Alkali Dioxides

In the method of Stephanou, Schlechter, Argersinger and Klein-berg, 92% pure NagO is prepared by the action of Og on NagOg at 

According to Klemm and Sodomann, as well as Helms and Klemm, the best method for preparing KOa, RbOa and CsOa is by oxidation of the elements, dissolved in liquid NH3, with Oa at -30 to -50 t . Intermediate products appear first. Their color is light yellow when fresh, then dark. Finally, yellow dioxides are formed. To prevent an explosion, which is common in this reaction. Lux 

Yellow substances, decomposed by HaO with evolution of Oa. The structure of NaOa is similar to that of NaCl, with Oa replacing the Cl ions. Structures of KOa, RbOa and CsOa CaCg lattice (Cll). 

To prepare lithium hydroxide by the method of Barnes, equivalent amounts of aqueous solutions of LiaSO andBa(OH)a are 

According to De Forcrand, the powdered monohydrate is converted to LiOH on drying for several days over PaO 5 in vacuum. The dehydration can also be accomplished by slow heating of the monohydrate of 140°C in a silver boat, white in a stream of pure Ha. If the temperature is raised too rapidly, the preparation melts at 445°C and converts to a hydrate 8LiOH HaO, which can be dehydrated only with difficulty. At 660-780°C the compoimd loses all its water and LiaO remains as a residue. 

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HM 7—7.5) White, translucent, hard caramic material. Readily soluble in HF Titanium and in concentrated H2SO4, and reacts rapidly with molten alkali dioxide hydroxides and fused alkali carbonates. Owing to its good corrosion (rutile, resistance to liquid metals such as Ni and Mo, it is used in crucibles titania) for melting these metals. Titania is readily attacked unds an inert atmosphere by molten metals such as Be, Si, Ti, Zr, Nb, and Ta,... 

Titanium IV) oxide, T1O2. See titanium dioxide. Dissolves in concentrated alkali hydroxides to give titanates. Mixed metal oxides, many of commercial importance, are formed by TiOj. CaTiOj is perovskite. BaTiOa, per-ovskite related structure, is piezoelectric and is used in transducers in ultrasonic apparatus and gramophone pickups and also as a polishing compound. Other mixed oxides have the il-menite structure (e.g. FeTiOj) and the spinel structure (e.g. MgjTiO ). 

Vanadium dioxide, VO2 is dark blue (V2O5 plus SO2) but is readily reduced further to Vo.i86-V,.6a. VO2 gives the (VO) ion with acids and vanadates(IV) with alkalis and as mixed metal oxides. 

As with the hydroxides, we find that whilst the carbonates of most metals are insoluble, those of alkali metals are soluble, so that they provide a good source of the carbonate ion COf in solution the alkali metal carbonates, except that of lithium, are stable to heat. Group II carbonates are generally insoluble in water and less stable to heat, losing carbon dioxide reversibly at high temperatures. 

Chemically, carbon dioxide is not very reactive, and it is often used as an inactive gas to replace air when the latter might interact with a substance, for example in the preparation of chromium II) salts (p. 383). Very reactive metals, for example the alkali metals and magnesium can, however, continue to bum in carbon dioxide if heated sufficiently, for example... 

Lead dioxide is slightly soluble in concentrated nitric acid and concentrated sulphuric acid, and it dissolves in fused alkalis. It therefore has amphoteric properties, although these are not well characteri.sed since it is relatively inert. 

If this reaction takes place in air, the evolved nitrogen monoxide is oxidised to the dioxide and this dissolves again as in equation (9.1) hence virtually complete conversion of nitrogen dioxide to nitric acid can occur (see nitric acid, below). With alkalis, a mixture of nitrite and nitrate is formed ... 

Sulphur dioxide is an acidic oxide and dissolves readily in water, and in alkalis with which it forms salts ... 

