Subject violet

Most mordant dyes are monoazo stmctures. The most important feature of this class of dyes is excellent fastness to light and washing. Mordant dyes are available ia aU shades of the spectmm with the exceptioa of bright violets, blues, and greens. To be useful, the metal complexes must be stable, ie, must not demetallize when subjected to dyebath conditions and aU aftertreatment processes, especially repeated washings. Chromium forms stable chelate rings with mordant dyes which are not affected by treatment with either weak acid or alkaU (see Coordination compounds). 

The deep violet color of pentaphenylbismuth and certain other pentaarylbismuth compounds has been the subject of considerable speculation. It has been shown by x-ray diffraction (173) that the bismuth atom in pentaphenylbismuth is square—pyramidal. WeU-formed crystals are dichromic, appearing violet when viewed in one plane but colorless in another plane. The nature of the chromophore has been suggested to be a charge-transfer transition by excitation of the four long equatorial bonds ... 

Dioxazine Violet. Carba2ole Dioxa2ine Violet is prepared by the reaction of two moles of 2-ainino-A/-ethylcarba2ole with chloranil. This violet may be used in most plastics for shading phthalocyanine blues, because it has comparable light fastness. At relatively high temperatures, it may be subject to slow decomposition. 

Lower oxidation states are rather sparsely represented for Zr and Hf. Even for Ti they are readily oxidized to +4 but they are undoubtedly well defined and, whatever arguments may be advanced against applying the description to Sc, there is no doubt that Ti is a transition metal . In aqueous solution Ti can be prepared by reduction of Ti, either with Zn and dilute acid or electrolytically, and it exists in dilute acids as the violet, octahedral [Ti(H20)6] + ion (p. 970). Although this is subject to a certain amount of hydrolysis, normal salts such as halides and sulfates can be separated. Zr and are known mainly as the trihalides or their derivatives and have no aqueous chemistry since they reduce water. Table 21.2 (p. 960) gives the oxidation states and stereochemistries found in the complexes of Ti, Zr and Hf along with illustrative examples. (See also pp. 1281-2.)... 

If the proplnt is double-base, it has been observed that even the most stable propints bleach methyl violet paper in much shorter periods than one year. Investigations conducted by P.F. Macy at Picatinny Arsenal (Ref 4) showed that diphenylamine-stabilized doublebase proplnts in service storage at about 30°, may be considered of satisfactory stability if they do not cause complete bleaching of 0.1 N methyl violet paper in one month or less. Such proplnts always show satisfactory stability when subjected to the 65.5° Surveillance Test. It was observed at the same time, that double-base proplnts which had deteriorated, but were not yet hazardous, took from 11 to 24 days to bleach methyl violet paper at 30°... 

Visual judgement of whiteness is highly subjective. Many factors, such as the observer s age, sex and colour perception, and even the hue of white materials normally encountered in the observer s country, help to decide on individual preference for either a red-violet or a... 

The experiments on the iodine separation were conducted as follows. A tubular vessel of pyrex glass, having at one end a plane window and at the other end a conical light-trap, was evacuated and then filled with iodine at about 0.17 mm. pressure, and then with hexene at about 6 mm. partial pressure. The tube was then subjected to the intense light from two Cooper-Hewitt glass mercury arcs, using a filter of 0.05 molal potassium dichromate 2 cm. in thickness to cut off all radiations on the violet side of the green mercury line. The lamps were rim at considerably below the rated capacity, and were cooled by a blast of air to keep the emission lines as narrow as possible. 

Finally,- the alkali salts of phenol itself are more deeply coloured than is phenol. This fact cannot indeed be recognised subjectively, but investigation of the absorption of ultra-violet light demonstrates it. Thus it has been found that the absorption by sodium phenoxide much more nearly approaches the subjectively visible part of the spectrum than does that of the free phenol. The difference is so considerable that it provides also a satisfactory explanation of a subjectively perceptible deepening of colour from colourless to yellow. The colour of the salts of nitrophenols is therefore ascribed to the bathychromic (colour-deepening) efEect of salt-formation. 

Mixed with NaOH solution and distilled distillate analyzed for ammonia by titration, colorimetry, or electrode method (see Ammonia and Ammonium chloride). Bromide portion of NH4Br in aqueous solution may be analyzed by ion chromatography, or by the colorimetry method in which red to violet color is produced upon treatment with chloramine-T, and phenol red at pH 4.5. The colorimetry test for bromide is subject to interference from oxidizing and reducing agents, chloride, and bicarbonate. NH4Br may then be determined stoichiometrically. 

A portion of the solution was subjected to a qualitative electrical migration experiment using a three-component cell similar to that described by Hardwick and Robertson (79). The solution under investigation was placed in the center compartment, and in the outer compartments were placed sulfuric acid solutions of concentrations similar to that of the test solution. No diffusion occurred over a period of 24 hours. Application of about 50 volts d.c. across the electrodes caused migration of violet color to the cathode and no violet color to the anode. The results indicate a positively charged chromium species. 

Following extraction, the primary sample extract is subsequently subjected to some type of cleanup including conventional liquid-liquid partitioning and/ or solid-phase extraction. The liquid-liquid partitioning cleanup applied differs with the initial extraction system. Thus, for isolating fat from analytes, the primary dichloromethane sample exttact was partitioned with IN hydrochloric acid in the analysis of leucogentian violet in chicken fat (491-494). The acidic layer was then neutralized with trisodium citrate to facilitate back extraction of the analytes into dichloromethane. 

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