Abstract: A method of recovering metallic tellurium from a residue dust containing a major amount of lead oxide, a minor amount of tellurium oxide, and a minor amount of iron oxide which comprises the steps of introducing the residue into a leach tank containing water, sulphuric acid and ferric sulphate, the sulphuric acid being present in the leach tank in an amount equal to about 5% to 10% by weight in excess of that stoichiometrically required to react with the lead and tellurium, the ferric sulphate being added as an oxidizing agent, reacting the residue with the sulphuric acid and ferric sulphate to produce lead sulphate and a tellurium solution, removing the lead sulphate and tellurium solution from the leach tank and separating the lead sulphate from the tellurium solution, adding the separated tellurium solution to a tumbler containing particles of metallic iron, agitating the tumbler so that the tellurium solution reacts with the iron to produce ferrous sulphate and metallic tellurium, withdrawing the mixture

Abstract: In a method of making concrete of the Portland Cement type wherein a quantity of cementitious material, such as Portland Cement, is mixed with a quantity of aggregate, generally sand and rock in varying proportions and water; and, wherein, the resulting mixture is stirred or mixed for an appropriate length of time consistent with acceptable practices in the concrete industry after which the mix is poured and allowed to set, the improvement which is characterized by the employment of fly ash as the major ingredient in the cementitious material. The improvement also includes the adding of gypsum to the initial mix in an amount equal to about 2% by weight of the fly ash and, thereafter, adding in and mixing a quantity of calcium chloride equal to about 3% by weight of the fly ash.