Lead chloride, precipitation

Masking may also be achieved by dissolving precipitates or by the selective dissolution of a precipitate from a mixture. Thus, when testing for lead in the presence of silver, we may produce a mixture of silver and lead chloride precipitates ... 

Introducing hydrogen sulphide gas into a mixture which contains white lead chloride precipitate, the latter is converted into (black) lead sulphide in a precipitate-exchange reaction ... 

Lead chloride precipitation Is hot quantitative for lead under normal conditions but can be useful for radiochemical purification of a lead fraction. It can also be used to remove the bulk of a large quantity of lead prior to more complete separations. Although sparingly soluble In cold water, lead, chloride (PbClg) Is readily soluble In hot water or In dilute, hot nitric add. This has been used as a separation from silver by precipitation of silver chloride from hot nitric add solutions (H3). Tlra (T1) reports that the condition for maximum yield of PbClg with hydrochloric add at 20 C occurs at pH 0.5... 

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. 

Suppose we have a solution that contains lead(II), mercury(I), silver, copper(II), and zinc ions. The method is outlined in Fig. 11.20, which includes additional cations, and is illustrated in Fig. 11.21. Most chlorides are soluble so, when hydrochloric acid is added to a mixture of salts, only certain chlorides precipitate (see Table 11.4). Silver and mercury(I) chlorides have such small values of Ksp that, even with low concentrations of Cl ions, the chlorides precipitate. Lead(II) chloride, which is slightly soluble, will precipitate if the chloride ion concentration is... 

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. 

Chemical precipitations which are not dependent on pH are used in various processes. Sometimes the reagent is reasonably set for a certain metal and this is the situation in the precipitation of silver as silver chloride. The only other insoluble common metal chlorides of significance are lead chloride, cuprous chloride, and mercurous chloride. This implies that precipitation of cuprous and mercurous chlorides generally may be avoided by ensuring that the metals occur in their higher oxidation states, cupric and mercuric states. The separation of silver in its chloride form is rarely employed for bulk precipitation, but is quite useful for removing relatively small amounts of the metal when it occurs in minor amounts. 

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). 

Admixture compatibility- Digoxin injection can be administered undiluted or diluted with a 4-fold or greater volume of sterile water for injection, 0.9% sodium chloride injection, or 5% dextrose injection. The use of less than 4-fold volume of diluent could lead to precipitation of the digoxin. Immediate use of the diluted product is recommended. 

The preferred preparation method is to introduce chlorine into the solution while dissolving lead dioxide in cold concentrated HCl. This prevents decomposition of PbCL to PbCb and enhances the formation of chloroplumbic acid, H2PbCl6 in solution. Addition of ammonium chloride precipitates out yellow ammonium chloroplumbate, (NH4)2PbCl6, which is filtered out. The yellow precipitate, on treatment with cold concentrated sulfuric acid, forms lead tetrachloride, which separates out as a yellow oily liquid. The reactions are ... 

Uranium mineral first is digested with hot nitric acid. AH uranium and radium compounds dissolve in the acid. The solution is filtered to separate insoluble residues. The acid extract is then treated with sulfate ions to separate radium sulfate, which is co-precipitated with the sulfates of barium, strontium, calcium, and lead. The precipitate is boiled in an aqueous solution of sodium chloride or sodium hydroxide to form water-soluble salts. The solution is filtered and the residue containing radium is washed with boiling water. This residue also contains sulfates of other alkahne earth metals. The sohd sulfate mixture of radium and other alkahne earth metals is fused with sodium carbonate to convert these metals into carbonates. Treatment with hydrochloric acid converts radium and other carbonates into chlorides, all of which are water-soluble. Radium is separated from this solution as its chloride salt by fractional crystallization. Much of the barium, chemically similar to radium, is removed at this stage. Final separation is carried out by treating radium chloride with hydrobromic acid and isolating the bromide by fractional crystallization. 

A) The reaction that produced the precipitate is Pb (a,) + 2C1 (aq) PbCl2(,). Lead chloride is a slightly soluble salt, with a solubility of 10 g/L at 20°C. The solubility of PbCF increases very rapidly as the temperature rises. At 100°C it has a solubility of 33.5 g/L. However, PbCl2 precipitates very slowly, particularly when other ions that form insoluble chlorides are not present. PbCb dissolves in excess chloride ion as a result of the formation of a complex ion, tetrachloroplumbate(II) ion ... 

N. A. E. Millon 4 found that when lead dioxide, Pb02, is added to well-cooled and cone, hydrochloric acid, but little chlorine is evolved, while lead chloride, PbCl2, and a yellow liquid are formed. The liquid slowly evolves chlorine and contains lead in soln. Lead dioxide is precipitated when water is added to the yellow liquid. It was therefore assumed that the liquid contains lead perchloride, PbCl4, in soln. and A. Guyard supposed that a soln. of iodine in potassium iodide contained potassium di-iodide, KI2, because this soln. gives lead tetraiodide, Pbl4, when treated with a lead salt. 

The chemical complexing-solvent extraction technique employed in this work involved the formation of a neutral complex in the aqueous phase between trialkyl lead chloride and a dithiocarbamate reagent such as sodium diethyl di-thiocarbamate. The complex was subsequently removed either as a precipitate or by extraction into an organic solvent. The extent of lead removal was traced by analysis of the aqueous phase for residual trialkyl lead using a Pye-Unicam 8000 spectrophotometer. 

The presence of alkali and alkaline earth chlorides may also hinder precipitation of the sulphide thus, from a 0001 molar solution of lead chloride in water at 20° C., precipitation is completely inhibited by hydrogen chloride alone if in a concentration of 1-riV, and by decreasing concentrations of the acid in the presence of increasing quantities of calcium, ammonium or potassium chloride. Cadmium sulphide, precipitated from hydrochloric acid solution, contains adsorbed chlorine,1 the amount depending on the conditions of the precipitation the precipitation is incomplete at 80° C. 

About lOg more of the product may be obtained from the mother liquor by heating it to 80°C and passing in a stream of dry chlorine until no more lead chloride forms. The mixture is filtered while hot and the residue is washed with 5-10ml of hot glacial acetic acid. On cooling, the lead tetraacetate precipitates. It is contaminated with a small amount of lead chloride. 

Decomposition is indicated when a fine precipitate of lead chloride begins to appear in the liquid. 

Aqueous solutions of calcium chloride, ferric chloride or silver nitrate give precipitates or colorations with certain organic acids which are valuable for the detection of these acids. It is important to use neutral solutions of the acids which at the same time do not contain metallic radicles likely to react with the reagents added. Thus the addition of calcium chloride to a solution of lead acetate may produce a precipitate of lead chloride. A neutral solution, which should be of about 10% concentration, prepared as follows, usually avoids such complications —... 

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