Carbon disulfide-insoluble sulfur

When urea is coated with pressure-atomized sulfur at about 180 °F and quickly cooled, a mosaic texture is developed, as in the cross section of the sulfur coating in Figure 15. This mosaic texture is well developed and is characterized by high ratios of the areas of crystalline to carbon disulfide-insoluble sulfur. The mosaic texture in such samples is different... 

The gray metallic form of selenium is its most stable modification. It constitutes lustrous gray to black hexagonal crystals density 4.18 g/cm at 20° melts at 217°C soluble in sulfuric acid and chloroform very slightly soluble in carbon disulfide insoluble in alcohol. 

Tables Molecular composition of equilibrated liquid sulfur (mass %) after quenching the melt from temperatures of between 116 and 387 °C to -196 °C. is the fraction insoluble in carbon disulfide (polymeric sulfur)... 

Figure 4. Elastic deformation of Figure 5. Carbon disulfide-insoluble amorphous sulfur along a surface sulfur elastomer in the cross section...

Sulfur is pale yellow, odorless, brittle solid, which is insoluble in water but soluble in carbon disulfide. In every state, whether gas, liquid or solid, elemental sulfur occurs in more than one allotropic form or modification these present a confusing multitude of forms whose relations are not yet fully understood. 

Sulfur is insoluble in water but soluble to varying degrees in many organic solvents, such as carbon disulfide, ben2ene, warm aniline, warm carbon tetrachloride, andUquid ammonia (18). Carbon disulfide is the most commonly used solvent for sulfur. 

Quantitatively, sulfur in a free or combined state is generally determined by oxidizing it to a soluble sulfate, by fusion with an alkaH carbonate if necessary, and precipitating it as insoluble barium sulfate. Oxidation can be effected with such agents as concentrated or fuming nitric acid, bromine, sodium peroxide, potassium nitrate, or potassium chlorate. Free sulfur is normally determined by solution in carbon disulfide, the latter being distilled from the extract. This method is not useful if the sample contains polymeric sulfur. 

Acetaldehyde Cyanohydrin. This cyanohydrin, commonly known as lactonitnle, is soluble in water and alcohol, but insoluble in diethyl ether and carbon disulfide. Lactonitnle is used chiefly to manufacture lactic acid and its derivatives, primarily ethyl lactate. Lactonitnle [78-97-7] is manufactured from equimolar amounts of acetaldehyde and hydrogen cyanide containing 1.5% of 20% NaOH at —10 20 ° C. The product is stabili2ed with sulfuric acid (28). Sulfuric acid hydroly2es the nitrile to give a mixture of lactic acid [598-82-3] and ammonium bisulfate. 

Amorphous forms exhibit two colors, occurring as a red powder of density 4.26g/cm3 that has a hexagonal crystal structure and a black vitreous solid of density 4.28g/cm3. The red amorphous selenium converts to the black form on standing. Amorphous selenium melts at 60 to 80°C insoluble in water reacts with water at 50°C when freshly precipitated soluble in sulfuric acid, benzene and carbon disulfide. 

Crystalline selenium exhibits two monochnic forms an alpha form constituting dark red transparent crystals, density 4.50 g/cm. The alpha form converts to a metastable beta form of hexagonal crystal structure when heated to about 170°C. Both the crystalline forms are insoluble in water soluble in sulfuric and nitric acids very slightly soluble in carbon disulfide. Also, both the crystalline forms convert into gray metallic modification on heating. 

Sulfur vaporizes at 444.6°C. The element, particularly in its orthorhombic Ss form, is insoluble in water but dissolves in carbon disulfide, anhydrous liquid ammonia, and methylene iodide. It is moderately soluble in benzene, toluene, chloroform, and acetone, solubility increasing with temperature. Solid polymeric sulfur is practically insoluble in all solvents. 

Silvery-white lustrous metal when pure or dark gray amorphous powder orthorhombic crystals hardness 2.3 Mohs density 6.25 g/cm melts at 452°C vaporizes at 990°C modulus of elasticity 6.0x10 psi thermal neutron absorption cross section 4.7 0.1 barns insoluble in water, carbon disulfide, and benzene also insoluble in HCl soluble in sulfuric acid, nitric acid, and aqua regia also soluble in caustic potash and in solutions of alkali metal cyanides. 

Still another type of bewildering complexity (not shown in Fig. 7.5) is found in the liquid region, where two distinct liquid allotropic forms are known, called A-sulfur and ijl-sulfur. The former is the molten form commonly encountered in the laboratory pale yellow, diamagnetic, easily soluble in nonpolar solvents such as carbon disulfide, and of rather ordinary viscosity. The /x-sulfur variant, by contrast, is extremely viscous, deep orange-red, paramagnetic (indicative of radical unpaired-electron character), and essentially insoluble in any common solvent. These surprising differences point to essentially different coordination and bonding patterns at the microscopic level, as will be discussed in Chapter 13. 

Excellent solvent for many organic compounds dissolves phosphorus, sulfur, and halogen acids miscible with water, alcohol, glycerol, ether, and carbon tetrachloride practically insoluble in carbon disulfide.1... 

The free dimeric 9-molybdophosphoric(V) and 9-tungstophosphoric(V) acids are exceptionally soluble in water (up to 85% by weight of solution), ether, absolute alcohol, and cold nitric acid. However, they are insoluble in nonpolar solvents such as chloroform, carbon disulfide, or hydrocarbons. The 2 18 arsenic acid is decomposed by hydrochloric and sulfuric acids. 

O Carbon disulfide is used as a solvent for water-insoluble compounds, such as fats, oils, and waxes. Calculate the mass of carbon disulfide that is produced when 17.5 g of carbon reacts with 225 g of sulfur dioxide according to the following equation ... 

The reaction products were examined initially by extraction with carbon disulfide to give, in many cases, a fraction soluble in carbon disulfide. In every case all the unreacted free sulfur reported in Table II was soluble in carbon disulfide, indicating that it is non-polymeric and presumably ring material. The amount of insoluble material formed increases with reaction time. This insoluble fraction is a high-molecular-weight, cross-linked material, which swells in carbon disulfide and has an elemental analysis which corresponds to C10H12S11. Further examination has not been possible because of its intractable nature. 

Orthorhombic and Monoclinic Sulfur. Sulfur exists in several allotropic forms. Ordinary sulfur is a yellow solid substance which forms crystals with orthorhombic symmetry it is calleo orthorhombic sulfur or, usually, rhombic sulfur. It is insoluble in water, but soluble in carbon disulfide (CSg), carbon tetrachloride, and similar non-polar solvents, giving solutions from which well formed crystals of sulfur can be obtained (Fig. 17-1). Some of its physical properties are given in Table 17-1. 

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