Blacks forms

Several aHotropes of black phosphoms have also been reported (2). These include one amorphous and three crystalline modifications. At increasing pressures and temperatures reaching above 1200 MPa (12 kbar) and several hundred degrees, a series of black phosphoms modifications are formed that are characterized by even higher densities (2.70 g/cm ). These include orthorhombic, rhombohedral, and cubic varieties. The black forms have lower reactivity and solubiUty than red phosphoms. 

Arsenic exists as grey, yellow and black forms of differing physical properties and susceptibilities towards atmospheric oxygen. The general chemistry is similar to that of phosphorus but whereas phosphorus is non-metallic, the common form of arsenic is metallic. Traces of arsenides may be present in metallic residues and drosses these may yield highly toxic arsine, ASH3, with water. 

Most black pigments are made of carbon black formed by depositing carbon from a smoky flame of natural gas on a metal surface. Lampblack is made similarly by burning oik Bone blacks are made from charred bones. Graphite occurs naturally or can be prepared from coal in electric furnaces. Mineral blacks come from shale, peat, and coal dust. Iron oxide blacks are found in nature or prepared. Blue lead sulfate is a pigment for priming. Of these, carbon black is su[XTinr. 

No TI2S3 known] TIS2 Tl polysulfide TI2S5 (red and black forms) Tl Tl2Se3 (Tl2Te3)... 

Ring fusion seems to occur in the quinoxaline derivative (28), which has been stated to exist in red and blue-black forms. Other derivatives of type 28 are reported. Attempts to prepare 5,6-furo-xanobenzofuroxan by pyrolysis of the azide (29) met with no success. An early example in the literature of such a linear fused structure was shortly afterward revised to the angularly fused type (17). 

A form of rust. Magnetic, dark-gray-to-black form of iron oxide (Fe304) that forms a protective film on steel surfaces. 

The most thermod3Tiamically stable form of the element is black phosphorus, which can be prepared by heating red phosphorus under high pressure. The black form contains chains of P4 units cross-linked by P—P bonds, making this form even more polymerized and less strained than red phosphoms. Example explores another difference between the elemental forms of phosphorus. 

It is a pyrophoric and treacherously shock-sensitive explosive, especially as the dry black form. It will deflagrate under nitrogen or argon when scratched with a spatula, and ignites in contact with poly(chlorotrifluoroethylene), (Fluorolube). The caesium and rubidium salts are not shock-sensitive but will deflagrate on friction and are... 

However, the reduction reactions in which a solid reducing agent is used usually give impure products. In this case, the product contains 80% to 95% boron that also contains magnesium and boron oxide as impurities. The boron produced in this way is a brownish-black form having a density of 2.37 g/cm3. 

Several allotropic forms of phosphorus are known, the most common of which are the white, red, and black forms. Heating the white form at 400 °C for several hours produces red phosphorus, which is known to include several forms. A red form that is amorphous can be prepared by subjecting white phosphorus to ultraviolet radiation. In the thermal process, several substances (I2, S8, and Na) are known to catalyze the conversion of phosphorus to other forms. Black phosphorus consists of four identifiable forms that result when white phosphorus is subjected to heat and pressure. Phosphorus is used in large quantities in the production of phosphoric acid and other chemicals. White phosphorus has been used extensively in making incendiary devices, and red phosphorus is used in making matches. 

Antimony in its black form (Stibnite, Sb S ) was known at least 4,000 to 5,000 years ago. Egyptian women used it as an eyeliner for both themselves and their children. It was known during biblical times and was referred to as stick-stone it was also used during this time as black eyeliner for wealthy women. 

The number of free radicals detected by EPR in porous carbons varies from 10 to 10 radicals per gram and is strongly dependent on the per cent carbon content of the carbon. Likewise in the carbonization of organic materials the number of radicals is strongly dependent on the temperature of carbonization a maximum number of radicals is attained by carbonization between 500 and 600°. Heat treatment of carbon blacks formed by pyrolysis of natural gas and oils also results in a variation 182) of the number of unpaired electrons. 

CARBON, DECOLORIZING. (Activated carbon, bone black.) Forms of carbon having large surface area so that it has capacity to remove colors and impurities from air, gas, or solution. 

