Colour measurement appearance

Volumetric analysis involves using a solution of accurately known concentration, a standard solution, in a quantitative reaction to determine the concentration of the other reactant. The procedure is known as titration. One solution is measured quantitatively into a conical flask using a pipette. The other solution is dispensed from a burette until a permanent colour change appears in the solution in the conical flask. 

ASTM (1985). American Society for Testing and Materials, colour and appearance measurement, standard method for visual evaluation of gloss differences between surfaces of similar appearance. Philadelphia ASTM D 4449-85. 

ASTM (1994). American Society for Testing and Materials, colour and appearance measurement. Philadelphia ASTM. 

HUTCHINGS J, SINGLETON M, PLATER K AND DIAS B (2001) Food COlour and appearance measurement, specification and communication, can we do better Proceedings International Colour Association, Rochester (forthcoming). 

Metameric Colours. Colours that appear to be the same under one type of illuminant but, because they have different spectral reflectivity curves, will not match under a different illuminant. Two white vitreous enamels may be metameric, for example, if one is opacified with titania in the anatase form whereas the other contains titania in the form of rutile. Methuselah. A 9-quart wine bottle. Methylene Blue Index A simple approximate method for assessing the surface area of a clay. O.OIM methylene blue dye is added to aqueous suspension of clay, in successive small amounts, to determine the least amount of dye required to impart colour to the water suspending the clay. Dye up to this amount is absorbed by the clay, so that this is a measure of the clay s cation exchange capacity (see ionic exchange). For most pottery clays this is proportional to the surface area to a good approximation. ASTM C837 specifies a test for clays. 

The use of colour-measuring instruments allows specification and communication of colour by means of international standard terms such as CIE L a b C h°. Colour difference values can also be determined instrumentally and, if optimized colour difference equations are used, can out-perform a single trained colourist. However, the visual appreciation of colour and colour difference is still a subjective response, affected by many factors. Care must be taken to include measurement conditions in the interpretation of colour measurement data. The gold standard answer must always be that which agrees with the majority of a group of human observers. Whether this can be achieved by optimized equations based on CIE L a b colour space or by colour appearance models remains to be established. 

The number of protons extracted from the film during coloration depends on the width of the potential step under consideration. As can be seen in the formulation of Fig. 26 an additional valence state change occurs at 1.25 Vsce giving rise to another proton extraction. The second proton exchange may explain the observation by Michell et al. [91] who determined a transfer of two electrons (protons) during coloration. Equation (5) is well supported by XPS measurements of the Ir4/ and Ols levels of thick anodic iridium oxide films emersed at different electrode potentials in the bleached and coloured state. Deconyolution of the Ols level of an AIROF into the contribution of oxide (O2-, 529.6 eV) hydroxide, (OH, 531.2 eV) and probably water (533.1 eV) indicates that oxide species are formed during anodization (coloration) on the expense of hydroxide species. The bleached film appears to be pure hydroxide (Fig. 27). 

Slaughter performance (important for butcher) slaughter yield, balanced carcass weight, composition of carcass Meat quality (important for consumer) measurable or sensory meat quality criteria (appearance, colour, tenderness, juiciness, flavour, roast and boil capacity, biochemical values (e.g. pH-value)), and nutritional value... 

Analysis of antioxidant activity by performing a FRAP assay was proposed by Benzie and Strain [23]. It involves colorimetric determination of the reaction mixture in which the oxidants contained in the sample reduce Fe ions to Fe. At low pH, Fe(in)-TPTZ (ferric-tripyridltria-zine) complex is reduced to the ferrous (Fe ) form and intense blue colour at 593 nm can be observed. The FRAP reagent is prepared by mixing 2.5 ml of TPTZ (2,4,6-tris (l-pyridyl)-5-triazine) solution (10 mM in 40mM HCl), 25 ml acetate buffer, pH 3.6, and 2.5 ml FeCl3 H20 (20 mM). The colour of Fe(II)(TPTZ)2 which appears in the solution is measured colorimetri-cally after incubation at 37°C. The measurement results are compared to those of a blank sample, which contains deionised water instead of the analysed sample. The duration of the assay differs from one study to another 4 min [23, 24], 10 min [25] to 15 min [26]. The analysis results are converted and expressed with reference to a standard substance, which can be ascorbic acid [26], FeS04 [23, 25], Trolox [27,18]. 

The crystals dissolve in carbon disulphide and ebullioscopic measurements indicate1 that the molecular formula is As2I4 they also dissolve in ether, alcohol and chloroform. When exposed to air, these solutions darken in colour owing to the formation of the triiodide, and the diiodide cannot be recovered bv evaporation owing to complete decomposition. Boiling acetic anhydride also dissolves the crystals but, on cooling, a yellow substance which appears to contain a derivative of the triiodide separates. The diiodide is also decomposed by pyridine with separation of arsenic, the triiodide being found in solution. 

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