Grey Powder

Technetium and rhenium differ markedly from manganese, but they are very similar to each other. They have little cationic chemistry, few compounds in the oxidation state II, more extensive chemistry in the IV and V states. The metals resemble Pt in their appearance (usually, however, they are in the form of a grey powder) they tarnish slowly in moist air, do not react with water. Metal dust is a fire and explosion hazard. 

The commercial product is usually dark grey powder, but the color may vary from ohve geeen to brown depending on particle size density 6.44 g/cm, which also may vary between 5.7 to 6.7 g/cm, depending on the method of preparation melts around 1,830°C insoluble in water soluble in acids and alkalis. 

Hexaethylenediamino-hexol-tetrachromic Sulphate, [Cr4(OH)6en6](SO4)3.10H2O, is prepared from partially dehydrated chromic alum. The bluish-grey powder obtained is heated with ethylene-diamine monohydrate on a water-bath till a red-coloured mass is produced, which consists of a mixture of potassium sulphate, luteo-chromic sulphate, and the sulphate of the hexol compound, and from the mixture the latter compound is obtained by dissolving out the more soluble salts with water. The crude, difficultly soluble sulphate is purified by dissolving in dilute sulphuric acid and reprecipitating with excess of ammonia. It crystallises in small needles which are almost insoluble in water and soluble in dilute acids. 

Trihydroxylamino-manganous Carbonate, [Mn(NH20H)3]C03. 2HaO, is produced as a white or grey powder when a solution of sodium carbonate and hydroxyl amine hydrochloride is added to an aqueous solution of manganous chloride.9... 

In dry air tellurium monoxide is a stable, amorphous, grey powder, or a porous solid, to which a graphitic lustre can be imparted by pressure. It is slowly oxidised in moist air and also when heated in dry air, being converted into the dioxide. 

Nickel Di-arsenide, NiAs2, occurs in Nature as chloanthite and ram-melsbergite (p. 12). It may be prepared by heating either of the two previously described arsenides with arsenic in an atmosphere of hydrogen at decreasing temperatures the arsenic is absorbed and the di-arsenide forms as a grey powder as the temperature falls below 100° C.2... 

Manganic Orthoarsenate, Mna(As04)2.2H20, may be prepared by treating a hot aqueous solution of arsenic acid with a concentrated solution of manganese nitrate.10 It forms a dark grey powder which dissolves slowly in hydrochloric acid but is insoluble in nitric acid. When heated to redness it forms manganous pyroarsenate. 

Iron Dark grey powder Attracted to it Very little action when cold. When warm, a gas is produced with a lot of bubbling (effervescence)... 

Grey powders, acquiring metallic lustre under the burnisher —thorium, niobium, tungsten. 

A more detailed study of the pyrolysis of H3SiMn(CO)5 in a sealed tube for various periods of time at 450°C showed that the volatile products were H2, CO, SiH. , and CH4 a metallic-looking brown film covered the walls of the tube, and an apparently amorphous grey powder was also present (33). Figure 5 shows that hydrogen and methane are produced in increasing amounts as the reaction proceeds, while CO reaches a steady concentration after about 10 min. Silane reaches a maximum concentration after about 5 min, then decreases to zero after 60 min. silane is known to decompose to silicon and hydrogen above about 425°C (368), and its presence is readily accounted for by the disproportionation reaction (109). 

Raw stock metallic tin (grey powder, 99.5% of the main substance) octylbromide (the boiling point is 201-204 °C) crystalline iodine (the melting point is 112.5-114 °C) triethylamine (the boiling point is 89-90 °C). 

Dihydrogen telluride is an acid in aqueous solution and is comparable in strength with phosphoric acid. Tellurols, especially arenetellurols, are expected to be at least as acidic as dihydrogen telluride. Therefore, tellurols should react easily with alkali metal hydroxides to form alkali metal tellurolates. Because tellurols are difficult to prepare, alkali metal tellurolates are best obtained by methods which avoid the tellurols. Sodium and lithium tellurolates are the most frequently used tellurolates. Although the tellurolates are not as sensitive to oxidation as the tellurols, tellurolates are almost always used in situ and are prepared and stored under nitrogen. Sodium benzenetellurolate was isolated as a moisture-and air-sensitive, grey powder. Its solutions in tetrahydrofuran or acetone were found to be stable for months when kept under nitrogen6. 

Potassium benzenetellurolate was obtained when diphenyl ditellurium suspended in liquid ammonia was treated with a solution of potassium in liquid ammonia. The reaction was carried out with a molar ratio of potassium diphenyl ditellurium of 2 1. Evaporation of the ammonia from the filtered reaction mixture left the potassium benzenetellurolate as a grey powder in 95% yield. The tellurolate was purified by washing with dry petroleum ether1. 

Grey powdered tellurium and lithium (2-lithiophenyl)acetylide reacted in tetrahydrofuran to produce benzotellurophene in 85% yield. The dilithium compound was prepared from phenylacetylene1. 

Cobalt nitride is a dull grey powder, readily soluble in hydrochloric and sulphuric aci.ds, yielding cobaltous salts, the nitrogen being liberated as ammonia. At 600° C. it evolves nitrogen, so that the formation of cobalt nitride can only proceed within very narrow limits of temperature. It is completely decomposed when heated in hydrogen or steam in the latter case the reaction proceeds slowly. 

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