Colouration selection

Bridle P and Timberlake CF. 1997. Anthocyanins as natural food colours-selected aspects. Food Chem... 

In colour vision there are three specific types of cone cell corresponding to red, green and blue receptors. The chromophore is the same for all three colours, being 11-cis-retinal bound to a protein which is structurally similar to opsin. Colour selectivity is achieved by positioning specific amino acid side chains along the chromophore so as to perturb the absorption spectrum of the chromophore. 

As mentioned above, Ceran glass ceramic cooktops are decorated with ceramic colours of varying chemical composition (to achieve the extensive colour selection - currently 17 different tints). 

Non-soap greases using finely divided solids as thickeners are useful as lubricants at elevated temperatures. Materials used include organO Clays such as dimethyldioctyl-decyl-ammonium bentonite (Bentone greases) or selected dyestuffs which produce brightly coloured greases. 

For coloured product family selection is made on nickel-chromium specimen of 30 pm, but for fluorescent product family selection is made on nickel-chromium specimen of 10 pm. Tests made on real defects confirm these results. 

The general task is to trace the evolution of the third order polarization of the material created by each of the above 12 Raman field operators. For brevity, we choose to select only the subset of eight that is based on two colours only—a situation that is connnon to almost all of the Raman spectroscopies. Tliree-coloiir Raman studies are rather rare, but are most interesting, as demonstrated at both third and fifth order by the work in Wright s laboratory [21, 22, 23 and 24]- That work anticipates variations that include infrared resonances and the birth of doubly resonant vibrational spectroscopy (DOVE) and its two-dimensional Fourier transfomi representations analogous to 2D NMR [25]. 

The unique feature in spontaneous Raman spectroscopy (SR) is that field 2 is not an incident field but (at room temperature and at optical frequencies) it is resonantly drawn into action from the zero-point field of the ubiquitous blackbody (bb) radiation. Its active frequency is spontaneously selected (from the infinite colours available in the blackbody) by the resonance with the Raman transition at co - 0I2 r material. The effective bb field mtensity may be obtained from its energy density per unit circular frequency, the... 

A mixture can often be separated into its components by utilising their selective adsorption from solution by a suitable substance, such as active alumina the separation can be readily followed if the components are coloured. 

The nitrosamines are insoluble in water, and the lower members are liquid at ordinary temperatures. The separation of an oily liquid when an aqueous solution of an amine salt is treated with sodium nitrite is therefore strong evidence that the amine is secondary. Diphenylnitrosoamine is selected as a preparation because it is a crystalline substance and is thus easier to manipulate on a small scale than one of the lower liquid members. For this preparation, a fairly pure (and therefore almost colourless) sample of diphenyl-amine should be used. Technical diphenylamine, which is almost black in colour, should not be employed. 

Colour Index name CAS Registry Number Selected manufacturers... 

The differentiation of analytical signal in the photometry enables one to use non-specific reagents for the sensitive, selective and express determination of metals in the form of their intensively coloured complexes. The typical representative of such reagents is 4-(2-pyridylazo)-resorcinol (PAR). We have developed the methodics for the determination of some metals in the drinking water which employ the PAR as the photometric reagent and the differentiation of optical density of the mixture of coloured complexes by means of combined multiwave photometry and the specific destmction of the complexes caused by the change of the reaction medium. 

Development of extraction-free photometric procedures for the determination of traces of metals for which hygienic and environmental regulations have been established is an urgent problem. For solution of this problem we used as an organic reagent l-(2- pyridylazo)-naphtol-2 (PAN) which forms intensely coloured complex compounds with many metals and is frequently used for their extraction-photometric determination however these procedures did not find wide application in water analysis due to lack of selectivity and necessity of using organic solvents. 

During heat dissipation by radiation the colour and condition of the surface plays a similar role. Dark-coloured bodies dissipate more heat than the light-coloured ones. The amount of heat absorption and emission for the same body may therefore be assumed to be almost the same. Accordingly, Table 31.1, for selected colours, may be considered for the coefficients of absorption and emission of heat due to solar radiation and natural radiation respectively. 

Dibenz[yellow-green colour (due to other pentacyclic impurities) has been removed by crystn from benzene or by selective oxidation with lead tetraacetate in acetic acid [Moriconi et al. J Am Chem Soc 82 3441 7960]. 

Select the techniques to be used. Decisions on the number of trials is invariably coloured by cost, but always check they are balanced otherwise it may be false economy... 

Table 9.2 Specific colour codes for selected compressed gases...

Table 10.19 Selected sources of inaccuracy in use of colour detector tubes...

Safe Handling of Colourants 2 Hazard Classification and Selection of Occupational Hygiene Strategies (1993) Safe Handling of Eonnaldehyde (2nd edn) (1995)... 

Requirements for cans for beer and soft drinks differ from those for food cans in that (a) only low tin and iron contents can be tolerated in the product and (t>) the anticipated shelf-lives are much shorter. Specialised lacquering techniques including striping the seams are used to give complete cover to the metal. For soft drinks it is sometimes possible to select colouring matters and acids least likely to give rise to corrosion troubles, and rapid methods of testing formulations have been devised . Steel quality is also controlled by special tests. 

Pigments for finishes are selected on the basis of their colour, but special attention must be paid to inertness in the chosen binder and stability and light fastness under the conditions of application and exposure. Flake pigments such as aluminium and micaceous iron oxide give finishes of lower moisture-vapour permeability than conventional pigments, and consequently contribute to better protection. 

The paint technologist entrusted with the task of formulating a paint to meet a specified set of conditions must first decide what type of binders he should use and the type of solvent blend that this will require. In the particular case of a finish, he must then select the pigments most likely to give the required colour, bearing in mind any limitations imposed by his choice of binder system or by the conditions to which the paint will be subjected. 

Many of the heavy metals give slightly soluble products (some white, some coloured) with the reagent, most of which are soluble in the organic solvents mentioned. The selectivity of the reagent may be improved by the use of masking agents, particularly EDTA. 

For some purposes it is desirable to have a sharp colour change over a narrow and selected range of pH this is not easily seen with an ordinary acid-base indicator, since the colour change extends over two units of pH. The required result may, however, be achieved by the use of a suitable mixture of indicators these are generally selected so that their pK ln values are close together and the overlapping colours are complementary at an intermediate pH value. A few examples will be given in some detail. 

Some examples of metal ion indicators. Numerous compounds have been proposed for use as pM indicators a selected few of these will be described. Where applicable, Colour Index (C.I.) references are given.12 It has been pointed out by West,11 that apart from a few miscellaneous compounds, the important visual metallochromic indicators fall into three main groups (a) hydroxyazo compounds (b) phenolic compounds and hydroxy-substituted triphenylmethane compounds (c) compounds containing an aminomethyldicarboxymethyl group many of these are also triphenylmethane compounds. 

Calcichrome. This indicator, cyclotris-7-( l-azo-8-hydroxynaphthalene-3,6-disulphonic acid), is very selective for calcium. It is in fact not very suitable as an indicator for EDTA titrations because the colour change is not particularly sharp, but if EDTA is replaced by CDTA (see Section 2.26), then the indicator gives good results for calcium in the presence of large amounts of barium and small amounts of strontium.13... 

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