Hydroxides, molten

When chlorine is passed over molten sodium or potassium hydroxide, oxygen is evolved, the high temperature causing the chlorate V) ion to decompose ... 

Assemble the apparatus shown in Fig. 1 V, 67, 1 this is self-explanatory. The distilling flask has a capacity of 250 ml. and the beaker contains 150 ml. of 10 per cent, sodium hydroxide solution. All corks must fit well and should be coated with paraflSn wax (by dipping into molten wax, and allowing to drain). Place half of the yield of the dry phenyldiazonium fluoborate in the distilling flask. Heat the solid gently with a small luminous flame at one point near its surface until decomposition begins withdraw the flame and allow the reaction to continue... 

Chemica.1 Properties. The FEP resin is inert to most chemicals and solvents, even at elevated temperatures and pressures. However, it reacts with fluorine, molten alkah metal, and molten sodium hydroxide. Acids or bases are not absorbed at 200°C and exposures of one year. The absorption of organic solvents is less than 1% at elevated temperatures and long exposure times. Absorption of chemicals or solvents has no effect on the chemical integrity of the FEP molecule and is a reversible physical process. 

Lithium is used in metallurgical operations for degassing and impurity removal (see Metallurgy). In copper (qv) refining, lithium metal reacts with hydrogen to form lithium hydride which subsequendy reacts, along with further lithium metal, with cuprous oxide to form copper and lithium hydroxide and lithium oxide. The lithium salts are then removed from the surface of the molten copper. 

Lithium Chloride. Lithium chloride [7447- 1-8], LiCl, is produced from the reaction of Hthium carbonate or hydroxide with hydrochloric acid. The salt melts at 608°C and bods at 1382°C. The 41-mol % LiCl—59-mol % KCl eutectic (melting point, 352°C) is employed as the electrolyte in the molten salt electrolysis production of Hthium metal. It is also used, often with other alkaH haHdes, in brazing flux eutectics and other molten salt appHcations such as electrolytes for high temperature Hthium batteries. 

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Molten magnesium chloride can be formed by the direct carbochlofination of magnesium oxide obtained from the calciaation of magnesium carbonate ores or magnesium hydroxide [1309-42-8]. 

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

Naphthalenediol. This diol is made by the fusion of sodium 2,7-naphthalenedisulfonate with molten sodium hydroxide at 280—300°C in ca 80% yield. A formaldehyde resin prepared from this diol has excellent erosion resistance, strength, and chemical inertness it is used as an ablative material in rocket-exhaust environments (76). 

In the alkaline process, an aqueous solution of sodium hydroxide is allowed to react with molten, yellow phosphoms. A long-chain alcohol is used as a dispersant (3). The reaction to produce phosphine may be represented by equation 1. 

Molten aluminum reacts violently with water [7732-18-5] and the molten metal should not be allowed to touch damp tools or containers. In finely divided powder form, aluminum also reacts with boiling water to form hydrogen and aluminum hydroxide [21645-51 -2], this reaction proceeds slowly in cold water. 

Gas-phase oxidation of propylene using oxygen in the presence of a molten nitrate salt such as sodium nitrate, potassium nitrate, or lithium nitrate and a co-catalyst such as sodium hydroxide results in propylene oxide selectivities greater than 50%. The principal by-products are acetaldehyde, carbon monoxide, carbon dioxide, and acrolein (206—207). This same catalyst system oxidizes propane to propylene oxide and a host of other by-products (208). 

Sulfur combines directly with hydrogen at 150—200°C to form hydrogen sulfide. Molten sulfur reacts with hydrogen to form hydrogen polysulfides. At red heat, sulfur and carbon unite to form carbon disulfide. This is a commercially important reaction in Europe, although natural gas is used to produce carbon disulfide in the United States. In aqueous solutions of alkaU carbonates and alkaU and alkaline-earth hydroxides, sulfur reacts to form sulfides, polysulfides, thiosulfates, and sulfites. 

