Showing papers on "Color reaction published in 1970"

Color Reactions of Poly vinyl Acetate and Its Derivatives with Iodine

Abstract: It has been found that the addition of a methanol solution containing polyvinyl acetate (PVAc) and iodine to an aqueous solution of potassium iodide results in a red-violet color without precipitating any polymer. The absorption maximum was located at 510 mμ. The absorbance of the PVAc-iodine complex decreased only slightly with an increase in the degree of the polymerization of PVAc. A linear relationship was obtained between the abosrbance and the PVAc concentration. It was found from these results that the color reaction of PVAc with iodine can be used in a colorimetric determination of PVAc, which is insoluble in water. Further, an attempt was made to investigate the complex formation of the vinyl acetate-vinyl propionate copolymer (PVAc-PVPr) and the vinyl acetate-vinyl formacetal copolymer (PVAc-PVFA) with iodine. Although the absorption maximum of the color complex of PVAc-PVPr with iodine appeared at 510 mμ, independent of the copolymer composition, the absorbance decreased with an increase in the...

Microdetermination of ascorbic acid and tryptophan by colorimetry.

Abstract: Ascorbic acid reacts with 2,3,5-triphenyltetrazolium chloride in alkaline medium giving pink color having 5μg/ml as visual limit of identification. This color reaction has been utilized for the colorinietric determination of ascorbic acid from pharmaceutical preparations in minute quantities. The maximum tolerable amount of other vitamins, sugars and organic compounds during determination of ascorbic acid is reported.

The question of triazenes in the total color effect of the protein AZO coupling reaction in histochemistry.

Abstract: The suggestion that triazenes formed by union of alkalized diazonium salts with aliphatic amino groups contribute to the azo color reaction of tissue proteins is rejected. Deaminations of formaldehyde-fixed and other tissues were sufficient to render the previously oxyphil elements of these tissues basophilic to azure A-eosin B at the same pH level. After these deaminations there was no detectable difference in intensity or distribution of the azo coupling reaction. Freshly diazotized safranin 0, dimethylphenosafranin (methylene violet) and the diazosulfanilic acid, azure A sequence technic were used as testing methods. Acid extraction even when prolonged to 24 hr and when acid concentration raised from 0.1 N to 0.24 N does not alter the intensity or distribution of the several azo coupling reactions as compared with unextracted preparations. Deliberate creation of triazenes by admixture of proline, diethylamine, hydroxylamine, hydrazine sulfate, glycine and uric acid, added to the diazo in stoichiometric excess, more or less completely inhibited azo coupling of all tissue elements. Uric acid and hydrazine were the most eflective, and then hydroxylamine, proline and diethylamine in that order. Reacidification of the uric acid compound to pH 2.2-2.5 for 10 mm, filtration to remove liberated uric acid and realkalinization moderately restored the azo coupling capacity of diazosafranin. This illustrates acid destruction of a triazene of this diazotate. It is concluded that triazenes with tissue aliamino groups play no significant part in the final color effect of azo coupling with the diazonium

Mechanism of the Color Reaction of Active Methylene Compounds with 1, 3, 5-Trinitrobenzene Derivatives. I. Crystalline Products of the Color Reaction of Acetone with 1, 3, 5-Trinitrobenzene (Organic Analysis. LXXI)

Abstract: Two coloring matters produced in the color reaction of acetone with excessive 1, 3, 5-trinitrobenzene in an alkaline medium were separated in crystalline forms and one of them was determined as the Meisenheimer type complex of acetone (I). The other was a new type complex (II) and was characterized as a sodium salt of the anion group shown in Chart 1. Spectrophotometric studies of I, II and the color reaction showed that I formed in the early stage of the reaction and then changed to II with time in the alkaline medium in the presence of excessive trinitrobenzene. In addition, a reason for increase of the color intensity in the improved procedures of the detection and determination of acetone was clarified by studying spectrophotometrically some behaviors of I and II.

A modified method of the prussian blue reaction for the histochemical demonstration of iron, and its application to the colloidal iron reaction of acid mucopolysaccharides

Abstract: In the Prussian Blue method for the histochemical demonstration of iron, some parts of produced pigment are considerably washed away during the dyeing process, because the pigment is water soluble. Consequently decrease and diffusion of the pigment occur and staining of the surrounding tissues take place. The color reaction was carried out in 70% acetone solution in order to decrease the solubility of the pigment. Obtaining the sharp and clear demarcation, this method was applied successfully to the colloidal iron reaction of acid mucopolysaccharides and very strong and clear reaction was obtained.

Spectrophotometric determination of mercury (II) by solvent extraction with variamine blue B.

Abstract: A new rapid, sensitive and selective method is proposed for the spectrophotometric determination of a trace of mercury (II) by solvent extraction. The method is based on the formation of an ion-pair complex between the tribromo-mercury(II) complex anion and the dyestuff cation obtained by oxidation of variamine blue B. The optimum pH range for the color reaction is 2.5–4. The blue complex can be extracted into nitrobenzene and has a maximum absorption at 605 mμ in the organic solvent. Beer’s law holds in the range 3.2×10−6−2.2×10−5 M of mercury(II) in the aqueous layer before the extraction, with a molar absorptivity of 4.03×104 mol−1cm−1 l at 605 mμ. The color reaction is instantaneous and the complex remains stable 15 mintes in the nitrobenzene layer. Of the 22 cations and 11 anions examined, tin(II), tin(IV), antimony (III), iodide, cyanide, and thiocyanate showed serious interferences.

A colorimetric method for the micro determination of 2-phenylphenol

Abstract: A colour reaction produced with the fungicide 2-phenylphenol is described. 2-Phenylphenol, its esters and sodium 2-phenylphenate give a pink colour with concentrated sulphuric acid and traces of formaldehyde and iron(III), which is specific for 2-phenylphenol. With 5 ml of reagents, 1 µg of these compounds produces colours that are discernible visually. In fixed conditions the reaction conforms to the Beer-Lambert law for up to 16 µg of 2-phenylphenol per 5 ml of reagents. A simple and rapid method has been evolved for its determination in disinfectant solutions containing sodium 2-phenylphenate, and in paper wrappers impregnated with 2-phenylphenol, its esters or its sodium salt. Recovery varies from 94·1 to 105·0 per cent.; the deviations remain within the limits of experimental error.

Colorimetric determination of gold(III) using 3-methyl-4-vanillidine isoxazolone-5

Abstract: A new color reaction for the determination of gold(III) has been developed. Gold reacts with 3-methyl-4-vanillidine isoxazolone-5 in basic media at 90° to produce a pink color which is specific. Cobalt and nickel do not interfere when present upto 4 folds. Maximum tolerable amounts of other metal ions have also been studied.