Blue-green colour

Secondary nitro compound dark blue or blue green colour due to nitro-iiitroso derivatives. The coloured compound is soluble in chloroform. 

CopperQ bromide, Limonene Wilson, C. W. et al., J. Agric. Food Chem., 1975, 23, 636 Addition of all the perester in one portion to limonene and catalytic amounts of copperQ bromide before oxidation had begun, as shown by development of a blue-green colour, led to an explosion. 

The word root cyan in cyanophyte means a blue-green colour, rather than cyanide. 

In other words, the small excess of HN02 present at the end-point can be detected visually by employing either starch-iodide paper or paste as an external indicator. Thus, the liberated iodine reacts with starch to form a blue green colour which is a very sensitive reaction. Besides, the end-point may also be accomplished electrometrically by adopting the dead-stop end-point technique, using a pair of platinum electrodes immersed in the titration liquid. 

Solutions of many organic nitroso compounds, R—NO, display blue or blue-green colours owing to a weak absorption in the visible region (X 700 nm, e < 50). In the crystalline state, however, most of these compounds are colourless or at most pale yellow. The reason for this phenomenon is the dimerization reaction124. The dimers have an NN distance of about 131 pm, which indicates a certain degree of double-bond character, and show E/Z isomerism. They may thus be termed diazene-1,2-dioxides. 

Phthalocyanines are actually of great applicative interest (because of their intense blue-green colour they are used in dyes, pigments and paints, and colour photography) and up to now have been studied much more than porphyrazines. 

After absorption of the blue-green colour from white light (carotene absorbs light of wavelength up to about 500 nm), the complementary colour (red-yellow) remains to be reflected and perceived by our eyes. P-Carotene, therefore, appears intensely orange coloured as the name implies, it is found in high concentrations in carrots. 

Aerial oxidation often leads to the formation of the blue-green colour at this stage. 

Malachite green Alkaline medium, Ce4+ gives blue green colour 3 [57]... 

Malachite green Pr60n in acetate solution gives blue green colour 0.3 [62]... 

Add 1 drop of the methyl violet indicator solution and introduce dilute HC1 or dilute aqueous NH3 (as necessary) dropwise and with constant stirring until the colour of the solution is yellow-green a blue-green colour is almost but not quite acid enough, yet is acceptable for most analyses. (If the indicator paper is available, the thoroughly stirred solution should be spotted on fresh portions of the paper.) It is recommended that a comparison solution containing, say, 10 ml... 

E20.22 The blue-green colour of the Cr ions in [Cr(H20) ] is caused by spin-allowed but Laporte-forbidden ligand field transitions. The relatively low-molar-absorption coefficient, , which is a manifestation of the Laporte-forbidden nature of the transitions, is the reason that the intensity of the colour is weak. The oxidation state of chromium in tetrahedral chromate dianion is CifVI), which is d . Therefore, no ligand field transitions are possible. Ilte intense yellow colour is due to LMCT transitions (i.e., electron transfer from the oxide ion ligands to the Cr(VI) metal centre). Charge transfer transitions are intense because they are both spin-allowed and Laporte-allowed. 

Detection of proazulene (Malricariae flos) After heating at 100 C for 5-10 min, proazulene gives a blue-green colour (vi.s.) The blue colour of azulene is inten.sified by EP reagent. 

Even smaller than the handheld devices above is a newly developed pen-like device which can detect sub-milligramme amounts of peroxide-based explosives . The prototype costs less than 23 per unit. A suspect sample is placed on a silicone rubber test pad. Three test chemicals are sequentially injected into the transparent chamber in the pen and a blue-green colour change occurs on reaction with any peroxide present in the sample within three seconds. 

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