Chlorides precipitation

Addition of barium chloride precipitates white barium sulphite ... 

Lithium chlorate [13453-71 -9] LiClO, has rhombic needles mp 124—129°C decomposes on heating to 270°C. It is one of the most soluble salts known and it is very hygroscopic. LiClO is prepared by adding lithium chloride [7447-41-8] to sodium chlorate solution. Sodium chloride precipitates, the hquor is concentrated, and the lithium chlorate is filtered and dried. It has limited use in pyrotechnics. 

The reaction of lithium with methyl chloride in ether solution produces a solution of methyllithium from which most of the relatively insoluble lithium chloride precipitates. Ethereal solutions of halide-free" methyllithium, containing 2-5 mole percent of lithium chloride, were formerly marketed by Foote Mineral Company and by Lithium Corporation of America, Inc., but this product has been discontinued by both companies. Comparable solutions are also marketed by Alfa Products and by Aldrich Chemical Company these solutions have a limited shelf-life and older solutions have often deteriorated... 

Iron(III) nitrate is soluble, but silver chloride is not When these two solutions are mixed, silver chloride precipitates. 

The negative voltage shows that the state of equilibrium favors the reactants more than the products for the reaction as written. For standard conditions, the reaction will not tend to occur spontaneously. However, if we place Ag(s) in 1 M H+, the Ag+ concentration is not 1 M— it is zero. By Le Chatelier s Principle, this increases the tendency to form products, in opposition to our prediction of no reaction. Some silver will dissolve, though only a minute amount because silver metal releases electrons so reluctantly compared with H2. It is such a small amount, in fact, that no silver chloride precipitate forms, even though silver chloride has a very low solubility. 

A complete ionic equation for a precipitation reaction shows all the dissolved ions explicitly. For example, the complete ionic equation for the silver chloride precipitation reaction shown in Fig. 1.5 is... 

FIGURE 1.5 (a) Silver chloride precipitates immediately when sodium chloride solution is added to a solution of silver nitrate, (b) If we imagine the removal of the spectator ions from the complete ionic reaction (top), we can focus on the essential process, the net ionic reaction (bottom). 

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... 

FIGURE 11.22 When ammonia is added to a silver chloride precipitate, the precipitate dissolves. However, when ammonia is added to a precipitate of mercury(l) chloride, mercury metal and mercury(ll) ions are formed in a redox reaction and the mass turns gray. Left to right silver chloride in water, silver chloride in aqueous ammonia, mercury(l) chloride in water, and mercury(l) chloride in aqueous ammonia. 

The potassium chloride precipitates from the solution shifting the equilibrium to the right side. On heating to 100 °C this NaaSs sample decomposed exothermically to a 1 1 mixture of NaaSa and Na2S4 similar to the one described above. 

A second method which is now probably the most widely used method in the Pediatric Laboratory is to use amperometric titration. In this connection, a constant current flows through the solution. The silver dissolves and reacts stolchlometrlcally with chloride, precipitating silver chloride. When all of the chloride has reacted, there is a sharp increase in conductivity which is read as an end point. This instrument, therefore, measures the amount of time a current flows. Instruments are now available for which 5 microliters can be used routinely, rapidly, titration being of the order of about 20 seconds. 

Acyl chlorides can be prepared by direct acylation of hydrogen chloride with imidazo-lides. If two moles of hydrogen chloride are passed into a solution containing one mole of an imidazolide in a solvent in which the imidazolium chloride is insoluble (e.g., chloroform, dichloroethane), the imidazolium chloride precipitates and the acyl chloride is formed in excellent yield and a high degree of purity. Examples are provided in Table 13-2. ... 

Syntheses. Isotactic poly(methyl methacrylate) was synthesized by the method of Tsuruta et al. (9 ). Under a nitrogen atmosphere, a quantity of 6 mL (0.056 mole) of methyl methacrylate (MMA) dried over 4A molecular sieve was dissolved in 24 mL of similarly dried toluene. To the glass vial containing the reaction was added 0.65 mL of 1.6 M n-butyllithium, and the reaction was kept at -78°C in a dry ice/isopropanol bath. The polymerization was halted 24 hr later with the addition of hydrochloric acid and methanol (methanol/water 4.1 by volume). The polymer was dried in vacuo at 50°C, redissolved in methylene chloride, precipitated by being poured into water-containing methanol, and dried in vacuo at 50°C. Tacticlty and composition were verified with % NMR. Yield 47%. 

