Violet Red

Ferric chloride coloration. Add FeCl, solution to a few crystals (or to an aqueous solution) of /> nitrophenol a violet-red coloration is produced. o-Nitrophenol does not give a coloration. 

Place 10 ml. of 1% starch solution (prepared as described above) in a boiling-tube, add 2 ml. of 1% sodium chloride solution and place the tube in a water-bath maintained at 38-40 . Place about 5 ml. of water in a series of test-tubes and to each add a few drops of 1% iodine solution. Now add 4 ml. of the diluted saliva solution to the starch solution, mix well and note the time. At intervals of about 30 seconds transfer 2 drops of the reacting mixture, by means of a dropping tube, to one of the test-tubes, mix and note the colour. As in the previous experiment, the colour, which is blue at first, changes to blue-violet, red-violet, red-brown, pale brown, and finally disappears at this stage the solution will reduce Fehling s solution. If the reaction proceeds too quickly for the colour changes to be observed, the saliva solution should be diluted. 

Colored zones are formed (tin violet-red to blue) on a yellow ochre background... 

Following the 3,4-dihydroisoquinolinium compounds, the isoquino-linium compounds themselves will now be considered. The violet red compound obtained by Zincke by heating i-hydroxy-2-(2,4-dinitro-phenyl)-l,2-dihydroisoquinoline (16a) is the open-chain amino-aldehyde (17) isomeric with (16a) and is not the hemiacetal (18) as assumed by Zincke. This is the first case in which both the members... 

Procedure. Weigh out accurately an amount of the salt which will contain about 0.25 g of chromium, and dissolve it in 50 mL distilled water. Add 20 mL of ca 0.1 M silver nitrate solution, followed by 50 mL of a 10 per cent solution of ammonium or potassium persulphate. Boil the liquid gently for 20 minutes. Cool, and dilute to 250 mL in a graduated flask. Remove 50 mL of the solution with a pipette, add 50 mL of a 0.1 M ammonium iron(II) sulphate solution (Section 10.97, Procedure A), 200 mL of 1M sulphuric acid, and 0.5 mL of /V-phenylanthranilic acid indicator. Titrate the excess of the iron(II) salt with standard 0.02M potassium dichromate until the colour changes from green to violet-red. 

Cascara sagrada or senna—Pink-red, red-violet, red-brown, yellow-brown, or black discoloration of urine may occur. 

Imipramine and its derivatives produce blue, phenothiazines blue, violet, red or orange to skin-colored chromatogram zones, that fade relatively quickly, on a colorless background (Fig. 1). 

The tint plate produces a retardation of about 570 millimicrons, so that the yellow components of white light vanish. The resulting colour of violet-red (or sensitive violef) is changed when an extra retardation is introduced by the strained glass. The eye is very... 

Alternatively, the powder can be placed directly on the strip and the HC1 dropped on it. A violet red or violet blue spot indicates indole derivatives such as LSD. With DMT or psilocybin the color is redder. The color must be observed soon after adding the 1JC1 since it rapidly changes. 

Molecular iodine is a deep violet-red colour. Iodine ions are colourless. Thus, when an antioxidant reduces the iodine molecules in a solution, the iodine colour disappears completely. 

OO A chemist adds a few drops of deep violet-red iodine solution to a vitamin C tablet. The iodine solution quickly becomes colourless. Then the chemist adds a solution that contains chlorine, CI2. The chemist observes that the violet-red colour of the iodine reappears. Explain the chemist s observations, in terms of redox reactions. 

It has been known for a long time that polynitroaromatic compounds produce colored products in contact with aUcafis [1]. These color reactions have been extensively used for the identification of nitroaromatic explosives. In the Janowski reaction [7], a solution of the polynitroaromatic compound (di- or trinitroaromatic) in acetone is treated with concentrated aqueous KOH solution. 1,3,5-Trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT), treated with 30% aqueous KOH, produced violet-red and red colors, respectively. Many variations of the Janowski reaction were reported, using KOH or NaOH in aqueous or ethanoHc solutions as reagents, and dissolving the explosives in acetone, ethanol or acetone-ethanol mixture [3,8]. The reaction was used both for spot tests and for spraying TLC plates [9]. 

The formation of furoin from furil represents the simplest and quickest demonstration of phytochemicai reduction for lecture purposes. The presence of the acyloin can be demonstrated, even in extreme dilution, by its characteristic reaction with aqueous or alcoholic sodium hydroxide (deep blue-green color with deep violet-red dichroic irridescence). This reaction can be carried out in unfiltered fermentation mixtures it gives positive results after thirty seconds. The addition of a few crystals of commercially available furil dissolved in one cc. alcohol to a fermenting sugar solution is suflBcient for demonstration. ... 

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