Polysulfides sulfur pressure

The sulfur pressure over liquid sodium polysulfides has been measured in the temperature range 400-1000 °C [26]. 

The process of sulfurization is usually carried out by a sulfur bake, in which the dry organic starting material is heated with sulfur between 160 and 320°C a polysulfide bake, which includes sodium sulfide a polysulfide melt, in which aqueous sodium polysulfide and the organic starting material are heated under reflux or under pressure in a closed vessel or a solvent melt, in which butanol, CeUosolve, or dioxitol are used alone or together with water. 

The manufacture of sulfur dyes involves sulfurisation processes, the chemistry of which remains rather mysterious and may arguably be considered still to be in the realms of alchemy The processes involve heating elemental sulfur or sodium polysulfide, or both, with aromatic amines, phenols or aminophenols. These reactions may be carried out either as a dry bake process at temperatures between 180 and 350 °C or in solvents such as water or aliphatic alcohols at reflux or at even higher temperatures under pressure. C. I. Sulphur Black 1, for example, is prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

Initially, sulfur dyes were water-insoluble, macromolecular, colored compounds formed by treating aromatic amines and aminophenols with sulfur and/or sodium polysulfide. R. Vidal developed these dyes in 1893 but they only became attractive for leather with the introduction of water-solubilizing groups. Today, the sulfur dyes can be divided into three classes conventional water-insoluble, leuco, and solubilized sulfur dyes. Most sulfur dyes are synthesized by condensation of aromatic amines with sulfur or sodium polysulfide in the so-called bake process, or else in water or under pressure as a solvent-reflux reaction. 

The Kindler modification dodges heating in closed vessels under pressure by using, instead of aqueous ammonium polysulfide, a mixture of sulfur and morpholine. After being refluxed for 6-12 h, the ketone is converted into the thiomorpholide of the carboxylic acid. Subsequent alkaline hydrolysis yields the carboxylic acid as the final product [501, 503, 504, 1170]. 

Most polysulfides with a sulfur rank higher than three, are mixtures where the different sulfur ranks coexist in equilibrium (Table 4). In many cases elemental sulfur is also involved in the above equilibrium. Changes in temperature and pressure sometimes alter this equilibrium and precipitate sulfur. Viscosity of the polysulfides also is a function of temperature, increasing dramatically with decreasing temperature. In most cases heating polysulfides results in their decomposition to the alkyl mercaptans. Some of the aromatic polysulfides are tacky solids. Many trisulfides can be isolated as pure compounds, and exhibit unique chemical properties. They are the only polysulfides that are not corrosive to copper. 

The higher dialkyl polysulfides, such TNPS, find use as extreme-pressure lube additives, especially for cutting oils the lower dialkyl polysulfides, such as (CH3)2S as sulfur-donor agents, for example, to convert phosphites to thiophosphates ... 

A suspension of 20.1 g 1,5-dimethoxy-2,4-dinitrobenzene (90.0 mmol) in 117 mL water was stirred under reflux and treated dropwise over 30 min with a solution of sodium polysulfide, prepared by heating 28.6 g Na2S-9H20 (119 mmol) and 6.8 g sulfur (213 mmol) in 120 mL water. The reaction mixture was stirred under reflux for a further 3 h and then cooled and evaporated under reduced pressure at 45°C to give a dark residue. This was extracted several times with warm EtOAc, and the combined extracts were filtered through a short column of silica gel. The eluates were washed with water and evaporated to dryness. The residue was dissolved in 1 N HCl, filtered, and basified with aqueous NaOH to give 11.0 g l-amino-2,4-dimethoxy-5-nitrobenzene, in a yield of 63%, m.p. 126-128°C. 

Second, there is no reproducibility of the resulting compositions in duplicate experiments. Third, die final products of the same gross composition reactions, for instance, R+2S or RS. 50+0-5S, are not always identical, and depend on the origin of the starting products and the sequence of temperature and pressure variation. With these principles, one can suggest that the powdered polysulfides prepared by different authors (see sect. 3.3) can hardly be related to equilibrium materials. A multiphase surface state of powders has a serious effect on many properties and, thus, merits detailed consideration here. It is apparent that special means must be used to provide data on the gross composition and the spatial variation of the sulfur content over the grain. 

The solidus portion of the pressure-dependent equilibrium phase diagram of the PrS2,o-PrSi,5 system constructed by methods (a) and (b) is shown in fig. 4. A series of new sulfur-deficient polysulfides, PrSi.9oo(2), PrSi.846(6)i PrSi 756(8), and PrSi.702(7), in addition to tlie strict stoichiometric PrS2 has been found, separated by miscibility gaps. The intermediate polysulfides are seen to have narrow fields of stability. Therefore, it is difficult to prepare a single-phase intermediate polysulfide, especially when the desired thermodynamic parameters are unknown. On the other hand, the information resulting from these diagrams on the nonstoichiometric polysulfide compositions opens... 

To produce viscose silk (rayon), the next stage is spinning under 3-5 bar pressure into what is known as a Muller bath, which consists of 7-12% H2SO4, 16-23% Na2S04, and 1-6% Zn-Mg-NH4-sulfate. Here, two events occur simultaneously coagulation of the cellulose xanthate and hydrolytic decomposition to cellulose with the reformation of CS2. As by-products, H2S and COS are found in the exhaust air and elementary sulfur (as sodium polysulfides) in the bath and on the fibers. Sodium sulfate should decrease dissociation and thus lessen the osmotic pressure drop of the bath with its high electrolyte content relative to the fiber gel, which is low in electrolytes. 

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