Acid dyes stripping

Uses Dispersant for disperse dyes leveling agent for acid dyes stripping agent for basic dyes Properties Liq. 

Excellent stripping agent for vat, sulphur and direct dyes. Also used when washing off vat, reactive or acid dye prints to prevent staining of white or pale ground. 

It functions as an antiprecipitant in cross dyeing, and as a mild stripping agent and dye leveler for acid dyes. 

Effectively strips acid dyes from nylon. 

The basic dyes differ from all others because they are extracted quite easily by boiling with acetic acid or with alcohol. If, however, these reagents do not remove a substantial portion of the dye from the fibre, the next test is to boil the coloured material in dilute ammonia (1 ml of 0-88 ammonia per 100 ml of water) for 1 to 2 minutes in the presence of white cotton (Clayton, foe. cit.). If the solution is distinctly coloured and the cotton remains unstained, the presence of an acid dye is indicated. This can be confirmed by boiling with 40 per cent of Glauber s salt when a considerable proportion of molecularly-dispersed acid dyeS are stripped, but little effect is apparent with the fast acid dyes. If the cotton is stained the presence of... 

Leather dyes are isolated from the sample by extraction prior to their separation. Samples (100 g cut into strips) of leather that have been dyed can be extracted under reflux for 2-3 h with 100 ml of aqueous 50% dimethylformamide (46,47). Acid dyes from leather are extracted with aq. NH3 solution. The extraction system is based on use of concentration gradient with aq. NHj (47a). 

Uses Emuisifier and dyeing assistant for textiles antiprecipilant to prevent cross-staining stripping agent and dye ieveiing agent for acid dyes Features Hydrophiiic Pmperties Liq. HLB 16.4 100% act. 

Uses Compatibilizer or antiprecipitant in dye bath of acid and cationic dyes mild dye Ieveier and/or stripping agent for acid dyes hydrophilic emulsifier skin and hair care prods. 

A less accurate but more colorful way to measure pH uses a universal indicator, which is a mixture of acid-base indicators that shows changes in color at different pH values (Figure 13.5, p. 359). A similar principle is used with pH paper. Strips of this paper are coated with a mixture of pH-sensitive dyes these strips are widely used to test the pH of biological fluids,... 

Non-destructive partial stripping techniques for basic dyes on acrylic fibres are carried out at 100 °C (or higher if possible) using, for example, 1-10% o.w.f. anionic retarder and 1 g/1 acetic acid (60%), or 1-5 g/1 Marseilles (olive oil) soap. Destructive stripping requires acidified (pH 5.5-6.0) sodium hypochlorite, followed by an antichlor treatment in sodium dithionite or sodium bisulphite. In some cases a preliminary boiling treatment in 5 gA monoethanolamine and 5 g/1 sodium chloride is said to improve the effect of the stripping treatment. 

Calcobond dyes was that the colour fastness to light was adversely affected. The fastness to acid treatment was no better than that of the resin finish, i.e. the dyeings could be stripped by boiling at a pH below 5. 

The first work on pKa determination by zone electrophoresis using paper strips was described by Waldron-Edward in 1965 (15). Also, Kiso et al. in 1968 showed the relationship between pH, mobility, and p/C, using a hyperbolic tangent function (16). Unfortunately, these methods had not been widely accepted because of the manual operation and lower reproducibility of the paper electrophoresis format. The automated capillary electrophoresis (CE) instrument allows rapid and accurate pKa determination. Beckers et al. showed that thermodynamic pATt, (pATf) and absolute ionic mobility values of several monovalent weak acids were determined accurately using effective mobility and activity at two pH points (17). Cai et al. reported pKa values of two monovalent weak bases and p-aminobenzoic acid (18). Cleveland et al. established the thermodynamic pKa determination method using nonlinear regression analysis for monovalent compounds (19). We derived the general equation and applied it to multivalent compounds (20). Until then, there were many reports on pKa determination by CE for cephalosporins (21), sulfonated azo-dyes (22), ropinirole and its impurities (23), cyto-kinins (24), and so on. 