If tin and sulfur are heated, a vigorous reaction takes place with the formation of tin sulfides. At 100—400°C, hydrogen sulfide reacts with tin, forming stannous sulfide however, at ordinary temperatures no reaction occurs. Stannous sulfide also forms from the reaction of tin with an aqueous solution of sulfur dioxide. Molten tin reacts with phosphoms, forming a phosphide. Aqueous solutions of the hydroxides and carbonates of sodium and potassium, especially when warm, attack tin. Stannates are produced by the action of strong sodium hydroxide and potassium hydroxide solutions on tin. Oxidizing agents, eg, sodium or potassium nitrate or nitrite, are used to prevent the formation of stannites and to promote the reactions. 

The reactivity of titanium dioxide toward acid is dependent on the temperature to which it has been heated. Freshly precipitated titanium dioxide is soluble iu concentrated hydrochloric acid. However, titanium dioxide that has been heated to 900°C is almost iusoluble iu acids except hot concentrated sulfuric, iu which the solubiUty may be further iucreased by the addition of ammonium sulfate to raise the boiling poiut of the acid, and hydrofluoric acid. Similarly, titanium dioxide that has been calciued at 900°C is almost iusoluble iu aqueous alkahes but dissolves iu molten sodium or potassium hydroxide, carbouates, or borates. 

Zirconium is not attacked by caustics up to boiling temperatures. It is resistant to molten sodium hydroxide to 1000°C, but is less resistant to potassium hydroxide. 

CP can also be prepared by the reaction of cellulose with phosphoms oxychloride in pyridine (37) or ether in the presence of sodium hydroxide (38). For the most part these methods yield insoluble, cross-linked, CP with a low DS. A newer method based on reaction of cellulose with molten urea—H PO is claimed to give water soluble CP (39). The action of H PO and P2 5 cellulose in an alcohol diluent gives a stable, water-soluble CP with a high DS (>5% P) (40). These esters are dame resistant and have viscosities up to 6000 mPa-s(=cP) in 5 wt % solution. Cellulose dissolved in mixtures of DMF—N2O4 can be treated with PCl to give cellulose phosphite [37264-91-8] (41) containing 11.5% P and only 0.8% Cl. Cellulose phosphinate [67357-37-5] and cellulose phosphonate [37264-91 -8] h.a.ve been prepared (42). 

Molten (177—343°C) cesium hydroxide can be used in desulfurizing heavy oils. The hydroxide may be recycled by steam hydrolysis (55). 

More recendy, the molten caustic leaching (MCL) process developed by TRW, Inc. has received attention (28,31,32). This process is illustrated in Eigure 6. A coal is fed to a rotary kiln to convert both the mineral matter and the sulfur into water- or acid-soluble compounds. The coal cake discharged from the kiln is washed first with water and then with dilute sulfuric acid solution countercurrendy. The efduent is treated with lime to precipitate out calcium sulfate, iron hydroxide, and sodium—iron hydroxy sulfate. The MCL process can typically produce ultraclean coal having 0.4 to 0.7% sulfur, 0.1 to 0.65% ash, and 25.5 to 14.8 MJ/kg (6100—3500 kcal/kg) from a high sulfur, ie, 4 wt % sulfur and ca 11 wt % ash, coal. The moisture content of the product coal varies from 10 to 50%. 

Reaction of benzenesulfonic acid with sodium hydroxide This is the oldest method for the preparation of phenol. Benzene is sulfonated and the benzenesulfonic acid heated with molten sodium hydroxide. Acidification of the reaction mixture gives phenol. 

SiC has greater thermal stability than any other binary compound of Si and decomposition by loss of Si only becomes appreciable at 2700°. It resists attack by most aqueous acids (including HE but not H3PO4) and is oxidized in air only above 1000° because of the protective layer of Si02 this can be removed by molten hydroxides or carbonates and oxidation is much more rapid under these conditions, e.g. ... 

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