Lanthanum compared with

Some nut trees accumulate mineral elements. Hickory nut is notable as an accumulator of aluminum compounds (30) the ash of its leaves contains up to 37.5% of AI2O2, compared with only 0.032% of aluminum oxide in the ash of the Fnglish walnut s autumn leaves. As an accumulator of rare-earth elements, hickory greatly exceeds all other plants their leaves show up to 2296 ppm of rare earths (scandium, yttrium, lanthanum, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). The amounts of rare-earth elements found in parts of the hickory nut are kernels, at 5 ppm shells, at 7 ppm and shucks, at 17 ppm. The kernel of the Bra2d nut contains large amounts of barium in an insoluble form when the nut is eaten, barium dissolves in the hydrochloric acid of the stomach. 

ZnO photocatalyst can also be coupled with other materials in order to improve its chemical and physical properties [183] and photocatalytic activity [184]. Nanosized ZnO was immobilized on aluminum foil for the degradation of phenol [185]. Lanthanum and ZnO were combined to degrade 2,4,6-trichlorophenol [186]. Compared with Ti02 nanomaterial, ZnO nanomaterial generally absorbs a significant amount of the solar spectrum in the visible range therefore, ZnO nanomaterials were combined with Ti02 nanomaterials used as a photocatalyst [187]. 

Enthalpies of solution of lanthanum (180) and scandium (208) trichlorides in 14.1% and in 0.5 M aqueous hydrochloric acid, respectively, are also smaller than the respective enthalpies of solution in water. In the former case the values - 26.4 and — 31.6 kcal mol-1 were measured at 20°C in the latter, a value of — 43.0 kcal mol-1 for dissolution in hydrochloric acid at 25°C has to be compared with a value of -47.1 kcal mol-1 for dissolution in water at 20°C (180). Enthalpies of... 

An extreme example of the measurement of solution enthalpies is provided by that of lanthanum trichloride in molten potassium chloride. The value reported, which refers to infinite dilution, is - 20.8 kcal mol-1 (-87.0 kJ mol-1), at 890°C (223). This value is comparable with those for dissolution in lower alcohols at normal temperatures. 

Of a series of powdered refractory compounds examined, only lanthanum hexa-boride, hafnium carbide, titanium carbide, zirconium carbide, magnesium nitride, zirconium nitride and tin(II) sulfide were dust explosion hazardous, the 2 latter being comparable with metal dusts. Individual entries are ... 

Of those factors that have proved a disincentive to the wider application of the metals perhaps none has proved more formidable than cost. Unquestionably some rare earth metals are expensive when compared with many of the more common metals but then others, such as the commercial grades of lanthanum and cerium produced by electrolytic methods, are relatively inexpensive. Unfortunately, for most rare earth metals one must use a metallothermic reduction process that is inherently costly to operate. However, while there is a wide variation in the price of the various metals, from 50 - 7,000 per lb., the overall picture is one of relative price stability when judged against the movements of many other metals. To some extent this stability has been born out of the need to encourage potential users to adopt a particular metal in the face of a competitive product while in other cases it reflects more the economy of scale that has been possible once production has passed a given level. 

C. Find [La33 ] in the solution when excess solid lanthanum iodate, La(I03), is stirred with 0.050 M LiI03 until the system reaches equilibrium. Assume that I03 from La(I03)3 is negligible compared with I03 from LiI03. 

Comparison of Figures 2, 4, and 5 and Table II shows that the decreases in cracking activity and acidity can be correlated with the loss in crystallinity. The destruction of the framework occurs in a narrower, upper range of temperature for the lanthanum samples as compared with the parent materials. 

If the values of the parameters used in the calculation are compared, the determining factor is the much lower value of I4 for cerium (3547 kJ/mol compared with 4819 kJ/mol for La) due to the fact that the fourth electron is being removed from a different shell (nearer the nucleus) in the case of lanthanum. 

As a result of these factors, the REE pattern of seawater is distinctive. The seawater pattern is heavy REE enriched (e.g., Elderfield and Greaves, 1982). In addition, cerium shows a marked depletion compared with its neighbors, lanthanum and praseodymium. Because average shale contains a negative europium anomaly compared to chondrites, the practice of normalizing seawater to... 

Fig. 11. The protective action of 0.5% lanthanum chloride on atomic absorption of 1 mg % calcium against the depressive effect of phosphate. Compare with Fig. 4 (from reference (Z3) by permission).

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