Deep blue color

Ltebermann Reaction To 1 minute crystal of sodium nitrite in a clean dry test-tube add 0 5 g. of phenol and heat very gently for about 20 seconds allow to cool and add twice the volume of cone. H2S04. On rotating the tube slowly in order to mix the contents, a deep green or deep blue coloration develops (some times only after i 2 minutes). Dilute cautiously with water the solution turns red. Now add an excess of NaOH solution the green or blue coloration reappears. 

Iodine compounds are important in organic chemistry and very useful in medicine. Iodides, and thyroxine which contains iodine, are used internally in medicine, and as a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. The deep blue color with starch solution is characteristic of the free element. 

Iron, cobalt, and nickel catalyze this reaction. The rate depends on temperature and sodium concentration. At —33.5°C, 0.251 kg sodium is soluble in 1 kg ammonia. Concentrated solutions of sodium in ammonia separate into two Hquid phases when cooled below the consolute temperature of —41.6°C. The compositions of the phases depend on the temperature. At the peak of the conjugate solutions curve, the composition is 4.15 atom % sodium. The density decreases with increasing concentration of sodium. Thus, in the two-phase region the dilute bottom phase, low in sodium concentration, has a deep-blue color the light top phase, high in sodium concentration, has a metallic bronze appearance (9—13). 

When hydrogen peroxide is added to an acid solution of Cr(VI), a deep blue color, iadicating the formation of chromium (VI) oxide diperoxide [35262-77-2] is observed. This compound is metastable and rapidly decomposes to Cr(III) and oxygen at room temperature. The reaction... 

If the solution is acidified and aUtde ferric sulfate added, ferric ferrocyanide [14038-43-8], Fe4[Fe(CN)g]2, is produced. This salt has a characteristic deep blue color, and the reaction may be used to test for the cyanide. 

While keeping the collected deuterioammonia at dry ice-isopropyl alcohol temperature, lithium wire (10 mg) is added, followed by a solution of 3/3-hydroxy-5a-cholest-7-en-6-one (161 50 mg) in anhydrous tetrahydrofuran (4 ml). The reaction mixture is stirred for 20 min, the cooling bath is then removed and the ammonia is allowed to boil under reflux for 40 min. A saturated solution of ammonium chloride in tetrahydrofuran is added dropwise until the deep blue color disappears and then the ammonia is allowed to evaporate. The residue is extracted with ether and the organic layer washed with dilute hydrochloric acid and sodium bicarbonate solution and then with water. Drying and evaporation of the solvent gives a semicrystalline residue which is dissolved in acetone and oxidized with 8 N chromic acid solution. After the usual workup the residue is dissolved in methanol containing sodium hydroxide (0.2 g) and heated under reflux for 1 hr to remove any deuterium introduced at C-5 or C-7. (For workup, see section II-B). 

Sylvestrene yields the following characteristic reaction. If a drop of concentrated sulphuric acid be added to a solution of one drop of sylvestrene in acetic anhydride, a deep blue coloration results. No other terpene appears to give this reaction. 

Sapphyrins were discovered serendipitously by Woodward33 during the course of synthetic studies directed towards the total synthesis of vitamin B, 2. The sapphyrins were the first example of expanded porphyrins in the literature. Due to sapphyrin exhibiting a deep-blue color in the crystalline state and intense green in solution. Woodward coined the expression sapphyrin with reference to the deep-blue color of sapphire stones. 

This yields colorless to slightly yellow chromatogram zones on a deep blue-colored background. 

Dioxane was heated at reflux with sodium overnight under nitrogen, benzophenone was added, and the solvent was distilled after appearance of the deep blue color of the benzophenone ketyl. 

Blue copper proteins. A typical blue copper redox protein contains a single copper atom in a distorted tetrahedral environment. Copper performs the redox function of the protein by cycling between Cu and Cu. Usually the metal binds to two N atoms and two S atoms through a methionine, a cysteine, and two histidines. An example is plastocyanin, shown in Figure 20-29Z>. As their name implies, these molecules have a beautiful deep blue color that is attributed to photon-induced charge transfer from the sulfur atom of cysteine to the copper cation center. 

