Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Purple colorants

Reactions of Aspirin, (i) Distinction from Salicylic acid. Shake up with water in two clean test-tubes a few crystals of a) salicylic acid, (0) aspirin, a very dilute aqueous solution of each substance being thus obtained. Note that the addition of i drop of ferric chloride solution to (a) gives an immediate purple coloration, due to the free —OH group, whereas (b) gives no coloration if the aspirin is pure. [Pg.111]

Dissolve ca. 0 2 g. of product (I) in cold ethanol, and add with shaking 1-2 drops of dilute sulphuric acid. A deep purple coloration appears at once. This shows that salt formation has occurred on the quinoline nitrogen atom to form the cation (Ha), which will form a resonance hybrid with the quinonoid form tils). [Note that the forms (IIa) and (11b) differ only in electron position, and they are not therefore tautomeric.] If, hoAvever, salt formation had occurred on the dimethylaniino group to give the cation (III), thrs charge separiition could not occur, and the deep colour would be absent. [Pg.303]

Sulphur. THE LASSAIGNE SODIUM TEST. The sodium fusion will have converted any sulphur present in the original compounds to sodium sulphide. Dissolve a few crystals of sodium nitroprusside, Na8[Fe(CN)5NO],zH20, in water, and add the solution to the third portion of the filtrate obtained from the sodium fusion. A brilliant purple coloration (resembling permanganate) indicates sulphur the coloration slowly fades on standing. Note, (i) Sodium nitroprusside is unstable in aqueous solution and therefore the solution should be freshly prepared on each occasion, (ii) This is a very delicate test for sulphides, and it is essential therefore that all apparatus, particularly test-tubes, should be quite clean. [Pg.325]

NH2CONH2 = NH2CONHCONH2 + NH3 Dissolve the solid residue in a few ml. of warm 10% NaOH solution, cool and add i drop of very dilute copper sulphate solution. A purple coloration is obtained. ... [Pg.362]

Now add a few drops of a freshly prepared solution of sodium nitroprusside. A purple coloration is obtained (test for - SH Group),... [Pg.383]

Murexide test. Place about o-i g. of uric acid in a small evaporating-basin and moisten with 2 3 drops of cone. HNO3. Heat very gently to dryness, and then add i drop of aqueous NHj from a glass rod a purple coloration is produced due to the formation of ammonium purpurate or murexide. Now add a drop of NaOH solution the coloration changes to blue. [Pg.389]

The presence of ammo acids can be detected by the formation of a purple color on treatment with nmhydnn The same compound responsible for the purple color is formed from all ammo acids m which the a ammo group is primary... [Pg.1123]

The diphenylpicrylhydrazyl radical itself is readily followed spectrophotometri-cally, since it loses an intense purple color on reacting. Unfortunately this reaction is not always quantitative. [Pg.353]

Quartz. When colorless, quart2 [14808-60-7] is also known as rock crystal. When irradiated, it becomes smoky from a color center associated with a ubiquitous Al impurity at about the 0.01% level. The name citrine [14832-92-9] is used when quart2 is colored by Fe, and irradiation of this can produce the purple-colored amethyst [14832-91-8] under certain circumstances (2). Although not signiftcandy lower priced than the natural materials, synthetic citrine and amethyst ate used in jewelry because of the abiUty to provide matched sets of stones from large, up to 7-kg, hydrothermaHy grown crystals. [Pg.218]

The Fe(III)0 4 hole color center gives the purple color. On being heated, the trapped electron is released and the reverse of reaction 2 occurs producing Fe(III)0 4, which provides the pale yellow color of citrine. [Pg.223]

From the colorless state it can be switched with light of short wavelength (A = 380 nm) via an electrocycHc ring opening and cis/trans rotation of one half of the molecule into a state with violet/purple color. The reverse reaction is effected by visible light (A = 580 nm). Since the system is metastable, one of the two reaction directions is matched by a rival thermal reaction, the thermoreversion. This progresses, however, in the case of benzospiropyran, at room temperature by a factor of 10 slower than the light-induced reaction. [Pg.151]

The MauIg Color Reaction. The procedure for this test consists basically of three sequential treatments of lignified material with 1% potassium permanganate, 3% hydrochloric acid, and concentrated ammonium hydroxide. A red-purple color develops for hardwoods and a brown color... [Pg.139]

Analysis. Butenes are best characterized by their property of decolorizing both a solution of bromine in carbon tetrachloride and a cold, dilute, neutral permanganate solution (the Baeyer test). A solution of bromine in carbon tetrachloride is red the dihaUde, like the butenes, are colorless. Decoloration of the bromine solution is rapid. In the Baeyer test, a purple color is replaced by brown manganese oxide (a precipitate) and a colorless diol. These tests apply to all alkenes. [Pg.369]

The coffee plant is a relatively small tree or shmb belonging to the family Rubiaceae. It is often controlled to a height of 3 to 5 meters. Coffea arabica (milds) accounts for 69% of world production Coffea canephora (robustas), 30% and Coffea liberica and others, 1%. Each of these species includes several varieties. After the spring rains the plant produces white flowers. About sis months later the flowers are replaced by fmit approximately the size of a small cherry, hence they are called cherry. The fmit on a tree can include underripe, ripe (red, yellow, and purple color), and overripe cherries. It can be selectively picked (ripe only) or strip picked (predominantly ripe plus some underripe and overripe). [Pg.384]