Green cubic crystals transforms to a grayish black octahedral form, known as black oxide, when strongly ignited black oxide has a metallic luster density of green oxide is 6.72 g/cm Mohs hardness 5.5 melts at 1955°C insoluble in water soluble in acids at ordinary temperatures black form dissolves in hot acids. 

Several nickel salts are obtained by reactions of nickel oxide with mineral acids. Thus, the reaction of black nickel oxide with hot dilute sulfuric acid forms nickel sulfate, NiS04 6H2O. Similarly, dilute nitric acid, hydrochloric, and hydrobromic acids when heated react with the black form of nickel oxide to yield corresponding nickel salts as hexahydrates. 

Amorphous forms exhibit two colors, occurring as a red powder of density 4.26g/cm3 that has a hexagonal crystal structure and a black vitreous solid of density 4.28g/cm3. The red amorphous selenium converts to the black form on standing. Amorphous selenium melts at 60 to 80°C insoluble in water reacts with water at 50°C when freshly precipitated soluble in sulfuric acid, benzene and carbon disulfide. 

The flow behaviour of polymeric electrophotographic toner systems containing carbon black varying in surface area and concentration were determined using a cone and plate rheometer [51]. As the concentration of carbon black was increased, the viscosity at low shear rates become unbounded below a critical shear stress. The magnitude of this yield stress depended primarily on the concentration and surface area of the carbon black flller and was independent of the polymer (polystyrene and polybutyl methacrylate) and temperature. It was postulated that at low shear rates the carbon black formed an independent network within the polymer which prevented flow. 

Thermal black Soft carbon black formed by the decomposition of natural gas (e.g., MT, medium thermal black). It has little stiffening effect, but imparts toughness, resilience, good resistance to tearing, and fair abrasion resistance. 

Perchlorate C black form a solid rocket fuel Refs 1) Beil, not found 2) W.A. Gey R. Reed Jr, USP 3121748(1964) CA 60, 11897g (1964)... 

It is obtained by adding oxygen to Sb hydride at -90°. It is unstable and changes to the black form at temps above -90°. According to Krebs et al (Addnl Ref C), the yel form is a mixed polymer contg chemically bonded H atoms... 

The blackt amorphous, form is produced by sudden cooling of Sb vapors. The black form is more active and more easily volatilized than the metallic form. It is said (Ref 5, p 51), that if Sb is distilled in high vacuum, it deposits as an amorphous powder which might explode on heating or scratching... 

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... 

Extraction.—(1) From Pyrites.—In the oxidation of the pyrites (or other sulphur mineral) for the formation of sulphur dioxide in the manufacture of sulphuric acid, foreign elements like arsenic and selenium also undergo oxidation and pass ofC as vapours with the sulphur dioxide. The selenium dioxide produced in this manner their suffers more or less complete reduction by the sulphur dioxide, when finely divided selenium separates, mainly in the lead chambers, as a red, amorphous powder, accompanied possibly by some of the greyish-black form a portion of the dioxide is also found in the Glover tower acid. The amount of selenium in the chamber mud depends, of course, on the nature of the pyrites relatively large quantities of compounds of arsenic, zinc, tin, lead, iron, copper or mercury are always present, arising almost entirely from impurities in the pyrites. 

A gas black apparatus consists of a burner pipe approximately 5 m long, which carries 30-50 diffusion burners. The flames burn in contact with a water-cooled drum, where about half of the carbon black formed is deposited. This black is scraped off and transported by a screw to a pneumatic conveying system. The gas black apparatus is surrounded by a steel box open at the bottom. At the top of it, fans suck the off-gas into filters, which collect the carbon black suspended in the gas. 

Phosphorus with four forms, two white forms, a violet, and a black form. Red phosphorus is a mixture of the white and violet forms. 

Lead nithopluiuhaie, Pb-PbOj, ted lead, is similarly described ns a sail, in Ihi.s ease an orihoplumbalc of divalent lead. Pb PbO i. because on treatment with nitric acid, two-thirds of the lead dissolves and one third remains us PbO . It is prepared in the red farm by atmospheric heating of PbO. and in a black form by reaction nl" pbO with pure oxygen. Red lead is formed of PhOj, octahedra (with one common edge I linked by lead atoms covalently bonded to three oxygen atoms. 

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