent years a number of detailed procedures for carrying out the calculation have been put forward but all too often the limitations on the validity of the results, and the difficulty of interpretation in terms of the actual solid, tend to be insufficiently stressed or even entirely overlooked. And in the time-honoured method for the estimation of surface area from measurements of adsorption from solution, the complications introduced by... 

Based on these observations, criticize or defend the following proposition Except for two of the values in MEK, the reproducibility of M determinations is quite acceptable. MEK consistently gives erroneous values, probably because the solutions are highly nonideal for this solvent, which is more polar than either benzene or toluene. 

Tank/soil potential measurements cannot be made on objects to be protected with very high coating resistances which are found in rare cases of defect-free coating, and particularly with resin coatings. Off potentials change relatively quickly with time, similar to the discharge of a capacitor, and show erroneous values that are too positive [8]. This is the case with coating resistances of 10 Q m. If there are defects, the resistance is clearly much lower. The advice in Section 3.3.2.2 is then applicable for potential measurement. 

There are two main reasons for the failure to obtain a correlation. The first is the use of erroneous values for x, especially for the hydrogen atom. 

Objections were raised to other results of these authors derived by viscometric techniques. Thus the viscometric technique led to the erroneous value 119) of 1, instead of 4, as required by symmetry, for the equilibrium constant of the athermal exchange l20> ... 

Kinetic data exist for all these oxidants and some are given in Table 12. The important features are (i) Ce(IV) perchlorate forms 1 1 complexes with ketones with spectroscopically determined formation constants in good agreement with kinetic values (ii) only Co(III) fails to give an appreciable primary kinetic isotope effect (Ir(IV) has yet to be examined in this respect) (/ ) the acidity dependence for Co(III) oxidation is characteristic of the oxidant and iv) in some cases [Co(III) Ce(IV) perchlorate , Mn(III) sulphate ] the rate of disappearance of ketone considerably exceeds the corresponding rate of enolisation however, with Mn(ril) pyrophosphate and Ir(IV) the rates of the two processes are identical and with Ce(IV) sulphate and V(V) the rate of enolisation of ketone exceeds its rate of oxidation. (The opposite has been stated for Ce(IV) sulphate , but this was based on an erroneous value for k(enolisation) for cyclohexanone The oxidation of acetophenone by Mn(III) acetate in acetic acid is a crucial step in the Mn(II)-catalysed autoxidation of this substrate. The rate of autoxidation equals that of enolisation, determined by isotopic exchange , under these conditions, and evidently Mn(III) attacks the enolic form. 

Measurements can contain any of several types of errors (1) small random errors, (2) systematic biases and drift, or (3) gross errors. Small random errors are zero-mean and are often assumed to be normally distributed (Gaussian). Systematic biases occur when measurement devices provide consistently erroneous values, either high or low. In this case, the expected value of e is not zero. Bias may arise from sources such as incorrect calibration of the measurement device, sensor degradation, damage to the electronics, and so on. The third type of measurement... 

As expected, if the system is still far from steady-state, the method will yield erroneous values for A h- With another set of parameters, the plot of the... 

Note The Q-test administers excellent justification for the outright rejection of abnormally erroneous values however, it fails to eliminate the problem with less deviant suspicious values. 

Carbon paste and graphite epoxy electrodes modified with RUO2 can be used for detection of amino acids and peptides in F1A systems. Optimal conditions are in strongly alkaline solutions at +0.45 V vs Ag/AgCl electrode, with a fast and linear response. Carbon paste electrodes can be modified also with C03O4371. Colorimetric methods for the determination of amino groups attached to a solid support may give erroneous values... 

Most of the terephthalic acid is produced with a catalyst system developed by Scientific Design. It was purchased by Amoco and Mitsui and is referred to as the Amoco Oxidation. The solvent is acetic acid. Compressed air is used as the source for oxygen. The catalyst dissolved in acetic acid and the two reactants are continuously fed into the reactor. The temperature is around 200 °C and the pressure is approximately 25 bar. The reaction is very exothermic (1280 klrnoT1, calculation from data in Stull et al [16] often a much higher, erroneous value is cited). This heat of reaction is removed by evaporation/condensation of acetic acid and can be used in the solvent distillation/purification part of the plant. A scrubber washes the vent gases... 

