Black colour

C7H6O5. Colourless crystals with one molecule of water, m.p. 253" C, sparingly soluble in water and alcohol. It occurs free in woody tissue, in gall-nuts and in tea, and is a constituent of the tannins, from which it can be obtained by fermentation or by acid hydrolysis. It gives a blue-black colour with Fe and is used in the manufacture 6f inks. On heating it gives pyrogallol. 

In contrast to the reaction with lithium amide, the sodium amide suspension immediately settles out after stopping the stirring and the supernatant ammonia has a grey or black colour, due to colloidal iron. In some cases it took a long time before all of the sodium had been converted (note 4). A further 0.1 g of iron(III) nitrate was then added to accelerate the reaction and some liquid ammonia was introduced to compensate for the losses due to evaporation. 

The bitumens have a good order of chemical corrosion resistance, have reasonably good electrical insulation properties and are very cheap. Their main disadvantages are their black colour and their somewhat brittle nature. 

Fillers. They are generally added to reinforce NBR adhesives. However, fillers can be added to promote tack, to increase the storage life, to improve heat resistance or to reduce cost. The most common fillers are carbon blacks. Precipitated silica can be used in applications where black colour is not acceptable, but excessive amounts tend to reduce adhesion. Titanium dioxide can be used to impart whiteness, improves tack and extend storage life. 

Pure Commercial Benzene, obtained from coal-tai naphtha, should distil w lthin one degiee (80—Si ), and solidify completely when cooled to 0°. Other tests are as follow s shaken with concentrated sulphuric acid for a few minutes, the acid should not darken, and a drop of bromine water should not be immediately decolourised. A single distillation over a few small pieces of sodium, which absorb any traces of water, is usually a sufficient purification. If the benzene impart a brown or black colour to the sulphuric acid, it must be repeatedly shaken with about 20 per cent, of the acid until the lattev becomes only slightly yellow on standing. This is done in a stoppered separating funnel, and after shaking fora few minutes the mixture is allow ed to settle, and the low er layer of acid diawn off. The benzene is then shaken tw o 01 three times with water to free it from acid, carefully separated from the aqueous layer, and left in contact with fused calcium chloride until the liquid becomes clear. It is then decanted, frozen in ice, and any liquid (carbon bisulphide, paraffins) carefully drained off, and die benzene finally distilled over sodium. 

Figure 3 displays a Band Ratio image (5/3, 7/3, 4/2), in which peridotite appears dark yellowish black colour. It is difficult to distinguish between gabbro and basalt, due to their similar reflectance properties. 

Xanthene dyes are used as colour formers. These so-called fluorans usually contain amino groups sited para and meta to the central carbon atom. Such a substitution pattern gives rise to broad absorption bands and leads to almost black colour production the lactone 6.200 is a typical example. This xanthene derivative finds use in direct thermal printing [36]. The chemistry of fluoran leuco dyes has been reviewed [78]. 

Iron sulphides are ubiquitous in marine and freshwater sediments. They are usually present either as pyrite or as monosulphides, which can be liberated by hydrochloric acid. These acid volatile sulphides give rise to an intense black colour that is characteristic of anoxic sediments. They play an important role in recent diagenetic processes in sediments and the ratio of pyrite to acid volatile sulphides has been used as an historical indicator to determine whether sediments were formed in marine or freshwater conditions. They can be present over a wide range of... 

UV stabilizers or/and black colour are needed Good behaviour... 

Fig. 2. SEM-BSE image and EPMA maps from Esfordi deposit, a) White crystals in fractures are REE minerals, b). RE minerals (sketched by black colour) are interstitial to actinolite (gray parts), c) RE minerals (black) and apatite (white) EPMA map.

C. If a blue or blue-black colour appears in receiver 6 (explain its origin), lower the evaporation temperature of the carbon tetrachloride to 50 °C. Perform chlorination during 15 minutes. 

The existence of a black form of sulphur was first suggested by Mitscherlich in 1856, who observed that in the presence of very slight traces of organic impurities, plastic sulphur could be obtained with a very deep or even black colour 8 the necessity for the presence of... 

One of the earliest references to a reaction in solution, which, as we now realize, depends upon the formation of a coordination compound, was recorded by Pliny who stated that the adulteration of copper sulfate by iron sulfate could be detected by testing with a strip of papyrus soaked in gall-nuts, when a black colour developed if iron were present. A. Libavius (1540-1616) noted how ammmonia present in water could be detected by the blue colour formed with a copper salt and A. Jacquelain (1846) actually determined copper salts in terms of the blue colour formed on adding ammonia. Later developments used coordination compounds formed from ethylenediamine and other polyamines.3 T. J. Herapath determined iron(III) as its red isothiocyanate complex in 1852 and the basic procedure is used today.3... 

The jet black colour is produced by the admixture of the finely divided mercury with the white precipitate. With aq. ammonia both hydrolysis and ammonolysis may occur, thus, with mercuric chloride ... 

Figure 15.20 A dark blue-black colour is produced when dilute iodine solution is applied to starch, for example in a potato.

Test for phosphorus. The presence of phosphorus may be indicated by a smell of phosphine during the sodium fusion and the immediate production of a jet-black colour when a piece of filter paper moistened with silver nitrate solution is placed over the mouth of the ignition tube after the sample has been dropped on the hot sodium. Treat 1.0ml of the fusion solution with 3ml of concentrated nitric acid and boil for 1 minute. Cool and add an equal volume of ammonium molybdate reagent (3). Warm the mixture to 40-50 °C, and allow to stand. If phosphorus is present, a yellow crystalline precipitate of ammonium 12-molybdophosphate, (NH4)3[PMo12C>4o], will separate. 

In those climatic regions where humus is developed, it is normally found in undisturbed forested areas above the normal mineral soil. Decomposed black coloured organic material (humus) should be sampled. 

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