General interpretation considerations

Both ESI and APCI spectra can look relatively simple in most cases, just showing the pseudo-molecular ion MH or adduct ion in the positive mode, and deprotonation or adduct ions in the negative mode. With API techniques we are dealing with even-electron (non-radical) MH ions as opposed to odd-electron M species that result from electron ionisation. Once an ion has achieved an even-electron state, it is unlikely to revert to an odd-electron state, as this is energetically unfavourable. This means that fragmentations from MH should 

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The three criteria for predicting cation ordering, based on ionic radii, crystal field stabilization energy and site distortion, while being useful for qualitatively explaining intersite distribution patterns of transition metals and related elements, have been critically evaluated (e.g., Brown, 1982). These assessments have highlighted additional criteria that need to be taken into consideration in more general interpretations of cation order-disorder behaviour in minerals. These criteria are based on ionicity-covalency relationships. 

The K20/Na20 ratio of sediments and continental basement increased considerably at about the Archean/Proterozoic transition (Figure 18), as already pointed out by Engel et al. (1974). Subsequently, Taylor (1979) and Taylor and McLennan (1985) emphasized that the REE showed similar trends in their overall concentrations, in LREE/HREE and Yb/La ratios, and in the decline of the size of the europium anomaly. The general interpretation of these data was based on the proposition that the compositions of the continental crust, and of continental sediments, reflect a major cratonisation event that spanned... 

The recent ACS publication Excited States and Reactive Intermediates contains three chapters on this topic. Until recently, photochemists had generally interpreted the substitution reactions of excited states of Cr(III) complexes in terms of dissociative mechanisms, but as a result of pressure dependence studies and the extensive data on the photoinduced water exchange in the 18 possible [Cr(NH3)jc(OH2)6-x] ions, more consideration is being given to... 

Photo-oxidation kinetics of polymers are generally interpreted in terms of free-radical reactions (cf section 2.1). The determination of rate constants for these reactions has been the subject of extensive studies and considerable disagreement still exists as to their absolute values (particularly in solid polymers). 

In quantum theory, physical systems move in vector spaces that are, unlike those in classical physics, essentially complex. This difference has had considerable impact on the status, interpretation, and mathematics of the theory. These aspects will be discussed in this chapter within the general context of simple molecular systems, while concentrating at the same time on instances in which the electronic states of the molecule are exactly or neatly degenerate. It is hoped... 

The review and interpretation of toxicology studies is a professional matter, requiring experience in both the laboratory conduct of such studies and the practice of appHed toxicology. Although all studies should be reviewed on a case-by-case basis, there are some general considerations to be kept in mind during the review process, described below. 

The optical rotatory dispersion curves of steroidal ketones permit a distinction to be made between the conformations, and assignment of configuration is possible without resorting to chemical methods (see, e.g. ref. 36) which are often tedious. The axial halo ketone rule and, in the more general form, the octant rule summarize this principle and have revealed examples inconsistent with the theory of invariable axial attack in ketone bromination. 2-Methyl-3-ketones have been subjected to a particularly detailed analysis. There are a considerable number of examples where the products isolated from kinetically controlled brominations have the equatorial orientation. These results have been interpreted in terms of direct equatorial attack rather than initial formation of the axial boat form. 

The interpretation of these remarkable properties has excited considerable interest whilst there is still some uncertainty as to detail, it is now generally agreed that in dilute solution the alkali metals ionize to give a cation M+ and a quasi-free electron which is distributed over a cavity in the solvent of radius 300-340 pm formed by displacement of 2-3 NH3 molecules. This species has a broad absorption band extending into the infrared with a maximum at 1500nm and it is the short wavelength tail of this band which gives rise to the deep-blue colour of the solutions. The cavity model also interprets the fact that dissolution occurs with considerable expansion of volume so that the solutions have densities that are appreciably lower than that of liquid ammonia itself. The variation of properties with concentration can best be explained in terms of three equilibria between five solute species M, M2, M+, M and e ... 

While the few examples quoted provide some general guidance as to the behaviour of nickel-rich materials in contact with molten metals and salts, it cannot be over-emphasised that such behaviour can be very considerably modified by the presence of very small amounts of contaminants in the liquid media (see Sections 2.9 and 2.10). The effect of very small contents of sodium chloride on the corrosion of nickel-base alloys by sodium sulphate has been referred to previously and other reported examples involving trace amounts, particularly of gaseous impurities, underline the need for great care in interpretation of experimental results. 

The nature of the termination reaction in MMA polymerization has been investigated by a number of groups using a wide range of techniques (Tabic 5.5), There is general agreement that there is substantial disproportionation. However, there is considerable discrepancy in the precise values of k tk. In some cases the difference has been attributed to variations in the way molecular weight data are interpreted or to the failure to allow for other modes of termination under the polymerization conditions (chain transfer, primary radical termination).154 In other eases the reasons for the discrepancies are less clear. MALDI-TOF mass... 

In a DTA study [1193] of decomposition reactions in Ag2C03 + CaC03 mixtures, the presence of a response peak, absent on heating the silver salt alone, resulted in the identification of the double salt Ag2C03 2 CaC03, stable at <420 K. One important general consideration which arises from this observation is that the formation of a new phase, by direct interaction between the components of a powder mixture, could easily be overlooked and, in the absence of such information, serious errors could be introduced into attempts to formulate a reaction mechanism from observed kinetic characteristics. Due allowance for this possibility must be included in the interpretation of experimental data. 

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