Kurz and Frieden in 1977 and 1980 determined -secondary kinetic isotope effects for the unusual desulfonation reaction shown in Table 1, both in free solution and with enzyme catalysis by glutamate dehydrogenase. The isotope effects (H/D) were in the range of 1.14-1.20. At the time, the correct equilibrium isotope effect had not been reported and their measurements yielded an erroneous value... 

Selenium and tellurium arc generally considered rare elements and are not found in abundance each, however, has a claim to special interest. The peculiar electrical properties of selenium appeal especially to the physical chemist, but the compounds of this element are of growing importance, especially in their application to the glass industry. Both selenium and tellurium offer attractive fields for research. In the case of tellurium, owing to what had been considered an erroneous value for the atomic weight, the very considerable amount of work done in the past has been too much confined to one direction interest in the chemistry of tellurium appears now to be widening, however. 

Hence, even for an isotope effect as low as 1 %, the specific activity of the residual monomer would increase by about 20%. The enrichment of monomer with radioactive tracer affects the apparent xe values. For example, had the correction not been introduced in the calculation, erroneous values of xe= 5.0 10-7 mole/liter or 1.2 10-7 mole/liter (for / = 0.90 and 0.99, respectively) would be obtained instead of the correct value of xe= 1.0 10 7 mole/liter. 

In the study of mixtures, differentiation between enantiomers is a two level problem which is somewhat independent of whether the LC system is chiral or conventional. The problems common to both systems are the effects of overlapping bands on the performance of the detectorfs). Overlap can be between chiral-achiral species on the one hand and co-eluted chiral-chiral with achiral on the other. On first thought the chiral-achiral distinction should be relatively easy if a chiroptical detector is used because the achiral compounds will not interfere with the detection measurement. In addition the ability of the chiroptical detector to measure both positive and negative signals makes the confirmation of the enantiomeric structure elementary [3,4], As pointed out earlier, enantiomers co-elute from conventional columns and two detectors in sequence will provide the information to measure the enantiomeric ratio provided the mixture is not racemic. Partial or total overlap of the band for a non-chiral species with the chiral eluate band increases significantly the difficulty in measuring an enantiomeric ratio. In this instance the total absorbance that is measured may include a contribution from the non-chiral species which without correction will lead to an overestimation of the amount of chiral material and an erroneous value for the enantiomeric ratio. Under these circumstances there is no other LC option but to develop a separation that is based upon a chiral system. 

A fluorophore free in solution can have a low polarization value, whereas when it is bound to a macromolecule, its polarization increases. The polarization unit is a dimensionless entity, i.e., the value of P does not depend on the intensity of emitted light and the fluorophore concentration. However, this is the theory the reality is quite different. In fact, measuring polarization at high fluorophore concentrations yields erroneous values, and in many cases, instead of reading the correct values of P and A, values that neighbor the limiting values are recorded. 

Due to the formation of an intermediate complex, this type of reaction mechanism was described as being analogous to Michaelis-Menten kinetics [39]. A common error made when examining the behaviour of systems of this type is to use the Koutecky-Levich equation to analyse the rotation speed-dependence of the current. This is incorrect because the Koutecky-Levich analysis is only applicable to surface reactions obeying strictly first-order kinetics. Applying the Koutecky-Levich analysis to situations where the surface kinetics are non-linear, as in this case, leads to erroneous values for the rate constants. Below, we present the correct treatment for this problem based on an extension of a model originally developed by Albery et al. [42]... 

Bundgaard and Jakobsen (82) Bodner and Gaul (83). 6 An erroneous value of 21 Hz is frequently quoted. 

These interferences can be readily overcome by using one of the following techniques (i) The method of additions, (ii) Matching the matrix of the standards with that of the sample, (iii) Solvent extraction to remove the cation to be determined from the interfering matrix, (iv) Relating the erroneous value obtained to an accurate value by using a factor determined by other means. 

At the time these experiments were made an erroneous value for the atomic weight of silver was in use, in consequence of which the value Fe—55-87, in confirmation of that deduced from the oxide analyses, was deduced from the bromide analyses. With the establishment of the modern value for the atomic weight of silver, it accordingly... 

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