Aqueous solution precipitate

Fluorination with fluorine produces copper(ll) fluoride, CuF2. Adding potassium ferrocyanide to CuCb aqueous solution precipitates out reddish brown cupric ferrocyanide. Reaction with caustic soda forms blue cupric... 

In addition, at very low water contents, ampicillin accumulation curves do not exhibit a clear-cut maximum, inherent in the enzymatic acyl transfer reactions in aqueous medium (including quite concentrated heterogeneous aqueous solution-precipitate systems), because of the secondary hydrolysis of the target product by penicillin acylase (Figure 12.6) [84]. 

Caesium Tantalates.—Fusion of tantalum pentoxide with caesium carbonate and extraction with water yields monoclinic crystals of the 4 3 salt, 4Cs20.3Taa05.14H20 addition of alcohol to its aqueous solution precipitates the 7 6 salt, 7Cs20.6Ta205.38H20.4... 

The addition of phosphorus trichloride to an aqueous solution precipitates brown amorphous arsenic the reaction does not occur if the trichloride is first dissolved in water, nor when phosphorous acid is used.5 The reaction, which accords with the equation... 

Hydrolysis in aqueous solution precipitates hydrated titanium dioxide which, after washing and drying, can be calcined at 800°C to remove water and residual Cl. This method has been the basis of producing titanium dioxide of 99.999% purity. If retaining a high specific surface area is important, it may be convenient to reduce the residual Cl content by Sohxlet extraction rather than calcination. For many electroceramic uses, the millability of the product is as important as the absolute purity. A number of process variants designed to modify particulate morphology have been described (67). 

The double inverse microemulsion method was also used to synthesize per-ovskite-type mixed metal oxides [ 155]. One microemulsion solution contained nitrate salts of either Ba(N03)2/Pb(N03)2, La(N03)3/Cu(N03)2 or La(N03)3/ Ni(N03)2, and the other microemulsion contained ammonium oxalate or oxalic acid as the precipitant. These metal oxalate particles of about 20 nm were readily calcined into single phase perovskite-type BaPb03, La2Cu04 and LaNi03. The calcinations required for the microemulsion-derived mixed oxalates were 100-250 °C below the temperatures used for the metal oxalates prepared by a conventional aqueous solution precipitation method. 

Uranyl Thiocyanate, U02(CNS)2.8H30, may be obtained by the addition of barium thiocyanate to a solution of uranyl sulphate, and evaporation of the resulting red solution in a vacuum over sulphuric acid. It separates in orange-yellow needles, which are very hygroscopic and readily dissolve in water, alcohol, ether, and acetone ether may be used for extracting it from its aqueous solution. The addition of jyridine to its aqueous solution precipitates a crystalline basic salt of composition 5U02(CNS)2.U03. rH20. 

Naphthol (100 g., 0.70 mole) is dissolved in an aqueous solution containing 360 g. (6.3 moles) of potassium hydroxide. To this solution is added an aqueous solution of 95 g. (1.0 mole) of chloroacetic acid. Water is added to the mixture until a total volume of 2 1. is reached, and the resulting solution is stirred and heated on a water bath for 4 hours. The reaction mixture is treated with 100 ml. of concentrated hydrochloric acid and cooled the precipitated solid is filtered off, washed with water, and dried. There is obtained a 95 yield of crude product melting at 145-150 . The crude acid is treated with excess aqueous ammonium carbonate solution, and the resulting mixture is extracted with ether to remove the unreacted /8-naphthol. Acidification of the aqueous solution precipitates the yj-naphthoxy-acetic acid, which is collected by filtration and recrystallized from hot water to give white prisms melting at 156°. 

This arsenical is obtained by the Schotteii-Baumann reaction from benzene- n-disuIphonic chloride and Salvarsan. It is a yellow or yellowish-grey powder, yielding a yellowish-brown solution in sodium carbonate, but is insoluble in water. Addition of sodium chloride or alcohol to its aqueous solution precipitates the sodium salt, which has a neutral reaction in water and may be kept imchanged for several days if air is excluded. ... 