The purple color end point is not sharp, but as soon as the red hue of the mixture has distinctly changed toward purple, this point is considered reached. A variation of 5-10 cc. either way has little effect, but a large excess gives a large alkali-insoluble residue. [Pg.79]

If the base is filtered off without passing in the excess of hydrogen sulfide, it immediately assumes a purple color on exposure to air. [Pg.94]

Commercially available anhydrous diethyl ether is distilled under nitrogen from a solution of the sodium benzophenone radical anion generated by treating a solution of 10 g of benzophenone and 1 L of ether with 10 g of sodium ribbon until a dark blue or purple color persists. [Pg.79]

The purple color seems to be indicative of a satisfactory reduction. When the color is light or no color develops, the yield is usually poor. Sometimes no reaction occurs. In this instance it is best to discard all residues (pyrophoric) carefully and start over with scrupulous attention to dryness of all apparatus and reagents. [Pg.4]

With potassium ferricyanide and sodium hydroxide solution ephedrine forms benzaldehyde. A solution of the hydrochloride gives with copper sulphate and sodium hydroxide solutions, a purple coloration extractable by ether, leaving the aqueous layer blue. A solution of ephedrine base in chloroform on standing is partially converted into ephedrine hydrochloride. ... [Pg.637]

Although Otsu et al. [12] have studied the BPO-DMA system by electron spin resonance (ESR) technique and trapped the aminomethyl radical, there is still a lack of direct proof of the above second step, particularly concerning the behavior of the aminium radical salt. We [13] have proposed the aminium radical salt with purple color through this reaction of DMT with CCI4 in the presence of O2 following the displacement reaction as ... [Pg.228]

In the ion-exchange technique, separated amino acids exiting (eluting) from the end of the chromatography column mix with a solution of ninhydrin and undergo a rapid reaction that produces an intense purple color. The color is detected by a spectrometer, and a plot of elution time versus spectrometer absorbance is obtained. [Pg.1030]

Because the amount of time required for a given amino acid to elute from a standard column is reproducible, the identities of the amino acids in a peptide can be determined. The amount of each amino acid in the sample is determined by measuring the intensity of the purple color resulting from its reaction with ninhydrin. Figure 26.3 shows the results of amino acid analysis of a standard equimolar mixture of 17 a-amino acids. Typically, amino acid analysis requires about 100 picomoles (2-3 /xg) of sample for a protein containing about 200 residues. [Pg.1030]

Crystals of potassium permanganate falling into water. The purple color of the solution results from absorption at approximately 550 nm. [Pg.18]

As the reaction takes place, the purple color characteristic of Mn04 fades the Fe2+ formed is pale yellow. [Pg.92]

Just past the equivalence point a small excess of Mn04 gives a light purple color to the solution. [Pg.92]

From the color (absorption spectrum) of a complex ion, it is sometimes possible to deduce the value of AOJ the crystal field splitting energy. The situation is particularly simple in 22Ti3+, which contains only one 3d electron. Consider, for example, the Ti(H20)63+ ion, which has an intense purple color. This ion absorbs at 510 nm, in the green region. The... [Pg.420]

Addition of Cl- ions to the yellow complex Co(NH3)63+ converts it to the more stable complex Co(NH3)5Q2+, which has an intense purple color (Table 15.3). [Pg.423]

The purple color of old bottles exposed to the sun for a long time is due to Mn04 ions. These are formed when ultraviolet light oxidizes manganese compounds in the glass. [Pg.549]

As a more complex case, suppose we want to write the equation for the reaction that occurs when hydrogen sulfide gas, H2S, is bubbled into an acidified potassium permanganate solution, KMn04. When we do this, we observe that the purple color of the MnO ion disappears and that the resulting mixture is cloudy (sulfur particles). From Appendix 3 we find the two halfreactions... [Pg.218]

Procedure. To obtain experience in the method, the purity of analytical-grade potassium chlorate may be determined. Prepare a 0.02M potassium chlorate solution. Into a 250 mL conical flask, place 25.0 mL of the potassium chlorate solution, 25.0mL of 0.2M ammonium iron(II) sulphate solution in 2M sulphuric acid and add cautiously 12 mL concentrated sulphuric acid. Heat the mixture to boiling (in order to ensure completion of the reduction), and cool to room temperature by placing the flask in running tap water. Add 20 mL 1 1 water/phosphoric(V) acid, followed by 0.5 mL sodium diphenyl-amine-sulphonate indicator. Titrate the excess Fe2+ ion with standard 0.02M potassium dichromate to a first tinge of purple coloration which remains on stirring. [Pg.378]

The name amethyrin refers to the fact that the dull-purple color of the protonated form of the macrocycle is that of amethyst stones, Formal oxidation or reduction products are the aromatic [22]hexaphyrin(l.0.0.1.0.0) or the [26]hexaphyrin(l.0.0,1.0.0), respectively. However, none of these products could be observed either as reaction products or as direct products of oxidation or reduction reactions. [Pg.708]


See other pages where Purple colorants is mentioned: [Pg.374]    [Pg.374]    [Pg.411]    [Pg.1041]    [Pg.267]    [Pg.337]    [Pg.39]    [Pg.406]    [Pg.418]    [Pg.419]    [Pg.450]    [Pg.401]    [Pg.78]    [Pg.461]    [Pg.43]    [Pg.309]    [Pg.350]    [Pg.161]    [Pg.549]   
See also in sourсe #XX -- [ Pg.168 ]




SEARCH



Color variation purple

Purple

© 2024 chempedia.info