Alternatively these salts can be prepared by first saturating a known volume of alkali with sulphur dioxide, giving a solution of the hydrogensulphite, from which sulphite can be prepared by the addition of a second equal volume of alkali. 

Tellurium dioxide, Te02, is a white non-volatile solid obtained when tellurium is burnt in air. It is only slightly soluble in water but dissolves in alkalis to form salts. 

Only chloric(III) acid, HCIO2, is definitely known to exist. It is formed as one of the products of the reaction of water with chlorine dioxide (see above). Its salts, for example NaClOj, are formed together with chlorates)V) by the action of chlorine dioxide on alkalis. Sodium chlorate(III) alone may be obtained by mixing aqueous solutions of sodium peroxide and chlorine dioxide ... 

It must be kept under an atmosphere of nitrogen or carbon dioxide it reduces, for example, Fe(III) to Fe(II) and nitro-organic compounds RNO2 to amines RNH2 (it may be used quantitatively to estimate nitro-compounds). In neutral solution, hydrolysis occurs to give species such as [Ti(0H)(H20)s], and with alkali an insoluble substance formulated as Ti203 aq is produced this is rapidly oxidised in air. 

It is extensively used industrially as a catalyst, notably in the oxidation of sulphur dioxide to the trioxide in sulphuric acid manufacture. It is an essentially acidic oxide, dissolving in alkalis to give vanadates however, addition of acid converts the anionic vanadate species to cationic species, by processes which are very complex, but which overall amount to the following ... 

Ketonic Hydrolysis. Hot dilute caustic alkalis or hydrochloric acid first hydrolyse off the ethyl group, and then remove carbon dioxide, a mono- or di-substituted acetone being thus obtained ... 

The process may now be continued. Methylarsonic acid, when reduced by sulphur dioxide in concentrated hydrochloric acid, gives dichloromethylarsine, CHjAsCl. If this arsine is added to aqueous sodium hydroxide, it is hydrolysed to the weakly acidic methylarsenous acid, CH3As(OH)j, which in the alkali... 

Once the presence of a sulphonate group has been estabhshed (and, if possible, the phenol isolated), the compound may be characterised by the preparation of a derivative. It must be remembered that both sulphoxides RSOR and sulpJiones RSOjR yield sulphur dioxide on fusion with caustic alkali and acidification. 

Alkali metals Moisture, acetylene, metal halides, ammonium salts, oxygen and oxidizing agents, halogens, carbon tetrachloride, carbon, carbon dioxide, carbon disul-flde, chloroform, chlorinated hydrocarbons, ethylene oxide, boric acid, sulfur, tellurium... 

Sulfuryl dichloride Alkalis, diethyl ether, dimethylsulfoxide, dinitrogen tetroxide, lead dioxide, phosphorus... 

Sodium bicarbonate may be prepared by the ammonia-salt (Solvay) process. Carbon dioxide is passed through a solution of sodium chloride in ammonia water. Sodium bicarbonate is precipitated and the ammonium chloride remains in solution. The ammonium chloride is heated with lime to regenerate ammonia (see Alkali AND CHLORINE PRODUCTS). 

Lead nitrate [10099-74-8] Pb(N02)2, mol wt 331.23, sp gr 4.53, forms cubic or monoclinic colorless crystals. Above 205°C, oxygen and nitrogen dioxide are driven off, and basic lead nitrates are formed. Above 470°C, lead nitrate is decomposed to lead monoxide and Pb O. Lead nitrate is highly soluble in water (56.5 g/100 mL at 20°C 127 g/100 mL at 100°C), soluble in alkalies and ammonia, and fairly soluble in alcohol (8.77 g/100 mL of 43% aqueous ethanol at 22°C). Lead nitrate is readily obtained by dissolving metallic lead, lead monoxide, or lead carbonate in dilute nitric acid. Excess acid prevents the formation of basic nitrates, and the desired lead nitrate can be crystallized by evaporation. 

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