Lanthanum basic carbonate

The decompositions of the light lanthanide [81] oxalates (613 to 713 K), were generally similar to that described above for the lanthanum salt. The relative stabilities of these six salts, and also of the normal and basic carbonates, is Gd > Sm > Nd > La > Pr > Ce. With few exceptions, the intermediates (identified by composition and infi-ared measurements) were ... 

T. Curtius and A. Darapsky prepared a basic salt, lanthanum hydroxyazide, La(0H)(N3)2l H20, by boiling a soln. of lanthanum nitrate and sodium azide. The white, slimy mass of basic lanthanum azide is obtained by evaporating the mixed soln. in vacuo, or by treatment of the soln. with a mixture of alcohol and ether. They also made rose-coloured didymium hydroxyazide, Dy(OH)(N3)2, by evaporating a soln. of didymium carbonate in hydrazoic acid. Freshly precipitated yttrium hydroxide dissolves in hydrazoic acid, forming a soluble yttrium hydroxyazide boiling a soln. of yttrium sulphate and sodium azide gives a precipitate of yttrium hydroxide. L. M. Dennis found that zirconium hydroxide is precipitated when a soln. of zirconium salt is treated with potassium azide. 

Oxides of the type RjO arc formed by all rare earth elements, by the ignition of the hydroxide, nitrate, sulfate, carbonate, or oxalate. In general the basicity decreases with increase of atomic weight, though yttrium and scandium are exceptions to the rule. The basicity of lanthanum approaches that of the alkaline earths, while scandium is about as basic as aluminium. 

Cubic crystal, d 10.07. mp 1050°. (bp ca. 3300°). Actinium is more basic than lanthanum and is a strong electropositive element. Forms insol salts, e.g. carbonate, oxalate, etc. just as the lanthanides. 

The catalysts prepared with La surprisingly contained a higher amount of K than those prepared without La. We suggest that La enhances potassium uptake as the catalyst forms, because part of the La precipitates as a mixed potassium lanthanum carbonate, i.e. KLa(C03)2. A similar compound has been reported for sodium in the literature. A second important observauon is that the presence of both La and K in the catalyst does not necessarily induce a high selectivity, unless KOH is also employed in the basic I COs solution. Omission of KOH from the basic solution results in a similar chemical composition (compare cases two and four in Table 1.2) but a much less selective catalyst This is most likely a consequence of the precipitation procedure itself, tithout KOH in the base, a step-wise precipitation... 

Mosander discovered the new element in the following manner he transformed cerium (III) oxide into the carbonate, which he dissolved in nitric acid and evaporated to dryness. He pulverized the residue to a fine powder and treated it with cold dilute nitric acid, in which the more basic lanthanum oxide was dissolved, while cerium oxide remained undissolved. He then separated the lanthanum from... 

However, the limitation in CO adsorption, based on the availability of the active metal sites, results in severe accumulation of carbon deposits, which eventually deactivate the catalyst. In the presence of basic catalytic sites or basic supports such as La203, CO2 can easily be activated on basic sites, forming lanthanum... 

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