Urea in kidney dialysate can be determined by immobilizing urease (via silylation or with glutaraldehyde as binder) on commercially available acid-base cellulose pads the process has to be modified slightly in order not to alter the dye contained in the pads [57]. The stopped-flow technique assures the required sensitivity for the enzymatic reaction, which takes 30-60 s. Synchronization of the peristaltic pumps PI and P2 in the valveless impulse-response flow injection manifold depicted in Fig. 5.19.B by means of a timer enables kinetic measurements [62]. Following a comprehensive study of the effect of hydrodynamic and (bio)chemical variables, the sensor was optimized for monitoring urea in real biological samples. A similar system was used for the determination of penicillin by penicillinase-catalysed hydrolysis. The enzyme was immobilized on acid-base cellulose strips via bovine serum albumin similarly as in enzyme electrodes [63], even though the above-described procedure would have been equally effective. 

Hsu D, Hoffman P, Mashburn (1972) Micro colorimetric method of dye staining and its application to cellulose polyacetate strip electrophoresis for the determination of acid glycosaminoglycans. Anal Biochem 46 156-163... 

Stripping test for acid colours. Some direct or " salt dyestuffs are partly decolorised by dilute ammonia and hence might be regarded as add colouring matters. To avoid this error it is useful to add, when this test is made, a piece of mercerised white cotton. With an add dye, the cotton remains white, or is scarcely coloured, and then becomes white again when boiled a second time with dilute ammonia. 

It can be prepared either by using appropriate direct dyes or reactive dyes. In the latter case, pure linters (the raw material for high-quality paper) are suspended in water, and the solution of the reactive dye is added. For example, the dye 15 reacts via the sulfonic acid group in the side chain. The reaction mixture is then made alkaline and the dye reacts with the linters. After completion of the reaction, the fiber pulp is centrifuged, washed electrolyte-free, and processed on a paper machine to form the pH paper. Paper produced in this way is mostly bonded onto a plastic material and used as pH test strip. 

In order to strip the dyes of madder dyeings completely from the fiber, they must be extracted in acid solution at temperatures up to roughly 100° C. Comparative solutions produced by extraction from dyer s plants such as madder root must also be prepared in the same manner at acid pH for the TLC. The anthraquinone dyes are present in the dyer s plants partly in the form of glycosides. These glycosides must be split hydrolytically with acids in order to obtain for the TLC a comparative solution that contains only free hydroxyanthraqui-nones and no hydroxyanthraquinone glycosides. 

When we strip a red dyeing by the improved extraction method with a mixture of 10% sulfuric acid and ethyl acetate (1 1) and.the upper layer has a yellow or orange-yellow shade and the lower layer is colorless, we can assume that this is a madder dyeing. 

When the improved method of extraction is used for stripping madder dyes with 10% sulfuric acid and ethyl acetate (see page 202), and the ethyl acetate layer is not stained yellow, but orange, this could indicate the presence of insect dyes containing kermesic acid (XXVI). 

Values of pH from 1 to 6 are termed acidic and 7 as neutral, whereas alkaline solutions have values of 8-14. Coloured solutions called indicators have been specially made to change colour when added to solutions of different pH values. This colour change is a rough indication of the pH of a solution, and paper strips containing these dyes can be used as test strips to check the pH of solutions. 

Perspiration tests similarly indicated the presence of two dyestuffs. In the alkali solution, the yellow color seemed to be removed almost completely, leaving a pink-colored fabric. In the acidic solution, the yellow dye migrated to the wool, silk, and nylon sections of the multifiber test strips, staining these fibers a bright yellow shade. The pink color seemed to bleed minimally a small amount of color was transferred in the alkali solution tests, but generally this pink color remained comparatively very fast. 

Litmus Paper. This is an indicator for all acids and bases, weak or strong. Acids turn it red, bases blue. In preparing litmus. paper, only the best litmus is used. The cubes, which contain from 50 to 90 per cent of gypsum, are broken up and extracted once with alcohol. The dye is then dissolved in water, 4 to 5 grams per liter, and pure filter paper is soaked in the solution. The sheet is suspended on a cord to dry and is then cut into thin strips. For red litmus paper, a few drops of acetic acid is added to the solution, and for blue litmus paper, a few drops of ammonia. The less pronounced the color of the paper, the more sensitive it is. 

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