Lead sulphide, oxidation

If the normal carbonate is used, the basic carbonate or white lead, Pb(OH),. 2PbCO,. is precipitated. The basic carbonate was used extensively as a base in paints but is now less common, having been largely replaced by either titanium dioxide or zinc oxide. Paints made with white lead are not only poisonous but blacken in urban atmospheres due to the formation of lead sulphide and it is hardly surprising that their use is declining. 

Lead The production of lead from lead sulphide minerals, principally galena, PbS, is considerably more complicated than the production of zinc because tire roasting of the sulphide to prepare the oxide for reduction produces PbO which is a relatively volatile oxide, and therefore the temperature of roasting is limited. The products of roasting also contain unoxidized galena as well as die oxide, some lead basic sulphate, and impurities such as zinc, iron, arsenic and antimony. 

By oxidative addition of aryl sulphides to low-valent nickel complexes, a C—S bond cleavage occurs to form Ni11 thiolate complexes. For example, exposure of diaryl sulphides to [(But3P)3Ni0] leads to oxidative addition, with nickel inserting into the C—S bond (280).814... 

Flotation of Mixed Lead Zinc Sulphide Oxide and Oxide Lead and Zinc Ores... 

SULPHIDE OXIDE AND OXIDE LEAD ZINC ORES... 

There are a variety of mixed sulphide oxide ores and oxide lead zinc ores, and these ores cannot be classified into any specific group due to the vast differences in geology and mineral compositions. Only limited literature is available on the geological and miner-alogical characteristics of these ores. From a processing point of view, these ores can be classified into the following groups ... 

Mixed sulphide oxide lead zinc ores... 

The beneficiation of mixed lead zinc sulphide oxide ores is a complex process and is dependent on gangue composition of the ore. There are two basic types of mixed sulphide oxide ores that have been extensively studied. These include (a) ores with dolomitic and... 

Treatment of mixed lead zinc sulphide oxide ores with dolomitic and calcite gangue... 

These ore types are abundant in Northern Canada and Mexico. Extensive research work was carried out on these ores with the objective of developing a treatment process for commercial application. One of the major tasks in the development testwork was to use a non-cyanide flotation method in the sulphide flotation. Typical reagent schemes used in beneficiation of the mixed lead zinc oxide sulphide ores are shown in Table 20.5. 

Reagent schemes used for mixed lead zinc oxide sulphide ores [10]... 

Continuous locked cycle test results from mixed lead zinc sulphide oxide ore... 

There are only few operations treating mixed lead zinc sulphide oxide ores that contain barite-calcite gangue minerals. A typical example of such an operation is the Tynagh oxide complex in Ireland [11]. In this deposit, the oxide ores are generally located at the bottom and at the ends of the sulphide mud ores. The major gangue mineral is barite (large quantities) and minor amounts of clay. This ore assays 8.5% Pb(total), 6% Pb(oxide), 6.8% Zn(total) and 5% ZnO. 

Reagent scheme used for treatment of the Tynagh mixed sulphide oxide lead zinc ore... 

J. J. Berzelius prepared lead phosphate by adding a soln. of lead acetate to a nitric acid soln. of bone-ash, and decomposed the lead phosphate by treatment with dil. sulphuric acid, and removed the last traces of lead by hydrogen sulphide and W. Odling treated a soln. of sodium phosphate in ice-cold water with lead acetate, and decomposed the washed precipitate suspended in water with hydrogen sulphide. The soln., freed from the precipitated lead sulphide, was evaporated to remove the hydrogen sulphide. J. Persoz digested the soln. of bone-ash with ferric or aluminium oxide, decomposed the precipitated phosphate with sulphuric acid, and afterwards extracted with phosphoric acid with alcohol. L. Thompson precipitated the lime by treating the calcium phosphate with oxalic acid. W. H. Ross and co-workers purified phosphoric acid by a process of fractional crystallization. 

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