Lead sulphate residue

It is rarely necessary to determine quantitatively the separate components of the residue. When the lead sulphate is to be determined, the residue is extracted with ammonium acetate solution in the hot, the liquid filtered and the filtrate precipitated with hydrogen sulphide the lead sulphide is dissolved in nitric acid, and the procedure indicated in the next section (6) followed. 

If necessary, lead sulphate may be determined in the residue in the way described for white lead (q.v., paragraph 5). 

Soluble Lead.—The nitric add solution from the preceding determination is evaporated with a little sulphuric acid first on a water-bath and then on a sand-bath until fumes of sulphuric acid appear. The cdd residue is taken up in water and the lead sulphate estimated as with white lead (q.v., paragraph 6). The lead thus found is that corresponding with the white lead contained in the product under examination. 

The part insoluble in dilute acid is digested in the cold with 50 c.c. of ammonium acetate solution (D 1-04), this dissolving the lead sulphate, which may be estimated by evaporating to dryness the filtrate and calcining the residue with a little sulphuric acid. 

Qualitative Analysis.—The minium is treated with dilute nitric acid effervescence indicates carbonates in the solution the lead is precipitated by means of hydrogen sulphide, the filtrate being tested for zinc, iron, aluminium, calcium and magnesium by the ordinary methods. The brown residue insoluble in nitric acid is heated further with nitric add in presence of either sugar solution or hydrogen peroxide until the lead dioxide is completely dissolved any insoluble residue then remaining may contain lead sulphate, barium sulphate or clay, which may be identified in the usual way. 

The pigment is treated with hydrochloric acid effervescence indicates copper or calcium carbonate any insoluble residue may contain barium sulphate, gypsum (in large quantity), lead sulphate or clay, which may be identified by the usual methods. The solution is treated with excess of ammonium carbonate if a precipitate forms, it is tested especially for alumina, lime and magnesia. 

The mechanically dressed ore is first roasted in order to remove sulphur, arsenic, and other volatile ingredients, and then heated in a reverberatory furnace with sodium carbonate or sodium sulphate. The product is extracted with %varm dilute sulphuric acid, whereupon the uranium passes into solution, whilst the radium remains in the residue witlr calcium, barium, and lead. Tliis residue, which is the starting material for tlie extraction of radium, also contains silica and small quantities of copper, bismutli, arsenic, antimony, iron, aluminium, manganese, zinc, nickel, cobalt, thallium, vanadium, columbium, tantalum, and rare earths. 

Similarly, finely divided mixed metals undergo electrochemical reactions in contact with one another, sometimes with sufficient heat to ignite surrounding combustible materials or with a dangerous depletion of surrounding oxygen in confined spaces, o Lead dross (mostly lead sulphate) is acidic, o Arsenical flue dust and other metal by-products are toxic, o Residues may be mixed with other compounds and metals such as lead, cadmium, mercury, and uranium. 

Another process, developed at Molycorp, consists of the treatment of bastnaesite with HCl, yielding rare earth chlorides. These are subsequently treated with NaOH to convert them onto RE-hydroxides. After separation, are dissolved again in HCl, yielding rare earth chlorides. In the next step, the rare earth fluoride in the solid residue is converted to rare earth hydroxide using NaOH. Next follows neutralisation and purification. This involves hydrochloric acid, yielding a solution with a pH of about 3. By addition of hydroxide, iron precipitates as iron hydroxide. Sulphuric acid is used to precipitate lead sulphate. Then barium chloride is added to precipitate excess sulphate and to act as a carrier for the removal of any thorium daughter products present in the ore. At this pH, thorium hydroxide is insoluble and can be removed. Filtration finally leads to a clear solution of rare earth chlorides. This solution is then either concentrated by evaporation or by evaporation made into a solid form (Gupta and Krishnamurthy 2005). 

The sulphide leaching plant (SUP) receives feed from all of the fiont-end zinc plants roasters, ZPL, and OLP. This plant treats calcine, ZPL slurry, and OLP electrolyte using a weak acid and neutral leaching process to produce impure SLP electrolyte and residue. The residue consists mainly of zinc foiites, paragoethite, jarosites, lead sulphate, as well as coprecipitated impurities. The residue slurry is fed to the lead smelter. 

