Bismuth, electrolytic production

Crude lead contains traces of a number of metals. The desilvering of lead is considered later under silver (Chapter 14). Other metallic impurities are removed by remelting under controlled conditions when arsenic and antimony form a scum of lead(II) arsenate and antimonate on the surface while copper forms an infusible alloy which also takes up any sulphur, and also appears on the surface. The removal of bismuth, a valuable by-product, from lead is accomplished by making the crude lead the anode in an electrolytic bath consisting of a solution of lead in fluorosilicic acid. Gelatin is added so that a smooth coherent deposit of lead is obtained on the pure lead cathode when the current is passed. The impurities here (i.e. all other metals) form a sludge in the electrolytic bath and are not deposited on the cathode. 

The Sperry process for making white lead ia an electrolytic cell recovers bismuth as a by-product ia the anode slimes. 

The final ceU product contains 250—300 g/L H2SO in the last stages of electrolyte purification, and antimony and bismuth precipitate, resulting in heavily contaminated cathodes that are recycled through the smelter. Arsenic and hydrogen evolved at the cathodes at these later stages react to form arsine, and hoods must be provided to collect the toxic gas. 

By-Product Recovery. The anode slime contains gold, silver, platinum, palladium, selenium, and teUurium. The sulfur, selenium, and teUurium in the slimes combine with copper and sUver to give precipitates (30). Some arsenic, antimony, and bismuth can also enter the slime, depending on the concentrations in the electrolyte. Other elements that may precipitate in the electrolytic ceUs are lead and tin, which form lead sulfate and Sn(0H)2S04. 

Bismuth salicylate has a number of properties contributing to its antidiarrheal effects. This drug may stimulate water and electrolyte absorption from the lower GI tract, thus decreasing fecal fluid loss. In addition, the bismuth component of this compound may have antibacterial effects, and the salicylate component may inhibit the production of prostaglandins that irritate the intestinal lining. The combination of these properties makes this drug fairly effective in... 

Most metals entering the cuprate HTSC (with the exception of copper) during anodic polarization in aqueous solutions over a wide pH interval form either soluble products or loose oxide-hydroxide films with a poor adhesion. The passivation of such chemically active metals in electrolyte solutions has been incompletely studied. However, for bismuth, cadmium, antimony, and also for the corresponding chalco-... 

At primary refineries (whether thermal or electrolytic), silver and gold are valuable by-products. Copper is easUy removed from bullion and will normally be sold in matte or speisse form. Arsenic, antimony, tin, bismuth and some other minor metals may also arise as by-products at electrolytic refineries, but this is not widespread. Their removal is costly, and where a saleable by-product is not produced, they are considered penalty elements (see Appendix B for details of recent price trends in minor metal by-products). At secondary smelter/refineries the trend is similarly towards increased by-product recovery. As weU as antimony, the key materials here are plastic (or polypropylene), and less commonly sodium sulphate (for detergent manufacture). 

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