Violet black

Ozone s presence in the atmosphere (amounting to the equivalent of a layer 3 mm thick under ordinary pressures and temperatures) helps prevent harmful ultraviolet rays of the sun from reaching the earth s surface. Pollutants in the atmosphere may have a detrimental effect on this ozone layer. Ozone is toxic and exposure should not exceed 0.2 mg/m (8-hour time-weighted average - 40-hour work week). Undiluted ozone has a bluish color. Liquid ozone is bluish black and solid ozone is violet-black. 

Violettschwarz, n. violet black, violettstichig, a. violet-tinged, virginisch, a. Virginian. 

Dithizone is a violet-black solid which is insoluble in water, soluble in dilute ammonia solution, and also soluble in chloroform and in carbon tetrachloride to yield green solutions. It is an excellent reagent for the determination of small (microgram) quantities of many metals, and can be made selective for certain metals by resorting to one or more of the following devices. 

Fig. 8.6 Conversion of a violet-black to a yellow Ni(III) species, Ni(H AlaAla)2 monitored by epr and showing isosbestic points. There is 0.35 s between scans which are run in 0.125 M and at 25 C.

Violet-black solid density Id.Og/cm decomposes on heating at 550°C insoluble in water and alcohol soluble in aqua regia. 

CH2)2L0) were prepared. - " Such compounds can be oxidized with lead dioxide to N-picryl-9-aminocarbazyls (133). These black species are dehydrogenating agents though stable in dry chloroform the transformation of violet-black color into orange in benzene solution suggests that they... 

Thallous halides do not absorb ammonia at ordinary temperature, but in liquid ammonia these salts form triannnino-thallous halides of composition [T1(NH3)3]C1, [Tl(NH3)3]Br.1 The triammino-deriva-tives formed are somewhat soluble in liquid ammonia, and the solubility increases with rise of temperature and increase in atomic weight of the halogens. No lower ammino-derivatives are known. Tliallic halides absorb ammonia gas readily. If ammonia gas is passed into an alcoholic solution of thallic chloride, or if dry ammonia gas is passed over dry thallic chloride, the gas is absorbed and a white crystalline substance is formed of composition [T1(NH3)3]C13. The crystals may be washed with alcohol containing ammonia and then with absolute alcohol, and finally dried in vacuo. On coming in contact with water the triammine is decomposed with precipitation of violet-black oxide thus ... 

Iodine is a violet-black crystalline substance. Iodine vapour irritates the respiratory tracts and the mucous membrane. If poisoned by iodine vapour, inhale vapour of a 2% aqueous solution of ammonia. 

The unstable, violet black compound (NH4)2[Cr2I02(02)5] 2H20 is produced1435 by reaction of H202 with Cr03 in the presence of NH4C1 and HC1, and Cr(02)(NPr2)3 may be a peroxo chromium(V) compound (p. 138). 

Isatin chloride and 3-hydroxyselenonaphthene are. mixed in benzene and the solution boiled, when the required compound separates as a violet precipitate. It dissolves sparingly in xylene with a red-violet fluorescence and deposition of violet-black needles, M.pt. 335° C. In concentrated or fuming sulphuric acid and chlorosulphonic acid it gives intense blue solutions, forming a water-soluble red-violet fluorescent sulphonic acid, which yields pale yellow alkali salts. 

Elemental iodine, I2 (solid, sublimes at 184°C), consists of violet-black rhombic crystals with a lustrous metallic appearance. More irritating to the lungs than bromine or chlorine, its general effects are similar to the effects of these elements. Exposure to iodine is limited by its low vapor pressure, compared to liquid bromine or gaseous chlorine or fluorine. 

The corresponding reactions in the benzoquinone field were discovered by Cameron and Giles128 in 1965, who reported rapid decoloration of the violet-black quinones (242) on exposure to sunlight. The product was the benzoxazoline (243) which with acid treatment followed by oxidation, gave the quinone (245).129 A second irradiation process yielded the bis(monomethylamino)benzoquinone (246). Analogous benzoxazolines (248) were isolated from the pyrroli-dino-, the piperidino-, and the perhydroazepinobenzoquinones (247). 

On cooling liquid ozone in liquid hydrogen, it solidifies m violet-black crystals, melting at —249-7° C. Its critical temperature is — 5° C. critical density 0-587 critical pressure 64-8 atmospheres. Its density at the boiling-point is 1-46.7... 

When the reaction has subsided, nitric and sulphuric acids are added, whereby barium sulphate is precipitated. The clear solution is decanted and distilled until one-quarter of its volume has been collected as distillate. This latter liquor is rich in osmium and may be worked for that metal (see p. 208). The residue is evaporated to small bulk. Ammonium chloride and a small quantity of nitric acid are added, and the mixture evaporated to dryness on the water-bath. A violet-black crystalline solid is obtained which is washed with water half saturated with ammonium chloride until the filtrate is colourless. The insoluble residue consists of fairly pure ammonium chlor-iridate containing ruthenium, from which the spongy metals are obtained by ignition. 

It is noteworthy that the color of compounds 70a to c, which is yellow for all of them in solution, changes from transparent orange for the weakest donor (Ar = C6H5) to violet-black for the better donors (e.g., Ar = C6H4OCH3) in the solid state. This solid-state phenomenon shows that there is indeed an influence of the substituents on the donor entities, which changes the energy gap AE between the neutral ground state and the excited ionic state in subtle ways. 

Colour Tests. Ferric Chloride—blue Liebermann s Test— black Marquis Test—violet- black Methanolic Potassium Hydroxide—green- red Kessler s Reagent—black. 

Colour Test. Ferric Chloride—violet-black- blue-black. Ultraviolet Spectrum. Methanol—275 nm (A = 540 b). 

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