It crystallises in strongly refracting plates, easily soluble in water and exploding when heated. The addition, of a little dilute hydrocliloric add to the aqueous solution precipitates ethanol mercuric chloride. 

The production of catalyst particles of suitable configuration and hardness is an essential part of catalyst manufacture . Most heterogeneous catalysts are produced by processes that involve formation of solids from aqueous solutions. Precipitation is frequently employed in preparation of hydrous oxide catalysts. To avoid occluded or adsorbed impurities, ammonia or ammonium salts are often used as well as nitrates of the desired metal constituents. Calcination removes the nitrogen-containing components. Anions such as Cl or 864 or cations such as Na are avoided these often are poisons if they are present in the final catalyst. 

The strongly retained cations in soils include many of the essential microelements and also the toxic cations. The concentrations of these ions in the soil solution are low and they are apparently retained by two means. One group is the cations that in aqueous solutions precipitate as insoluble oxides and hydroxyoxides. The root zone of a typical agricultural soil might contain as much as 300 000 kg ha-1 of Fe and Al, but their plant availability is only a few kg ha-1. 

Youshko MI, van Langen LM, de Vroom E et al. (2000) Penicillin acylase-catalyzed synthesis of ampicilUn in aqueous solution-precipitate system. High substrate concentration and supersaturation effect. J Mol Catal B Enzym 10 509—515... 

Example 3.11 Polymerization of Acrylonitrile with a Redox System in Aqueous Solution (Precipitation Polymerization)... 

Two electrodes are immersed in aqueous sulfuric acid solution. One of the electrodes is zinc and the other one is copper. A barrier membrane is placed between the two electrodes. It could block the passage of cations, while it could allow anions to move through it freely. The copper is precipitated onto the zinc electrode. The color changes to dark brown, while the color of the solution (blue) gradually gets pale. This suggests that the copper ions in the aqueous solution precipitate onto the zinc electrode, as shown in Eq. (6). 

Three major t)q)es of chemical processes occur in aqueous solution precipitation reactions, acid-base reactions, and oxidation-reduction reactions. 

As we discussed in Chapter 7, many chemical reactions take place in aqueous solutions. Precipitation reactions, neutralization reactions, and gas evolution reactions, for example, all occur in aqueous solutions. Chapter 8 describes how we use the coefficients in chemical equations as conversion factors between moles of reactants and moles of products in stoichiometric calculations. These conversion factors are often used to determine, for example, the amount of product obtained in a chemical reaction based on a given amount of reactant or the amount of one reactant needed to completely react with a given amount of another reactant. The general solution map for these kinds of calculations is ... 

A solution of 1 mole of /i-butyllithium in 500 ml of ether is treated portionwise with 0.75 mole of fluorene. The solution turns an orange color accompanied by vigorous evolution of butane. The mixture is refluxed for 1 hr and then poured jetwise onto crushed dry ice. As soon as the mixture warms up to room temperature, the unreacted lithium is skimmed off and 2 liters of water is added cautiously. The insoluble residue is filtered off and the organic layer is extracted three times with 300-ml portions of luke-warm 2% sodium hydroxide. Acidification of the combined aqueous solutions precipitates the desired acid. The yield is 118 gm (75%), mp 228°-230°C, based upon fluorene. 

On heating, this compound begins to decompose at 225°C with evolution of gases smelling strongh of hydrogen cyanide. As in the case of formal-hydrazine, aqueous solutions precipitate formalazine on warming, a reaction which is accelerated by the presence of traces of acid. 

Alkvl and aralk -l aninioniuni dithiocarbamates, which are closelv re-lated to thioureas, react readily with fomialdehyde in aqueous solution, precipitating insoluble methylene derivatives ... 

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