The apparatus shown in Fig. 16 is set up in the fume hood. The equipment is flushed with dry nitrogen, then a 200-ml. portion (314.8 g., 2.29 mols) of phosphorus trichloride is placed in the 2-1. reaction flask. The flask is partially immersed in the Dry Ice-isopropyl alcohol bath the clamp to the alkylamine container is opened and a stream of dry nitrogen is passed through the system at a rate of about 30 cc./minute measured at S.T.P. The nitrogen stream sweeps the anhydrous amine (200 g.) from the bottle into the reactor. The amine usually condenses on one of the two cold fingers of the reactor and drips into the chilled stirred phosphorus trichloride solution. Finely divided dimethylammonium chloride precipitates immediately. 

Clandot A process for extracting silver from its ores by extracting with aqueous ferric chloride, precipitating silver iodide by adding zinc iodide, and then reducing the iodide to the metal by heating with zinc. Used in the late 19th century. 

Pechiney H+ A process for extracting aluminum from clays and other aluminous ores and wastes by hydrochloric acid. The ore is first attacked by sulfuric acid and a hydrated aluminum chloride sulfate is isolated. Sparging a solution of this with hydrogen chloride precipitates aluminum trichloride hexahydrate, which is pyrohydrolyzed in two stages. Invented in 1977 by J. Cohen and A. Adjemian at Aluminium Pechiney, France, and subsequently developed in association with Alcan. Piloted in France but not yet commercialized. 

A large quantity of sodium chloride precipitates during addition of the epichlorohydrin. 

For the filtration use a small filter tube with a fritted glass filter (cf. Fig. 41). Pour into the filter a suspension of finest asbestos (for Gooch crucibles) to form a layer 2-3 mm. thick after sucking dry at the pump. Before using the filter tube, pour in a little silver chloride precipitated in the cold. As soon as the filtrate is clear the tube is ready for use. 

A sample is tested for the presence of the Hg22+ ion. This ion, along with others, may be precipitated with chloride ion. If Hg22+ is present in the chloride precipitate, a black color will form upon treatment with aqueous ammonia. The balanced net ionic equation for the formation of this black color is ... 

Once the two salts are mixed in solution (acetone is a common solvent for this), the sodium chloride precipitates and is removed by filtration. The solvent is then removed under reduced pressure and, since salts have no vapour pressure, the ionic liquid remains in the flask. The problem with this reaction is that it is almost impossible to remove the last traces of chloride ions. The chloride not only influences the physical properties of the liquid such as melting point and viscosity, but is also a good nucleophile and can deactivate catalysts and affect reproducibility. A great deal of effort has been directed towards removal of the chloride contamination, including washes and chromatography, but none have proved to be completely effective [9], This has led to the development of some alternative synthetic routes. Simply exchanging Na[BF4]... 

Caustic washing and thermal treatment of silver chloride precipitate are performed to achieve a 5X decontamination level for shipment to an offsite silver recovery operation. 

Will silver chloride precipitate under the given conditions ... 

Hersh emd coworkers (16,41) used energy dispersive X-ray spectroscopy to identify potassium chloride precipitates from water extracts of bracts. They also identified sodium, magnesium, aluminum, silicon, iron and copper in dried aqueous extracts of bracts. No quantitative malyses were made. 

To obtain MSMA, the DSMA solution is partially acidified with sulfuric acid and the resulting solution concentrated by evaporation. As the aqueous solution is being concentrated, a mixture of sodium sulfate and sodium chloride precipitates out (about 0.5 kg per 100 kg of active ingredient). These salts are a troublesome disposal problem because they are contaminated with arsenic. The salts are removed by centrifugation, washed in a multistage, countercurrent washing cycle, and then disposed of in an approved landfill. 

Copious amounts of potassium chloride precipitate during this addition. It is not necessary to remove the salt by filtration before the ether extraction. 

Thionyl chloride nitrate and thionyl nitrate are prepared in situ from the reaction of a solution of thionyl chloride in THF with one and two equivalents of silver nitrate respectively, during which time silver chloride precipitates from solution. ... 

Lithium chloride precipitates during the warm-up procedure. 

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