Cerium magnesium nitrat

In such experiments information about the phonons is deduced by measurements on the spin system. With the advent of monochromatic laser sources, the technique of Brillouin scattering can be used to track phonons of definite momentum and polarization, together with the number of such phonons. Al tshuler et al. (1971, 1972) used a helium-neon laser in experiments on cerium magnesium nitrate at... 

After removing cerium (and thorium), the nitric acid solution of rare earths is treated with ammonium nitrate. Lanthanum forms the least soluble double salt with ammonium nitrate, which may be removed from tbe solution by repeated crystallization. Neodymium is recovered from this solution as the double magnesium nitrate by continued fractionation. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Cement, laboratory, 1 189 Cerite, extraction of, 2 44 Cerium, phosphor containing strontium sulfide and, 3 23 separation of, from rare earth mixtures, 2 43, 47, 48 test for, 2 50 Cerium amalgam, 1 15 Cerium-group earths, separation of, from yttrium earths by doublesulfate method, 2 44, 46 Cerium (III) magnesium nitrate, 2Ce(N03)s-3Mg(N03)2-24H,0, separation of praseodymium from lanthanum by, 2 57 Cerium(III) nitrate, 2 51 Cerium (IV) nitrate, basic, 2 49 Cesium, cesium azide for preparation of, 1 79... 

Magnesium cerium(III) nitrate, 3Mg(N03)2-2Ce(N03)3-24H20, separation of praseodymium from lanthanum by, 2 57 Magnesium chloride, anhydrous, 1 29 5 154n. 6 9 Magnesium cyclopentadienide, 6 11 Magnesium rare earth nitrates,... 

This method has been considered the best of the classical separation procedures for producing individual elements in high purity. The most suitable compounds are ammonium nitrates (for La, Pr, and Nd) and double magnesium nitrates (for Sm, Eu, Gd). Manganese nitrates have also been used for separation of lanthanides of the cerium group (La-Nd). Bromates and sulphates have been used in the separation of the yttrium group (being the heavy lanthanides or HREE)... 

The cerium may now be removed from this solution by the bromate method (synthesis 14). Then the resulting solution is treated as before with excess oxalic acid or sodium suKate, the precipitates are again converted to hydrous oxides, and the latter are again dissolved in nitric acid. The rare earths from monazite are generally converted to double magnesium nitrates, 3Mg(N03)2-2(R.E.)-(N03)3 24H20 (synthesis 15), for preliminary fractionation. The rare earths from xenotime, after complete removal of cerium, may be converted to bromates (synthesis 17), and fractional crystallization of these salts may be commenced. 

To the double sulfate precipitate, 2 1. of water and 2 1. of 15 iV ammonia solution are added and the mixture is well stirred until the textxire of the precipitate indicates conversion to hydrous oxides (see synthesis 12D). The hydrous oxide precipitate is washed (by decantation) with large volumes of water in a 5-gal. crock until the washings, removed by siphoning, are only very slightly basic. The precipitate is then dissolved in the least amount of concentrated nitric acid. Cerium is next removed from this solution by the bromate method (see synthesis 14), and the remaining rare earths are converted to double magnesium nitrates (synthesis 15). 

If the material is to be separated into the cerium and yttrium groups of rare earths by precipitation of the double sulfates of the former, removal of the last trace of cerium is unnecessary since it does not seriously interfere in the fractionation of the cerium group double magnesium nitrates. It is important, however, that there be no ceriuni in a bromate series,... 

To 3500 g. of a cerium-free rare earth oxide mixture in a 16-in. porcelain dish is added sufficient water to wet all portions of the mass. The thick paste so obtained is treated with 4.2 1. of concentrated nitric acid in small portionsf and heated until solution is complete. The magnesium nitrate may now be added in the form of Mg(N03)2-6H20 crystals (810 g.) dissolved in 1.51. of water. If, however, many large series are to be set up, it is more... 

Yttrium-group earths, containing samarium, separation from mona-zite by magnesium nitrate, 2 56 separation by fractional crystallization of bromates, 2 56, 62 separation from cerium earths by double-sulfate method, 2 44, 46... 

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