| 摘要 |
<p>Precious metals or their minerals such as tellurides, selenides &c. are concentrated by flotation in a pulp containing a small amount of one or more of the sulphides or sulpho-salts or mixtures of sulphides and sulpho-salts of lead, mercury, silver, and p copper, a portion of each sulphide or sulpho-salt being initially present in or added to the pulp in granular or crystalline condition and another portion being added to or generated in the pulp in highly divided or colloidal condition. The term "sulpho-salt" is used to define a compound of the metal with sulphur and arsenic or antimony. Naturally occurring sulphides may be used, reduced by disintegration to a mixture of crystalline and colloidal particles, or the mixture may be produced artificially by slow precipitation of the sulphide from a soluble salt such as the acetate with sulphuretted hydrogen or an alkali sulphide. The mixture may be produced in the pulp by adding a soluble salt of the metal and precipitating with sulphuretted hydrogen, artificially prepared or natural sulphide in a crystalline condition being added separately if necessary, if not initially present in the pulp. If pyrites is present in the ore, this may either be floated with the precious metal or may be depressed, e.g. with potassium cyanide. In the flotation process the pulp may be slightly alkaline, xanthate may be used as a collecting agent and aerofloat or cresol as frothing agent. It is stated that the sulphides, when present as a mixture of crystalline and colloidal particles, form linked compounds by adsorption with the precious metals or their minerals.</p> |
