Thallous sulfide

The relative toxicities of thallium compounds depend on their solubilities and valence states. Soluble univalent thallium compounds, eg, thallous sulfate, acetate, and carbonate, are especially toxic. They are rapidly and completely absorbed from the gastrointestinal tract, skin peritoneal cavity, and sites of subcutaneous and intramuscular injection. Thallium is also rapidly absorbed from the mucous membranes of the respiratory tract, mouth, and lungs following inhalation of soluble thallium salts. Insoluble compounds, eg, thallous sulfide and iodide, are poorly absorbed by any route and are less toxic. 

Impurities sensitize some azides. For example, Gray and Waddington [18] introduced thallous sulfide into thallous azide and found that the initiation temperature was lowered. For pure lead azide the initiation temperature was 763°K whereas for the impure lead azide it was 693°K. Similarly, lead azide crystals containing 1% of carbon particles of size less than 1 /im initiate at temperatures below that of the pure lead azide [19]. An interesting method for introducing small quantities of impurities into silver azide was used by Deb et al. [20]. They prepared silver azide by using radioactive Ag, which decays by j3-emission into Cd. This method allowed 10" % of impurity to be introduced. It is important that even such small quantities affected not only the sensitivity but also the... 

A. Elemental Selenium (1) Test through addition to thallous sulfide ... 

Elemental red selenium, like sulfur, when dissolved in organic liquids, reacts with thallous sulfide paper (see page 433). An addition compound is formed which is resistant to dilute acids and hydrogen peroxide. Since it is black, it cannot be seen on the black thallous sulfide paper, in contrast to the analogous red-brown compound formed by considerable quantities of sulfur. However, the unaltered thallous sulfide can be dissolved away by bathing the paper in dilute acid or hydrogen peroxide solution, and the spot at which the drop of selenium solution was applied then shows up as a dark brown to black fleck. The latter consists of the selenide-sulfur complex, or of thallous sulfide, protected from the action of the solvents by a coating of the complex. 

Procedure. Freshly prepared thallous sulfide paper is spotted with a drop of the solution to be tested for sulfur. The solvent (carbon disulfide, pyridine, etc.) is allowed to evaporate at room temperature or is removed by a blast of heated air. The spotted paper is then placed in 0.5 iV nitric acid and swirled. If no sulfur (or selenium) is present, the whole paper turns white in about 30 seconds a brown fleck is left if these elements are present. The intensity of the color depends on the quantity of sulfur. It is well to place the paper in water after the fleck has developed this prevents any further action of the acid and a gradual fading of the spot. 

Thallous sulfide paper is prepared by bathing filter paper (S S 589 or Whatman 42) in 0.5 % solution of thallous carbonate or acetate for several minutes. The liquid is allowed to drain off and the paper is dried in a blast of heated air. Thallous sulfide is deposited by placing the paper across a beaker containing ammonium sulfide solution warmed to 80° C. The conversion to thallous sulfide is rapid the paper turns perfectly black on the side exposed to the fumes. Cut into strips, it is ready for immediate use. It is best always to use freshly prepared reagent paper when testing for sulfur. The paper deteriorates on standing because the sulfide is partially oxidized. 

To detect free alkali in the presence of alkali sulfides, which also give an alkaline reaction owing to hydrolysis, use is made of the fact that thallous sulfide is insoluble whereas thallous hydroxide is soluble in water and is almost as strong a base as potassium hydroxide. Free alkali may be detected by adding neutral thallous nitrate and then testing the solution for an alkaline reaction. 

Procedure. A drop of the test solution is mixed on a spot plate with 1 or 2 drops of a saturated solution of thallium nitrate, and stirred. A strip of litmus paper immersed in the resulting suspension of thallous sulfide turns blue if free alkali is present. 

Uses. Thallium compounds have limited use in industrial applications. The use of thallous sulfate in rodenticides and insecticides has been replaced by other compounds less harm fill to animals (see Insect control technology Pesticides). Thallium sulfide has been used in photoelectric cells (see Photovoltaic cells). A thallium bromide—thallium iodide mixture is used to transmit infrared radiation for signal systems. Thallous oxide is used in the manufacture of glass (qv) that has a high coefficient of refraction. Thallium formate—malonate aqueous solutions (Cletici s solution) have been used in mineral separations. Many thallium compounds have been used as reagents in oiganic synthesis in research laboratories. 

The dominant oxidation states for thallium are the mono and trivalent states. The thallous ion (TU) is colorless has a radius of 1.4 A, and usually exists as a six- or eight-coordinate structure in crystalline salts [1,2]. The thallous ion can produce a base that is weaker than KOH (i.e., TlOH). Thallium can also be considered a soft Lewis acid its softness is attributed to its d ° electron configuration. A variety of water-soluble thallous salts exist including the cyanide, nitrate, carbonate, sulfate, and phosphate. Insoluble salts such as the chloride (TlCl) or the sulfide (TljS) also exist. 

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