Colour measurement structure

Few well-defined Con-carbonate complexes are known. The two structures given in Table 68 are probably representative of chelated and monodentate carbonate. K2[Co(C03)2(H20)4] crystallizes as rose-coloured plates from warm solutions of Co 1 salts in the presence of K2C03s7° and contains trans monodentate carbonate. Bidentate carbonate in [Co(C03)(H20)2(imH)2] appears to exert a measurable structural tram influence on the trans water molecules (CoO, 216.6 pm vs. 209.4 in Co(H20)5+)330 and a similar effect is found in Coin-carbonato complexes. Violet crystals of [Co(C03)(H20)2(NHpy2)] have been isolated on reacting Na3[Co(C03)3] with 2,2 -bipyridylamine and presumably contain chelated carbonate (IR n = 5.23 BM).871... 

This chapter has attempted to present the basics of colour measurement as applied to foods. It is important to realise that the wide variability in the nature of foods and food products, from both their structure and pigmentation, may limit any colour measurement technique applicable only to that particular food. This is because the numeracy of the data is unlikely to match the visual experience of equivalent reference atlas colours. In some cases this discrepancy may be large and has to be recognised as an intrinsic property of the food. These differences may arise from the difference of the visual experience of the product when viewed under normal lighting conditions as opposed to the limitations of its optical properties when presented to the particular colour-measuring instrument. This is... 

Three examples using calibrated equipment have been taken to illustrate the problems and potential solutions for the measurement of elements of total appearance. The first describes the appearance of ripening banana, the second the colour and structure of a breakfast cereal, the third the gloss of an orange. 

Measurements of electronic absorption spectra in the visible region not only lead to the evaluation of CFSE s, but they also provide useful information about the crystal chemistry of transition metal ions in the crystal structures and causes of colour and pleochroism of minerals. In this chapter, techniques for measuring absorption spectra of minerals are briefly described and some general applications of the optical spectra to basic crystal chemical properties, such as colour and pleochroism, are discussed. These examples also amplify many of the features of crystal field spectra outlined in chapter 3. 

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