Particles lead selenide

Fig. Vni-3. (a) Atomic force microscope (AFM) and (b) transmission electron microscope (TEM) images of lead selenide particles grown under arachidic acid monolayers. (Pi Ref. 57.)...

Gobet and Matijevic (17) produced monodisperse submicrometer-size particles of cadmium selenide (CdSe) and lead selenide (PbSe) by reversible release of selenide ions from selenourea in solutions of the corresponding metal salts. The equilibrium between selenourea and selenide ions is written as follows ... 

Metals less noble than copper, such as iron, nickel, and lead, dissolve from the anode. The lead precipitates as lead sulfate in the slimes. Other impurities such as arsenic, antimony, and bismuth remain partiy as insoluble compounds in the slimes and partiy as soluble complexes in the electrolyte. Precious metals, such as gold and silver, remain as metals in the anode slimes. The bulk of the slimes consist of particles of copper falling from the anode, and insoluble sulfides, selenides, or teUurides. These slimes are processed further for the recovery of the various constituents. Metals less noble than copper do not deposit but accumulate in solution. This requires periodic purification of the electrolyte to remove nickel sulfate, arsenic, and other impurities. 

More commonly, selenium enters the air from burning coal or oil. Much of the selenium in air is attached to fly ash and to suspended particles. The elemental selenium that may be present in fossil fuels forms selenium dioxide when burned. Selenium dioxide can then form selenious acid with water or sweat. Selenium anhydride is released during the heating of copper, lead, and zinc ores when there is selenium in them. Hydrogen selenide breaks up rapidly in air to form elemental selenium and water, thus eliminating the danger from this compound for most people, except those who are exposed to it in their workplace. 

Figure 8. Schematics of the pyrolysis process leading to the formation of the ruthe-nium-selenide cluster-like compound. The hep-symmetry of the 153 atoms clusterlike particle (see right) fits the experimental points in Figure 7 (continuous line).

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