Lead sulphide is converted to insoluble lead sulphate. This together with silver, gold and insoluble gangue minerals (mostly silicates) will form a leach residue. The contamination of sulphate and silicate is likely to yield a residue of less than 30% Pb. Unless rich in silver, it is rarely attractive to treat at or transport from a mine location. 

Once the charge was made up to generate the calorific value desired, the opportunity was taken to compare the desulphurization rate of the charge to that of the lead-zinc concentrate charge. As expected, the duration of the desulphurization ]5rocess turned out to be nearly the same. If half of the lead-copper-zinc concentrate is substituted for lead sulphate middlings (for example, lead residue or lead dust), the desulphurization rate noticeably increases. This can be explained by the fact that the rate of the exchange reactions between sulphides and sulphates. 

In the case of sulphur present as lead sulphate, the treatment with lime (about the cheapest material suitable for this purpose) forming gypsum is preferred, which subsequently is removed by filtration. TR has developed techniques whereby pure gypsum can be produced in any of its three morphologies (hydrated, hemi-hydrated and anhydrous) to suit market demands. Therefore, the obtained gypsum residue could be converted to commercial gypsum products, if commercially feasible. The real benefit in this is not having to pay for its disposal. 

Sodium mlphanilate.—Burns with difficulty, leaving a residue of (chiefly) sodium sulphide. Add dil. HCl, and confirm without delay the evolution of HjS by means of a filter-pa per moistened with lead acetate solution. Typical of salts of the sulphonic acids. Acetone sodium bisulphite.—Almost non-inflammable, leaving a colourless residue of sodium sulphite and sulphate. Transfer residue to a test-tube, add dil. HCl, warm, and confirm the SO2 evolved. 

The presence of active sulphate-reducing bacteria usually results in graphitic corrosion and this has led to a useful method of diagnosing this cause of corrosion. The leaching out of iron from the graphitic residue which is responsible for the characteristic appearance of this type of corrosion leads to an enriched carbon, silicon and phosphorus content in the residue as compared with the original content of these elements in the cast iron. Sulphur is usually lost to some extent but when active sulphate-reducing bacteria are present, this loss is offset by the accumulation of ferrous sulphide in the residue with a consequent increase in the sulphur content of the residue out... 

Preparation. Industrially, cobalt is normally produced as a by-product from the production of copper, nickel and lead. The ore is roasted to form a mixture of metals and metal oxides. Treatment with sulphuric acid leaves metallic copper as a residue and dissolves out iron, cobalt and nickel as the sulphates. Iron is separated by precipitation with lime (CaO) while cobalt is produced as the hydroxide by precipitation with sodium hypochlorite. The trihydroxide Co(OH)3 is heated to form the oxide and then reduced with carbon (as charcoal) to form cobalt metal. 

The zinc sulphate produced in this process can be turned more easily to commercial account than iron sulphate. If to the solution of the zinc sulphate resulting from the process sodium carbonate or sodium hydrogen carbonate is added, a precipitate of hydrated zinc basic carbonate or zinc carbonate is obtained, which on ignition in a furnace yidds zinc oxide (commercially known as zinc white ), water, and carbon dioxide. Zinc white has a commercial value as a basis or body In paints it has one great advantage over white lead, which is used for the same purpose, in that it is far less poisonous. This method of treatment of the residual... 

Urea. 50 g of potassium cyanide is heated in an iron cmcible under a large flame until it begins to fuse. 140 g of red lead is added in small portions, while the mixture is stirred with a rod. When the addition is complete and the frothing has stopped, the fused mass is poured onto an iron tray. When cold, the mass is separated from metallic lead, ground up, and digested with 200 cc of cold water for 1 hour. The filtrate from this mixture is treated with 25 g of ammonium sulphate and evaporated to dryness on a water bath. The residue is powdered well, transferred to a flask and is boiled with 3 installments of ethanol under reflux, to dissolve the urea from the potassium sulphate. Each of the 3 ethanol extracts is filtered, then combined, and evaporated to a small bulk, until crystals of urea separate on cooling and standing. Mp 132°. 

The impurities in commercial carbonate may include ammonium thiosulphate derived from the. ammonium sulphate or ammonium chloride containing some sulphate ammonium sulphate or chloride, derived from the same sources lead, derived from leaden receivers and lime, calcium chloride, or other non-volatile substances may be present, and these remain as a permanent residue where the salt is volatilized. 

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