Black compounds

Mixed oxides of Fe(IV) can be prepared by heating iron(III) oxide with a metal oxide or hydroxide in oxygen at elevated temperatures. These black compounds have general formulas M FeO, M monovalent, or M2Fe04, M divalent, but do not contain discrete [FeOJ" ions. They are readily decomposed by mineral acids to iron(III) and oxygen. 

Carbon blacks are usually used as fillers. The semi-reinforcing types, such as PEP (Past Extmsion Pumace) and SRE (Semi-Reinforcing Pumace) give the best performance (see Carbon, carbonblack). To lower the cost and improve the processibiUty of light compounds, or to lower the cost of black compounds, calcined clay or fine-particle calcium carbonate are used. 

For equivalent particle size the carbon blacks are the most powerful reinforcing fillers. However, fine particle size silicas can be very useful in non-black compounds whilst other fillers such as aluminium hydroxide, zinc oxide and calcium silicate have some reinforcing effect. 

MesSiNs yields (SN)x as a black solid. By contrast, the explosive and insoluble black compound SesNaCla, which probably contains the [SesNaCl]" cation, is prepared by the treatment of SeaCla with trimethylsilyl azide in CH2CI2 (Eq. 2.13). ... 

The black compound I7SO3F (mp 90.5°) was established as a local mp maximum in the phase diagram of the system I2/S2O6F2, together with the known compounds I3SO3F (mp 101.5°), ISO3F (mp 50.2°), and I(S03F)3 (mp 33.7°), but its structure has not been determined and there is at present no evidence for the presence of the discrete heptaatomic cation I7+ in the crystals. 

Molecules of the deep blue-black compound AuI3(PMe3)2 have a trigonal bipyramidal structure in which Au-P is 2.333-2.347 A and Au-I is 2.709-2.761 A. It is prepared by the reaction of gold metal with Me3PI2 [138b]... 

Salmonella typhi, in the presence of glucose, reduces bismuth sulphite to bismuth sulphide, a black compound the organism can produce hydrogen sulphide from sulphur-containing amino acids in the medium and this will react with ferrous ions to give a black deposit of ferrous sulphide (Table 1.2). 

Zinc oxides can be prepared from chemical industry by-product sources and from zinc soaps from a variety of industrial processes. These grades are generally off-coloured and consequently considered of lower grade and offered at lower cost and are confined to use in black compounds. These grades can also vary in consistency, batch to batch, causing cure variation in compounds containing them. 

Melanin from natural sources falls into two general classes. The first component is pheomelanin (I), which has a yellow-to-reddish brown colour, and is found in red feathers and red hair. The other component is eumelanin (which has two principal components, II and III). Eumelanin is a dark brown-black compound, and is found in skin, hair, eyes, and some internal membranes, and in the feathers of birds and scales of fish. Melanin is particularly conspicuous in the black dermal melanocytes (pigment cells) of dark-skinned peoples and in dark hair and is conspicuous in the freckles, and moles of people with lighter skins. 

The reaction between Ni2Cp2(C2R2) and Fe3(CO)i2 in refluxing benzene produces a series of black compounds formulated as Fe2Ni2(CO)6Cp2(C2R2)... 

A technique of developing Aniline Black directly on the fiber was found by Lightfoot in the period between 1860 and 1863. In accordance with this process, the fiber is soaked with aniline, aniline hydrochloride, and sodium chlorate in the presence of an oxidation catalyst (e.g., ammonium vanadate, potassium hexa-cyanoferrate(II)). The compound is developed at 60 to 100°C and then oxidized further with sodium chromate. It should be noted, however, that Perkin had already synthesized a black compound which he called Aniline Black as early as 1856. He oxidized aniline (containing toluidine) with potassium dichromate and separated Aniline Violet from the resulting black mixture (Aniline Black). 

The Other additives in the compound can also influence weathering as we can see in Table 3.14, which displays the effect of colorants in combination with UV stabilization. Ageing behaviour depends on the nature of the colorant and the UV-filtering action of the filler. Black compound is by far the best choice. 

Polysulfones are inherently UV sensitive and must be protected by addition of anti-UV and other protective agents. Black compounds are generally more resistant. 

Polyphenylene sulfides are inherently resistant to UV, weathering and hydrolysis. Black compounds are the most UV-resistant. 

Copper and copper-containing alloys are susceptible to attack by elemental sulfur and hydrogen sulfide as well as organically bound sulfur. Active or elemental sulfur and hydrogen sulfide gas can attack copper to form copper sulfide, a dark-brown to black compound. This can be seen through ASTM D-130 copper corrosion testing. 

Silver combines with sulfur to form a black compound, silver sulfide. That is why silver cutlery turns black when it comes into contact with egg, or certain green vegetables, that contain traces of sulfur. 

The rheological properties of gum and carbon black compounds of an ethylene-propylene terpolymer elastomer have been investigated at very low shear stresses and shear rates, using a sandwich rheometer [50]. Emphasis was given to measurements of creep and strain recovery at low stresses, at carbon black flller contents ranging between 20 and 50% by volume. The EPDM-carbon black compounds did not exhibit a zero shear rate viscosity, which tended towards in-Anity at zero shear stress or at a finite shear stress (Fig. 13). This was explained... 

Several mercurous salts absorb ammonia in the dry state or react with ammonia in aqueous solution. The products formed have been described from time to time as ammino-mercurous compounds. It appears, however, that these supposed mercuro-ammines are nonexistent, and that the substances produced by the action of ammonia are really mercuric derivatives mixed with mercury. For instance, mercurous fluoride in the dry state is blackened by ammonia gas, forming a compound HgF(NH3). This substance gives off ammonia at 100° C. and is black in colour the colour is now regarded as being due to finely divided mercury, and the compound as a derivative of mercuric fluoride and not of mercurous fluoride. Numerous instances of the same kind may be quoted. For example, mercurous chloride with aqueous ammonia yields a black compound this again has been proved to be a mixture of finely divided mercury and mercuric chloroamidc. The reaction may be represented thus ... 

Tetrahedral blue-black compounds [VL4](SCN)3 (L = en or Me4en) were prepared188 from K3[V(NCS)6] and their electronic spectra are comparable to other tetrahedral vanadium(III) complexes with substituted pyridines (see Section 33.4.3.2). 

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