Sulphur black compounds

The most important class of stabilisers are the lead compounds which form lead chloride on reaction with hydrogen chloride evolved during decomposition. As a class the lead compounds give rise to products of varying opacity, are toxic and turn black in the presence of certain sulphur-containing compounds but are good heat stabilisers. 

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). 

The first commercial sulphur dye was discovered accidentally in 1873 by Croissant and BretonniSre who heated lignin-containing organic waste, such as sawdust, with sodium polysulphide at about 300 °C the product was sold under the name Cachou de Laval [52]. Even today an equivalent dye (Cl Sulphur Brown 1) is derived from lignin sulphonate, which is readily available from waste liquors from wood pulp manufacture. The real pioneer of sulphur dyes was Vidal, the first chemist to obtain dyes of this type from specific organic compounds. In particular, Sulphur Black T (Cl Sulphur Black 1) was made from 2,4-dinitrophenol in 1899. At the turn of the century many of the intermediates available were subjected to sulphurisation (thionation), that is, treatment with sulphur, sodium sulphide or sodium polysulphide to introduce sulphur linkages. 

Cl Sulphur Black 1, which is produced from the relatively simple intermediate 2,4-dinitrophenol and aqueous sodium polysulphide. A similar product (Cl Sulphur Black 2) is obtained from a mixture of 2,4-dinitrophenol and either picric acid (6.148 X = N02) or picramic acid (6.148 X = NH2). A black dye possessing superior fastness to chlorine when on the fibre (Cl Sulphur Black 11) can be made from the naphthalene intermediate 6.149 by heating it in a solution of sodium polysulphide in butanol. An equivalent reaction using the carbazole intermediate 6.150 gives rise to the reddish blue Cl Vat Blue 43 (Hydron blue). This important compound, which also possesses superior fastness properties, is classified as a sulphurised vat dye because it is normally applied from an alkaline sodium dithionite bath. Interestingly, inclusion of copper(II) sulphate in the sulphurisation of intermediate 6.150 leads to the formation of the bluish black Cl Sulphur Black 4. 

Sulfur dyes are water-insoluble, macromolecular, colored compounds which are produced by bridging aromatic amines, phenols, and amino phenols with sulfur and/or sodium polysulfide [16], These dyes are of little interest for dyeing paper. Only C.I. Sulphur Black 1 (36), the most important dye of all in terms of volume, is used for special paper dyeings. 

Vidal and other sulphur blacks have been used for dyeing fast shades on pure silk by the method patented by Lodge and Evans. The process is based on the fact that Vidal Black can be converted into its leuco compound, which is soluble in ammonium sulphide, by the action of sulphites or bisulphites. In practice the leuco compound is prepared and dissolved in sodium sulphide, which is then converted into ammonium sulphide by the addition of ammonium sulphate. 

Another fairly toxic group of phenolic compounds present in wastewaters is that of the nitrophenols. They are toxic when applied perorally, as well as when inhaled or absorbed through the skin. The most toxic is 2,4-dinitrophenol employed in the dyestuff industry (sulphur black). In biochemical reactions, its inhibiting effect on the vital functions of the cell is known. The solubility of some nitrophenols is presented in Table 3.17. 

The tannin from gall-nuts is used in making writing inks. Ordinary inks were formerly made from an extract of galls to which a gum, ferrous sulphate, a trace of sulphuric acid, and a blue dye were added. The acid prevents the oxidation of the ferrous sulphate and thus renders the ink stable the dye gives a color to the solution so that the writing made with it can be seen. When the ink is placed on paper the alumina in the latter neutralizes the acid, and the ferric salt formed as the result of action of the air, reacts with the tannin and a black compound is produced. 

Sulphur Black is prepared by fusing dinitrophenol, C6H30H(1),(N02)2(2,4), with sulphur or by heating it with a strong solution of sodium polysulphide. The intermediate necessary is prepared from chlorodinitrobenzene which is formed by nitrating chlorobenzene. The chlorine atom is readily replaced by the hydroxyl group when the compound is warmed with a solution of caustic soda. 

Initially, silanes were used in compounds based on EPM containing calcined clay and which were intended for electrically insulating applications. It was noticed that the insulating properties were improved and stabilised, especially in a moist environment mechanical properties were also improved. The same type of improvement was noted with hydrated alumina. The most suitable coupling agent, with peroxide crosslinking, is vinyl tri( 1-methoxy-ethoxy) silane with sulphur and accelerator crosslinking systems mercaptopropyl trimethoxy silane is recommended. Silanes have recently been made available as masterbatches and can be added directly to mineral fillers.The use of silanes has now extended to non-black compounds for applications other than cables when silicas and other types of filler (aluminium and calcium silicates) are used. 

Sulphur and tellurium form a chloride of formula XClj. Sulphur dichloride SClj is a red liquid at room temperature whilst the corresponding tellurium compound is a black solid. 

If the original compound contains sulphur, a black precipitate may be produced at this stage. 

The UK Environment Agency deals with over 6000 oil pollution incidents each year. One estimate suggests tliat tlie cheiTtical industry contributes to 50% of all ah pollution witli proportions approximating to sulphur dioxide (36%), carbon dioxide (28%), nitrogen oxides (18%), carbon monoxide (14%) and black smoke (10%). Motor spirit refining is responsible for ca 26% of emissions of volatile organic compounds to the atmosphere. In 1996 there were over 20 000 reports of water pollution incidents with 155 successful prosecutions. 

Silver is attacked by most compounds of sulphur, becoming covered with a yellow, brown or black sulphide film. 

Metals tarnish when their surface atoms react with gaseous substances in the air. Oxygen is a highly reactive element, as we saw in the previous chapter, and it combines with iron to form the ruddy oxide compound we recognize as rust. Copper reacts with oxygen and carbon dioxide to form a greenish patina of copper carbonate. Silver resists the advances of oxygen but will slowly combine with sulphur compounds in the air to form black silver sulphide. 

Hydrochloric, nitric, and sulphuric acids transform the powder into black amorphous compounds containing acidic residues in place of tire hydroxo-groups.3... 

---