Migration of colours

Detection of the end-point depends on the fact that anionic surfactants react with some cationic dyestuffs, and cationic surfactants with some anionic dyestuffs, to form salts which, while not particularly insoluble in water, can be extracted with chloroform. Over the last 50 years, many methods have been proposed which are all variants on the general idea of titrating an anionic with a cationic, or vice versa, in a chloroform-water system in the presence of an ionic dyestuff, the end-point being disclosed by the migration of colour from water to chloroform or vice versa. One of these variants [5] was developed at the behest of the Commission Internationale d Analyses, and a critical review [6] was published two years later. These two papers repay close study. 

Four aspects of migration of colour from plastic materials may be identified contact bleed, bloom, plate-out and solvent bleed, all of which are associated to a certain extent with solubility of the pigment in the polymer. Contact bleed occurs when a coloured plastic material... 

AVERAGE MIGRATION TIMES AND CONTENTS OF COLOURANTS DETERMINED IN COMMERCIAL FOOD SAMPLES... 

ISO 105-X10 Textiles - Tests for colour fastness - Part XIO Assessment of migration of textile colours into polyvinyl chloride coatings ISO 264 1976 Unplasticized polyvinyl chloride (PVC) fittings with plain sockets for pipes under pressure - Laying lengths - Metric series ISO 265-1 1988 Pipes and fittings of plastics materials - Fittings for domestic and industrial waste pipes - Basic dimensions Metric series - Part 1 Unplasticized poly(vinyl chloride) (PVC-U)... 

The migration of water in teeth was tried to be visualized using fuchsine dye as a colorant ([103], rosaniline hydrochloride C19H17N3 HCI). Fresh human molars were immersed into a slightly acidic aqueous fuchsine solution. As was expected, the water penetrated fast via the nerve canal into the pulpa and especially the roots were dyed red from fuchsine migrating inwards as well from the sample surface as from the nerve canal. After several days, it could be observed that water had migrated into the gap between the enamel and the dentine (edj). Generally the intensity of the colour increased with time, and the dentine took up the colour more readily than the enamel. 

Three mechanisms can be considered for the migration of an ink vehicle such as oil capillary imbibition, spreading, and bulk diffusion. It takes about 100 ms for a fresh print to travel from one nip of the printing press to the next in a commercial multicolor printing press. In this time the oil vehicle is sufficiently drained from the ink that set off does not occur in the second colour unit. The driving force for capillary imbibition is surface tension ... 

Figure 2. Glass fibre open-strip electrophoresis ofpigment C-II, Afv and vitisin A at pH 2.2. The right hand side of each electrophoretogram is stained with silver nitrate to reveal the migration of the non-colored standards, neutral fructose and single positively charged glucosamine. Mv and pigment C-II appear as red spots whereas vitisin A is coloured orange at this pH.

Fig. 5.27 Silver bromide adopts an NaCl lattice, (a) An ideal lattice can be described in terms of Ag ions occupying octahedral holes in a cubic close-packed array of bromide ions, (b) A Frenkel defect in AgBr involves the migration of Ag ions into tetrahedral holes in the diagram, one Ag+ ion occupies a tetrahedral hole which was originally vacant in (a), leaving the central octahedral hole empty. Colour code Ag, pale grey Br, gold.

The risk of migration of metallic substances used in the formulation of metallic materials (alloying elements or impurities) must be assessed with r ard to their toxicity and also for possible impact on organoleptic quality of drinking water (odour, colour and turbidity). 

DS/EN ISO 105-X10 1996 Textiles - Tests for colour fastness - PartXlO Assessment of migration of textile colors into polyvinyl chloride coatings... 

In 1850, F. Runge published his book "Zur Farbenchemie. Musterbilder fur Freunde des Schonen und zum Gebrauch fiir Zeichner, Maler, Verzierer und Zeugdrucker" (On colour chemistry. Examples for lovers of beauty and for use by artists, painters, ornamenters and cloth printers), in which he described for the first time the migration of various dyes on paper using water as an eluent. 

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