Lead chloride solutions

Heats of precipitation have been employed to determine the enthalpies of sparingly soluble simple and complex fluorides for example, that of calcium fluoride by adding solid calcium chloride to a solution of excess sodium fluoride saturated with calcium fluoride (88), and of lead chlorofiuoride by adding sodium fluoride solution to a saturated lead chloride solution (50). 

Predictably, the formation of metal sulfides may occur at a site removed from that of bacterial sulfate reduction. Leleu and Goni (1974) used sulfate-reducing bacteria to provide hydrogen sulfide at a reasonably rapid rate to a lead chloride solution in an adjacent flask. Galena precipitated rapidly and produced dendritic and other incomplete forms such as found in some lead-zinc deposits. Similar experiments by Leleu et al. (1975) produced wurtzite. 

If apatite is treated with lead chloride solution, it forms pyromorphite (Chapter 5). This pyromor-phite (or lead orthophosphate) can then be reduced by hydrogen at comparatively low temperature... 

Tricalcium phosphate will react with lime to give hydroxyapatite (5.66). With lead chloride solution at room temperature, pyromorphite is obtained (5.67). 

Procedure. A drop of the hydrochloric acid test solution, a drop of a saturated solution of lead chloride, and 2 drops of stannite solution are stirred on a spot plate. In the presence of large amounts of bismuth, a precipitate of lead appears at once. Smaller amounts require 1-3 minutes before a definite brown appears, which gradually intensifies until the lead is completely precipitated. Since lead alone is also reduced, although slowly, a blank test with a drop of hydrochloric acid, lead chloride solution, and 2 drops of stannite solution should be carried out, if small amounts of bismuth are suspected. 

If a solution is too strongly acidic, especially with HCl (at least 1.4 M), either no precipitation of PbS with H2S takes place, or a red double compound, Pb2Cl2S, is formed incompletely. Chloride salts lower veiy distinctly the concentration of HCl necessary to prevent the precipitation of PbS from dilute lead chloride solution. 

In addition to the oxychlorides occurring as minerals, the two compounds Pb20Cl2 and Pb302Cl2 can be made in a number of ways, including the action of the requisite amount of alkali upon lead chloride solutions. Pb302Cl2 melts without decomposition at 693°C, and the heat of formation from PbCh and 2PbO is 9-24 kcal/mole. ... 

At pH 3.6-5.6, fluoride ions can be precipitated by a saturated lead chloride solution. The precipitate can be dried and weighed. 

Sodium sulfate is the main inorganic salt expected in sulfonated surfactants. It may also be deliberately added to formulations as a filler or processing aid. Classical methods for sulfate determination are gravimetric or based on BaCl2 titration. It has been found that non-aqueous acid-base titration permits sulfate to be differentiated from sulfonates (18). Sulfate ion has been titrated with lead chloride solution using dithizone as indicator and acetone/water as solvent (19). Alternatively, it may be titrated with barium perchlorate with Sulfonazo III as indicator (9). 

The solid is essentially ionic, made up of Pb and Cl ions. The vapour contains bent molecules of PbCh (cf. SnCh). Lead chloride is precipitated when hydrochloric acid (or a solution of a chloride) is added to a cold solution of a lead(ll) salt. It dissolves in hot water but on cooling, is slowly precipitated in crystalline form. It dissolves in excess of concentrated hydrochloric acid to give the acid H2[Pb"Cl4]. 

A precipitation reaction occurs when two or more soluble species combine to form an insoluble product that we call a precipitate. The most common precipitation reaction is a metathesis reaction, in which two soluble ionic compounds exchange parts. When a solution of lead nitrate is added to a solution of potassium chloride, for example, a precipitate of lead chloride forms. We usually write the balanced reaction as a net ionic equation, in which only the precipitate and those ions involved in the reaction are included. Thus, the precipitation of PbCl2 is written as... 

Lead Chloride. Lead dichloride, PbCl2, forms white, orthorhombic needles some physical properties are given in Table 1. Lead chloride is slightly soluble in dilute hydrochloric acid and ammonia and insoluble in alcohol. It is prepared by the reaction of lead monoxide or basic lead carbonate with hydrochloric acid, or by treating a solution of lead acetate with hydrochloric acid and allowing the precipitate to settle. It easily forms basic chlorides, such as PbCl Pb(OH)2 [15887-88 ] which is known as Pattinson s lead white, an artist s pigment. 

