Blueing tints

Tetiasubstituted anthiaquinones give a slightly reddish blue tint to greenish blue color depending on the substituents and their positions, eg, 1,4,5,S-tetraaminoanthraquinone is blue green. 

Chemists also need to know the distribution of electric charge in a molecule, because that distribution affects its physical and chemical properties. To do so, they sometimes use an electrostatic potential surface (an elpot surface), in which the net electric potential is calculated at each point of the density isosurface and depicted by different colors, as in Fig. C.2f. A blue tint at a point indicates that the positive potential at that point due to the positively charged nuclei outweighs the negative potential due to the negatively charged electrons a red tint indicates the opposite. 

Elemental sulfur is a yellow, tasteless, almost odorless, insoluble, nonmetallic molecular solid of crownlike S8 rings (9). The two common crystal forms of sulfur are monoclinic sulfur and rhombic sulfur. The more stable form under normal conditions is rhombic sulfur, which forms beautiful yellow crystals (Fig. 15.12). At low temperatures, sulfur vapor consists mainly of S8 molecules. At temperatures above 720°C, the vapor has a blue tint from the S, molecules that form. The latter are paramagnetic, like O,. 

At the end the cationic indicator (CD) passes into the aqueous phase and a small quantity of the anionic indicator/cationic titrant complex (AD/CT) passes into the organic phase to give a grey/blue tint. 

Redox reactions occur when electrons are transferred between atoms or molecules. Most first-year chemistry students have performed the redox reaction that occurs spontaneously when metallic zinc is placed in a beaker containing an aqueous solution of copper sulfete. A vigorous exothermic reaction ensues and at its conclusion, the zinc has dissolved, the solution has lost its blue tint, and an orange solid has formed. The reaction that occurs is the following ... 

Sadly, this does not mean the planet is like Earth the blue tint probably comes from other gases in the planet s atmosphere. But what if one day scientists find a planet whose reflected light contains the telltale fingerprint of oxygen, as does that of our own... 

The temperature of the mixture must be maintained at 120° or 140° until all the stsrch is redissolved, when it should be suddenly elevated to 167°, as nearly as possible, in order to cause the most powerful action of which the diastase is capable. The thorough agitation of the mixture is then requisite, until the decomposition is almost complete this maybe ascertained liy the deep blue tint which the mixture acquires, and also by the action of iodine, which will communicate to the dextrin a purple or violet tint. 

Green Ultramarine,—Ordinary ultramarine, on ignition with saltpetre, assumes a green color, Green portions, more or less in quantity, are frequently formed in the Crucibles, especially on the first ignition, Od repeated heating it passes into a blue tint. Artificial ultramarine is, however, very rarely entirely freed from all traces of the green modification, and hence it is, for the most part, less beautiful than the natural variety. 

When superheated selenium vapour is passed into air-free water, colloidal solutions are formed which are usually rose-coloured, but at first of a blue tint and cloudy. Under the most favourable conditions clear yellowish-red or deep red sols may be obtained,4 the former being the more highly dispersed. The blue sols after dialysis are extremely stable, but non-dialysed sols decompose after a few days, selenious acid being detected except in the yellowish-red sols. The dialysed sols may be frozen to an almost colourless ice which at the ordinary temperature thaws and decomposes. The sols are negative and are readily coagulated by the addition of chlorides. 

The first observation of fluorescence in solution occurred in 1565 by the Spanish physician and botanist Nicolas Monardes, who noticed a blue tint in the water contained in a recipient fabricated with a specimen of wood called lignum nephriticum [3, 11]. It was known in 1570 that the blue coloration that is produced by white light from the aqueous extract of the lignum nephriticum or peregrinum disappeared in acid medium. In 1615 a similar behavior was observed from the rind of Aesculos hippocastanum in aqueous medium [4]. When placed in water, the rind of chestnut produces a colorless liquid with bluish reflections today it is known that this originates from aesculin fluorescence [12]. 

At present, only blue dioxazines are used commercially to color cellulose, where R is varied to give reddish to greenish-blue tints. Variation of T has only a minor effect on the shade. 

Prof. Dr. Jan Markiewicz, Jan Sehn Institute for Forensic Research, Toxicology Department, Cracow, on behalf of the Auschwitz State Museum. J. Markiewicz provides more exact data on the sample taking locations, the type of material, and the depth taken in a sample taking records. The control samples were taken from a disinfestation chamber in the Auschwitz main camp, the interior walls of which, according to the report, were painted during the war, so that only a pale blue tint is visible in places. This is not, therefore, unaltered masonry material thus, in case the samples were taken from the upper layer of the wall only, one has to expect lower results in comparison to an untreated wall.56,57... 

Bailer s argument does not explain the only pale blue tint of the interior south walls of the original disinfestation wing of Building 5a. 

The GC analysis data show samples of German chamomile, Matricaria recutica, with a presence of chamazulene at 3.27% (Fig 7.10). Typical values would be in the range of 2.5-7.5%. Analysis of the Roman/English, Anthemis nobilis (Fig. 7.11), does not show any chamazulene as it is below the level (0.01%) that would be detected by the GC analysis. However, the oil itself may show a pale blue tint due to traces of chamazulene. 

Reactions of Salts of Ruthenium.—A delicate and characteristic reaction of ruthenium chloride consists in formation of an azure-blue tint (possibly due to the formation of dichloride) when hydrogen sulphide is passed through its solution in water. 

Cadmium hydroxide forms a red-coloured lake with the reagent, which contrasts with the blue tint of the latter. 

Cuprous cyanide is a white solid, and is soluble with difficulty in water. It is dissolved readily by cold, concentrated hydrochloric acid, and is reprecipitated from this solvent by addition of an aqueous solution of potassium hydroxide. In contact with air, its colourless solution in ammonium hydroxide develops a blue tint. The salt is also dissolved by aqueous solutions of ammonium chloride, sulphate, and nitrate, and by warm, dilute sulphuric acid. None of its solutions has the power of absorbing carbon monoxide.13 The heat of formation of... 

The leuco compound (7.9 grams, 0.01 mole) is dissolved in 100 cc. 50 per cent acetic acid, and to the well stirred solution are added, simultaneously, 30 cc. 10 per cent oxalic acid solution and 12.5 cc. 10 per cent sodium bichromate solution. The mixture turns blue immediately and the oxidation is complete in 10 minutes. The solution is mixed with an equal volume of saturated salt solution and the acetic acid is neutralized with ammonia. The dye precipitates as a reddish, bronzy slime which soon becomes glass-hard. The product is dissolved in hot water, the solution is filtered, and the dye is then salted out by adding an equal volume of saturated salt solution. In this way, 7.8 grams of pure dye is obtained. It gives bright blue tints on wool from neutral or weakly acid solution. The dye is not very fast to light. 

Toluene Green with blue tint Color unchanged 3 ... 

Figure 10-1. Reflectance of a bleached cotton fabric (A), after adding a blue tint (B) and after adding a fluorescent brightener (C) [1].

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