The hydrolysis reaction is very slow at ambient temperatures and is accelerated by boiling chromium salt solutions (5). The hydrolysis reaction is characterized by the transformation of the deep blue colored CrtHgOJg to green colored hydrolyzed olates. Another indication is tnatan aged or boiled Cr(III) salt solution has a higher neutralization equivalent than a fresh one due to the hydrolytically produced protons. One way to establish hydrolytic equilibria quickly is to add appropriate equivalents of bases such as NaOH to Cr(III) salt solutions. 

In both research and practice, critical localised concentrations of metal contamination can be difficult to detect. Potassium hexacyanoferrate(II) (10.80) gives an intense deep blue coloration with iron(III), permitting extremely sensitive detection of tiny iron spots even by visual inspection. It is recommended as a quality control measure on batches of cotton destined for bleaching [237]. However, in view of the random distribution of metal traces, even the most sensitive test cannot guarantee freedom from contamination throughout a batch of goods to be bleached. 

Whether for a class demonstration, a practical joke, or perhaps a clandestine activity, disappearing ink is a fascinating substance. What is the secret to its action One formulation of disappearing ink contains a common acid-base indicator, that is, a substance that by its color shows the acid or basic nature of a solution. One acid-base indicator that shifts from a colorless hue under acidic conditions to a deep blue color in alkaline solutions is thymolphthalein. If the indicator starts off in a basic solution, perhaps containing sodium hydroxide, the typical blue color of an ink is perceived. How does the ink color disappear This behavior is dependent upon the contact of the ink with air. Over time, carbon dioxide in the air combines with the sodium hydroxide in the ink solution to form a less basic substance, sodium carbonate. The carbon dioxide also combines with water in the ink to form carbonic acid. The indicator solution responds to the production of acid and returns to its colorless acid form. A white residue (sodium carbonate) remains as the ink dries. 

Disappearing ink can be prepared by first dissolving solid thymolphthalein in ethanol, adding water, and then adjusting the pH with sodium hydroxide solution J2 The deep blue color of the basic form of the indicator is readily apparent. Applying the ink to paper increases its exposure to carbon dioxide in air. Two chemical... 

Fakhr Eldin et al. [22] described a simple sequential spectrophotometric method for the assay of penicillamine. The method is based on the complex formed when the drug is reacted with Fe(III) solution in hydrochloric acid media. The deep blue colored drug Fe(III) complex is monitored at a maximum wavelength of 600 nm. 

Sufficient sodium and benzophenone are used to produce a permanent deep blue color when the solution is refluxed under nitrogen e.g., for 400 ml. of crude n-propyl ether, 10 g. of benzophenone and 15 g. of sodium are usually sufficient. The ether is then distilled under a nitrogen atmosphere. 

Conversion is indicated by discharge of the deep blue color. 

The dication 212+ exhibited a reduction wave upon CV at a less negative potential than that of 3b+. This wave corresponds to a one-step, two-electron reduction of 212+. In the electronic spectra, dication 212+ also showed strong absorption in the visible region. The extinction coefficients for the dication was almost twice as large as those of monocations. The deep-blue color of the... 

When the solutions begin to boil, remove them from the hot plate and add the NH4OH from the squeeze bottle with continuous stirring until the solutions become quite murky with the Fe(OH)3 precipitate and the precipitate settles readily upon standing. Now test the solution with litmus paper (be sure to rinse the paper back into the beaker). If the paper does not turn a deep blue color, add more NH4OH until it does. Be careful not to add too much. If the solution becomes too basic, other metals will precipitate, causing an error. 

This ion gives a deep blue color when excess aqueous ammonia is added to a solution containing it. 

The DPA test is another common spot test for nitrate esters and nitramines [1, 3, 4, 50-55]. The reagent (1% DPA in concentrated sulfuric acid) is oxidized in the presence of these explosives, producing a deep blue color. 

---