Calcium hydroxides, separator additives

The most common catalysts are sodium hydroxide and calcium hydroxide, generally used at a modest excess over the nominal stoichiometric amount to avoid formaldehyde-only addition reactions. Calcium hydroxide is cheaper than NaOH, but the latter yields a more facile reaction and separation of the product does not require initial precipitation and filtration of the metal formate (57). 

Lithium may be recovered from natural chloride brines. Such recovery processes may require additional steps depending on the magnesium and calcium content of the brine. The process involves evaporation of brine, followed by removal of sodium chloride and interferring ions such as calcium and magnesium. Calcium is removed by precipitation as sulfate while magnesium is removed by treating the solution with lime upon which insoluble magnesium hydroxide separates out. Addition of sodium carbonate to the filtrate solution precipitates hthium carbonate. 

The electrolysis Of fused alkali salts.—Many attempts have been made to prepare sodium directly by the electrolysis of the fused chloride, since that salt is by far the most abundant and the cheapest source of the metal. The high fusion temp. the strongly corrosive action of the molten chloride and the difficulty of separating the anodic and cathodic products, are the main difficulties which have been encountered in the production of sodium by the electrolysis of fused sodium chloride. Attention has been previously directed to C. E. Acker s process for the preparation of sodium, or rather a sodium-lead alloy, by the electrolysis of fused sodium chloride whereby sodium is produced at one electrode, and chlorine at the other but the process does not appear to have been commercially successful. In E. A. Ashcroft s abandoned process the fused chloride is electrolyzed in a double cell with a carbon anode, and a molten lead cathode. The molten lead-sodium alloy was transported to a second chamber, where it was made the anode in a bath of molten sodium hydroxide whereby sodium was deposited at the cathode. A. Matthiessen 12 electrolyzed a mixture of sodium chloride with half its weight of calcium chloride the addition of the chloride of the alkaline earth, said L. Grabau, hinders the formation of a subchloride. J. Stoerck recommended the addition of... 

Pentaerythritol.47 To a mixture of 18.5 g. of calcium hydroxide and 75 g. of formaldehyde in 500 cc. of water is slowly added 22 g. of acetaldehyde. The temperature of the mixture is maintained at 15° during the addition of the acetaldehyde and then gradually raised to 45°. The calcium is precipitated with oxalic acid, the calcium oxalate removed by filtration, and the filtrate evaporated to dryness under reduced pressure. The residue is taken up in 200 cc. of hot ethanol, and the resulting solution allowed to cool. The pentaerythritol which separates weighs 50 g. (73.5% of the theoretical amount) and melts at 258°. Pure pentaerythritol melts at 260°.46 ... 

The emission of sulphur oxides may be controlled by adding substances into the combustion chamber, which are able to bind sulphur dioxide (additive method). Finely group limestone, calcium hydroxide, calcium oxide or sometimes dolomite may be used for this purpose. Limestone is calcinated at high temperature, yielding calcium oxide, which binds the sulphur dioxide. Sulphate, sulphite, non-reacted adsorbent and fly ash are separated in a separating system. The disadvantage of this process is its low efficiency (only about 20 to 40% SO2 are retained). 

Chlorinating a slurry of lime in a sodium hydroxide solution forms crystals of calcium hypochlorite dihydrate, which can be filtered and dried. The precipitation of basic compounds is avoided by incremental addition of the calcium hydroxide to the sodium hydroxide solution during chlorination. In a batch process, all of the sodium hydroxide and 10-80% of the calcium hydroxide are introduced into a stirred reactor. Chlorine is then added. When the chlorination is nearly complete, the remainder of the calcium hydroxide is added without interrupting the flow of chlorine. The solids are separated and dried to from CalOCOj. In a continuous process, the sodium hydroxide solution is fed into one end of a long tubular reactor, and the calcium hydroxide slurry and chlorine are separately injected at a number of sites along the length of a jacketed reactor. The calcium hypochlorite is removed from the end of the reactor and dried. When impurities in the lime interfere with the crystallization of calcium hypochlorite, potassium hydroxide is substituted for up to 25% of the sodium hydroxide. ... 

After the addition of 2 1. of water, the mixture is steam-distilled as long as any oil comes over. The crude, heavy, yellow oil is separated and washed with two 200-cc. portions of 10 per cent sodium hydroxide, once with 100 cc. of water, twice with 150-cc. portions of concentrated sulfuric acid, and finally with 100 cc. of 5 per cent, sodium carbonate solution. It is dried with about 5 g. of calcium chloride, filtered through glass wool, and distilled using a long air condenser. Most of the product boils at i8o-i83°/75o mm. The yield of pure colorless material, b.p. i83°/76o mm., is 125-135 g. (36-39 per cent of the theoretical amount, based on the amount of -toluidine originally used, or 54-59 per cent based on the amount of 3-bromo-4-amino-toluene). 

H. 8-Hydroxyquinaldine (XI). The reactions of 8-hydroxyquinaldine are, in general, similar to 8-hydroxyquinoline described under (C) above, but unlike the latter it does not produce an insoluble complex with aluminium. In acetic acid-acetate solution precipitates are formed with bismuth, cadmium, copper, iron(II) and iron(III), chromium, manganese, nickel, silver, zinc, titanium (Ti02 + ), molybdate, tungstate, and vanadate. The same ions are precipitated in ammoniacal solution with the exception of molybdate, tungstate, and vanadate, but with the addition of lead, calcium, strontium, and magnesium aluminium is not precipitated, but tartrate must be added to prevent the separation of aluminium hydroxide. 

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