Monosulphides

Figure 11.15. Typical chemical groupings in a sulphur-vulcanised natural rubber network, (a) Monosulphide cross-link (b) disulphide cross-link (c) polysulphide cross-link (j = 3-6) (d) parallel vicinal cross-link (n = 1-6) attached to adjacent main-chain atoms and which have the same influence as a single cross-link (e) cross-links attached to common or adjacent carbon atom (f) intra-chain cyclic monosulphide (g) intra-chain cyclic disulphide (h) pendent sulphide group terminated by moiety X derived from accelerator (i) conjugated diene (j) conjugated triene (k) extra-network material (1) carbon-carbon cross-links (probably absent)...

Organic phosphates Tetramethyl thiuram monosulphide and disulphide... 

A term apphed to vulcanisation systems in which sulphur or a sulphur donor is used very efficiently for crosslinking the rubber. EV systems produce vulcanisates with crosslinks that are mainly monosulphidic, which are thermally and mechanically stable. 

The presence of sodium hexamethylene bis-thiosulphate results in the formation of hybrid polysulphidic/hexamethylene bonds. The polysulphidic portion of these hybrid bonds reverts to monosulphidic during reversion but stability is achieved by the presence of the hexamethylene. 

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... 

The diphosphine monosulphides (95) rearrange on heating, the sulphur migrating to the more basic phosphorus centre.92 Benzyl methanesulphenate (96) reacts with... 

Fig. 12.14 Redoxpotential, pH and dissolved exchangeable Mn and monosulphide of a soil as a funtion of time after inundation (Brummer, 1974, with permission).

Ni-S behaves rather similarly to Co-S (see Sec. 6.5, Cobalt). Note that the freshly precipitated monosulphides of both metals transform in solution to a more insoluble form-possibly M(OH)S. 

The few cases reported for CD sulphides and selenides of T1 all reported the monosulphide (selenide)—TIS or TlSe. T1 can be monovalent or trivalent, and these apparently divalent compounds are believed to be mixed-valence compounds, with both T1(I) and Tl(III) present. 

G. Taddei7 prepared potassium iodide by adding a dil. soln. of potassium monosulphide to an alcoholic soln. of iodine. In place pf potassium sulphide, J. von Liebig and C. Wittstock used barium sulphide, prepared by calcining sulphate with coke. According to R. Schindler, the products obtained by the sulphide process are contaminated with sulphur compounds. G. S. Serullas treated potassium antimoniate (prepared by calcining tartar emetic) with an alcoholic soln. of iodine as long as the soln. was decolorized. The filtered soln. was evaporated to the point of crystallization. 

The preparation of the alkali monosulphides.—Products usually called sulphides have been obtained by the direct union of the elements. Thus, L. Troost 2 prepared what he regarded as amorphous lithium sulphide, Li2S, by the action of sulphur vapour on heated lithium. H. Davy, and J. L. Gay Lussac and L. J. Thenard, prepared sodium sulphide, Na2S, by warming sulphur with sodium ... 

J. J. Berzelius melted sulphur with an excess of potassium hydroxide and found the product to be a mixture of the monosulphide and thiosulphate. J. Kircher passed hydrogen sulphide over coarsely powdered sodium hydroxide at 100°. M. J. Fordos and A. Gelis made sodium sulphide by heating sodium carbonate with sulphur to 275° the product is obviously a kind of soda-liver of sulphur. J. W. Kynaston melted sodium hydroxide With calcium sulphide and J. V. Esop, and C. Vincent treated a soln. of barium or other sulphide with sodium or potassium... 

H. Riesenfeld found the solubility of ammonia in soln. of sodium sulphide to be a linear function of the Na2S-conc. and they measured the ammonia press, of A-soln. of ammonia in sodium sulphide. With soln. containing 0 5, 1, and 1 5 mol. of sodium monosulphide, the respective press, of the ammonia were 15 18, 16 94, and 18 55 mm., when the press, of the ammonia in 2V-aq. soln. was 13 45 mm. According to W. P. Bloxam, potassium sulphide is stable at a low red heat and does not decompose when it is melted. P. Berthier stated that it is volatilized at high temp. When it is roasted in the air, potassium sulphide... 

Similar remarks apply to the f.p. curve of mixtures of potassium monosulphide and sulphur. 

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