Qualitative. The classic method for the quaUtative determination of silver ia solution is precipitation as silver chloride with dilute nitric acid and chloride ion. The silver chloride can be differentiated from lead or mercurous chlorides, which also may precipitate, by the fact that lead chloride is soluble ia hot water but not ia ammonium hydroxide, whereas mercurous chloride turns black ia ammonium hydroxide. Silver chloride dissolves ia ammonium hydroxide because of the formation of soluble silver—ammonia complexes. A number of selective spot tests (24) iaclude reactions with /)-dimethy1amino-henz1idenerhodanine, ceric ammonium nitrate, or bromopyrogaHol red [16574-43-9]. Silver is detected by x-ray fluorescence and arc-emission spectrometry. Two sensitive arc-emission lines for silver occur at 328.1 and 338.3 nm. 

If aggregate is mixed with dry calcium chloride or a calcium chloride solution and then compacted, the presence of the calcium chloride draws ia moisture to biad the fine particles ia the aggregate matrix. This process leads to a well compacted, maximum deasity gravel road. This appHcatioa for calcium chloride was reviewed ia 1958 (27). More receat pubHcatioas are also available (28—30). 

Lead chloride is freely soluble in hot aqueous solutions, but lead fluoride is almost insoluble in dilute HE solutions. When the HE concentration reaches about 40%, steel is preferred. 

Fig. 1.45 Breakdown of oxide film leading to a pit and crack when a high-strength steel is subjected to a tensile stress in a chloride solution (after Brown )...

The predictions of the pH/potential diagram are generally fulfilled, but in very concentrated acid solutions, attack may diminish, owing to the relative insolubility of the relevant salt in the acid. Thus, lead nitrate, although soluble in water, has (owing to common ion effect) only slight solubility in concentrated nitric acid, and the corrosion rate is reduced. Similarly, lead chloride is less soluble in moderately concentrated hydrochloric acid than... 

The unequal attack which occurs in tap water, condensate and other mild electrolytes may lead to perforations of thin-gauge sheet and even to deep pitting of castings. In stronger electrolytes the effect is variable. In chloride solutions such as sea-water, attack on the metal usually results in the pitting of some areas only, but where the metal surface has been rendered reactive, as by shot blasting, attack may be so rapid that uniform dissolution over the whole surface may occur. In either case magnesium-base alloys are not usually suitable for use in aqueous liquids since they are not intrinsically resistant to these electrolytes. 

Feitknecht has examined the corrosion products of zinc in sodium chloride solutions in detail. The compound on the inactive areas was found to be mainly zinc oxide. When the concentration of sodium chloride was greater than 0-1 M, basic zinc chlorides were found on the corroded parts. At lower concentrations a loose powdery form of a crystalline zinc hydroxide appeared. A close examination of the corroded areas revealed craters which appeared to contain alternate layers and concentric rings of basic chlorides and hydroxides. Two basic zinc chlorides were identified, namely 6Zn(OH)2 -ZnClj and 4Zn(OH)2 ZnCl. These basic salts, and the crystalline zinc hydroxides, were found to have layer structures similar in general to the layer structure attributed to the basic zinc carbonate which forms dense adherent films and appears to play such an important role in the corrosion resistance of zinc against the atmosphere. The presence of different reaction products in the actual corroded areas leads to the view that, in addition to action between the major anodic and cathodic areas as a whole, there is also a local interaction between smaller anodic and cathodic elements. 

The insertion of platinum microelectrodes into the surface of lead and some lead alloys has been found to promote the formation of lead dioxide in chloride solutions" " . Experiments with silver and titanium microelectrodes have shown that these do not result in this improvement". Similar results to those when using platinum have been found with graphite and iridium, and although only a very small total surface area of microelectrodes is required to achieve benefit, the larger the ratio of platinum to lead surface, the faster the passivation". Platinised titanium microelectrodes have also been utilised. 

The formation of PbOj is favoured in solutions containing passivating anions such as SO4 and in chloride solutions of intermediate concentrations very high and very low concentrations of chloride inhibit the formation of Pb02- The platinum/lead bi-electrode performs best in seawater, and is not recommended for use in waters of high resistivity. 

If no depolariser is added to an acidic chloride solution, corrosion of the anode occurs and the dissolved platinum is deposited on the cathode, leading to erroneous results and to destruction of the anode. A number of metals (for example, zinc and bismuth) should not be deposited on a platinum surface. 

Pb2+ Tartrate buffer or chloride solution (solubility limits the amount of lead to less than 50 mg per 100 mL) 2 A 2-3 V... 

