Thiocarbonate precipitants

A number of substances, such as the most commonly used sulfur dioxide, can reduce selenous acid solution to an elemental selenium precipitate. This precipitation separates the selenium from most elements and serves as a basis for gravimetry. In a solution containing both selenous and teUurous acids, the selenium may be quantitatively separated from the latter by performing the reduction in a solution which is 8 to 9.5 W with respect to hydrochloric acid. When selenic acid may also be present, the addition of hydroxylamine hydrochloride is recommended along with the sulfur dioxide. A simple method for the separation and deterrnination of selenium(IV) and molybdenum(VI) in mixtures, based on selective precipitation with potassium thiocarbonate, has been developed (69). 

To a solution of diacetone-cx-D-glucofuranose [Eq. (8)128 (1 g, 3.84 mmol), At-hydroxysuc-cinimide (NHS, 0.044 g, 0.384 mmol), and dry pyridine (0.93 mL, 11.52 mmol) in C6H6 (20 mL) was added pentafluorophenyl chlorothionoformate (1.54 mL, 9.6 mmol) dropwise at room temperature under argon. The solution was stirred for an additional 2 h. The organic layer was washed with 1 M HC1, saturated NaHCOj, brine, and dried over anhydrous MgS04. After evaporation of the solvent under reduced pressure, the thiocarbonate byproduct was precipitated with hexanes. After filtration and evaporation, the crude product was purified by column chromatography over silica gel (eluting with n-hexane-EtOAc 8 2) to afford 1.45 g (77%) of the thionocarbonate 31 mp 65°-66°C. 

Chromium Thiocarbonate.—AVhen calcium thiocarbonate is added to a solution of a chromic salt, a grey-green precipitate resembling chromic hydroxide is produced, which on distillation yields carbon disulphide and a brown residue of chromium sesquisulphide, CrjSg, which burns vividly in air, forming chromium sesquioxide. 

Diaryl thiocarbonates 756,759 A monohydric phenol (2 moles) is dissolved in a small excess of 10% sodium hydroxide solution, diluted with the four- to five-fold amount of water, and treated gradually, with vigorous shaking, with thiophosgene (1 mole). If the mixture becomes too warm it must be cooled. The aryl ester produced separates as a white precipitate and is washed free from alkali by water and recrystallized, generally from ethanol. 

Ammonium pentasulfide (see p. 369) is digested with CSg in a wide-neck flask equipped with a reflux condenser and an immersed, water-cooled coil. Colorless (NH )2S precipitates on the cold surface of the cooling tube, but is later converted to the pale orange-yellow thiocarbonate. 

Carbonates, Thiocarbonates, and Related Anions, The syntheses of carbonates, hydroxide carbonates, and oxide carbonates have been reported. Those factors which influence the crystallization of rare-earth carbonates have been investigated the carbonates were precipitated at various temperatures from aqueous solutions by using sodium carbonate (20—80 C), sodium bicarbonate (20—80 °C), trichloroacetic acid (40—120 °C), and urea (50—150 °C) as precipitants. The carbonates so formed were characterized by chemical analysis and A"-ray powder diffraction techniques. It was found that they could be classified into several phases (Table 19) according to the ionic radii... 

Synonyms Sodium thiocarbonate Empiricai CNa2Ss Formula S=C(SNa)2 Properties M.w. 154.19 Uses Metal precipitant for treatment of wastewater and other heavy metal-contg. liqs. insecticide... 

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