In a similar determination described by Lingane and Jones,11 an alloy containing copper, bismuth, lead, and tin is dissolved in hydrochloric acid as described above, and then 100 mL of sodium tartrate solution (0.1 M) is added, followed by sufficient sodium hydroxide solution (5M) to adjust the pH to 5.0. After the addition of hydrazinium chloride (4 g), the solution is warmed to 70 °C and then electrolysed. Copper is deposited at —0.3 volt, and then sequentially, bismuth at —0.4 volt, and lead at —0.6 volt all cathode potentials quoted are vs the S.C.E. After deposition of the lead, the solution is acidified with hydrochloric acid and the tin then deposited at a cathode potential of — 0.65 volt vs the S.C.E. 

Capillary tube isotachophoresis using a potential gradient detector is another technique that has been applied to the analysis of alcohol sulfates, such as sodium and lithium alcohol sulfates [303]. The leading electrolyte solution is a mixture of methyl cyanate and aqueous histidine buffer containing calcium chloride. The terminating electrolyte solution is an aqueous solution of sodium octanoate. 

The concentration of F ions can be measured by adding an excess of lead(II) chloride solution and weighing the lead(II) chlorofluoride (PbCIF) precipitate. Calculate the molarity of F ions in 25.00 mL of a solution that gave a lead chlorofluoride precipitate of mass 0.765 g. 

Re(VII), Mo(VI) and V(V) cations are detected by first spraying the chromatogram with tin(II) chloride solution (10% in 6 N hydrochloric acid) and then with ammonium thiocyanate solution (S0% in water). This leads to the formation of orange, pink or yellow-colored complexes [2]. 

Another way to obtain, under suitable conditions, stable dispersions of sur-factant-stabihzed nanoparticles consists in the direct suspension of some materials in w/o microemulsions. The formation of stable dispersions of rutile (size 80-450 mn) and carbon black (200-500 nm) in AOT// -xylene and of rutile, lead chloride, aluminium, antimony in solutions of calcium soaps in benzene has been reported [219,220],... 

Current flow at electrode surfaces often involves several simultaneous electrochemical reactions, which differ in character. For instance, upon cathodic polarization of an electrode in a mixed solution of lead and tin salt, lead and tin ions are discharged simultaneously, and from an acidic solution of zinc salt, zinc is deposited, and at the same time hydrogen is evolved. Upon anodic polarization of a nonconsumable electrode in chloride solution, oxygen and chlorine are evolved in parallel reactions. 

Where B = pyridine, piperidine or 1-methylimidazole, in methylene chloride solution, but under normal conditions rapid irreversible autoxidation takes place 232) leading to the formation of the well characterised 247, 248) fi-oxo product, (TPP)Fe(IlI)—0—Fe(III) (TPP) and since the rate of oxidation decreases 249, 250) with increasing excess of axial base, B, it follows 232, 251) that a five co-ordinate species, Fe(II) (Base)TPP, is probably involved as an intermediate which can then undergo a bimolecular termination reaction with Fe(II) (Base)02TPP, followed by autoxidation. Firstly 251),... 

Samples are hydrolyzed with hydrochloric acid and stannous chloride solution at elevated temperature, and the evolved carbon disulfide is drawn with an air steam through two gas washing tubes in series containing lead acetate and sodium hydroxide solutions and an absorption tube containing an ethanolic solution of cupric acetate and diethanolamine. Lead acetate and sodium hydroxide remove hydrogen sulfide and other impurities. In the absorption tube, the carbon disulfide forms two cupric complexes of Af,Af-bis(2-hydroxyethyl)dithiocarbamic acid with molecular ratios Cu CS2 of 1 1 and 1 2. These complexes are measured simultaneously by spectrophotometry at 453 nm. 

Sodium hydroxide, 10% in water. Dissolve 10 g of NaOH in 100 mL of distilled water Lead acetate, 30% in water. Dissolve 30 g of acetate in 100 mL of distilled water Stannous chloride solution. Dissolve 40 g of reagent in 100 mL of concentrated hydrochloric acid... 

As examples of some water-soluble salts, mention may be made of potassium chloride, copper sulfate, and sodium vanadate. As examples of some water-insoluble salts, mention may be made of some typical ones such as lead chloride, silver chloride, lead sulfate, and calcium sulfate. The solubilities of most salts increases with increasing temperature. Some salts possess solubilities that vary very little with temperature or even decline. An interesting example is provided by ferrous sulfate, the water solubility of which increases as temperature is raised from room temperature, remains fairly constant between 57 and 67 °C, and decreases at higher temperatures to below 12 g l-1 at 120 °C. Table 5.2 presents the different types of dissolution reactions in aqueous solutions, and Table 5.3 in an indicative way presents the wide and varied types of raw materials that different leaching systems treat. It will be relevant to have a look at Table 5.4 which captures some of the essential and desirable features for a successful leaching system. 

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