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Originally appearing in Volume V22, Page 911 of the 1911 Encyclopedia Britannica.

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MLL C M.L C M.L M L Obviously the fractions contain salts which increase in solu. bility as one passes from the See also:

LEFT

left to right, and with sufficient care and See also:

PATIENCE

patience this method permits a See also:

COMPLETE

complete separation. The salts which have been used include the sulphates, nitrates, chromates, formates, oxalates and malonates. R. J. See also:

Meyer (Zeit. anorg. Chem., 1904, 41, p. 97) separates the See also:

CERIUM (symbol Ce, atomic weight 140.25)

cerium earths by forming the See also:

double See also:

POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium See also:

CARBONATES

carbonates, e.g. K2Ce2(CO,)4. 12H20, which are soluble in potassium carbonate See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution, being precipitated in the See also:

order lanthanum, praseodymium, cerium and neodymium on diluting the solution; C. A. von Welsbach (Chem. See also:

NEWS

News, 1907, 95, p. 196; 1908, 98, pp.

223, 297) separates the metals of the See also:

YTTERBIUM (NEO-YTTERBIUM) [symbol, Yb; atomic weight, 172.0 (0=16)]

ytterbium See also:

GROUP

group by converting the basic nitrates into double ammonium oxalates and fractionating; C. See also:

James (ibid., 1907, 95, p. 181; 1908, 97, pp. 61, 205) formed the oxalates of the See also:

YTTRIUM [symbol, Y; atomic weight, 89.0 (0 =16)]

yttrium earths and dissolved them in dilute See also:

AMMONIA (NH3)

ammonia saturated with ammonium carbonate; by boiling this solution the earths are precipitated in the order yttrium, holmium and dysprosium, and See also:

ERBIUM (symbol, Er; atomic weight, 165-166)

erbium; he also fractionally crystallized the bromates (see, e.g. Jour. Amer. Chem. See also:

Soc., 1910, 32, p. 517, for thulium). Complex organic reagents are also employed. Neish (Jour. Amer.

Chem. Soc., 1904, 26, p. 78o) used See also:

META

meta-nitrobenzoic See also:

ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid ; O. Holmberg separates neodymium, praseodymium and lanthanum (and also See also:

THORIUM (symbol Th, atomic weight ,232.42 [0=16])

thorium) with meta-See also:

NITROBENZENE, C6H6NO2

nitrobenzene sulphonic acid, and has investigated many other organic salts (see Abs. J. C. S., 1907, ii. p. 90), whilst H. See also:

Erdmann and F. Wirth (See also:

Ann., 1908, 361, p. 18o) employ the 1.8 naphthol sulphonates. In order to determine whether any chosen method for separating these earths is really effective, it is necessary to analyse the fractions.

For this purpose two processes are available. We may convert the See also:

salt into the oxalate from which the See also:

OXIDE

oxide is obtained by See also:

HEATING

heating. A weighed quantity of the oxide is now taken and converted into sulphate by evaporating with dilute sulphuric acid. The sulphate is gently dried until the See also:

WEIGHT

weight is See also:

CONSTANT, BENJAMIN (1845-1902)

constant, and from this weight the See also:

EQUIVALENT

equivalent of the See also:

earth can be calculated. When repeated fractionation is attended by no See also:

CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change in the equivalent we may conclude that only one See also:

ELEMENT (Lat. elementum)

element is See also:

PRESENT

present. This See also:

PROCESS

process, however, is only rough, for the elements with which we are dealing have very See also:

close equivalents. A more exact method employs the Didymia f Praseodidymia Neodidymia spectra—spark, arc, See also:

PHOSPHORESCENCE

phosphorescence and absorption; the See also:

EVIDENCE (Lat. evidentia, evideri, to appear clearly)

evidence, however, cannot in all cases be accepted as conclusive, but when taken in See also:

CONJUNCTION (from Lat. conjungere, to join together)

conjunction with chemical tests it is the most valuable method. Chemical Relations.—The rare earth metals were at first regarded as divalent, but determinations of the specific heats of cerium by Mendeleeff and See also:

HILLEBRAND, KARL (1829–1884)

Hillebrand and of lanthanum and See also:

DIDYMIUM (from the Gr. &Segos, twin)

didymium by Hillebrand pointed to their trivalency; and this view now has See also:

general See also:

ACCEPTANCE (Lat. acceptare, frequentative form of accipere, to receive)

acceptance. They are comparatively reactive: they See also:

BURN, RICHARD (1709-1785)

burn in See also:

air to See also:

FORM (Lat. forma)

form oxides of the type Me203; combine directly with See also:

HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen at 2000–3000 to form hydrides of the See also:

formula MH2 or MH3; nitrides of the formula MN are formed by passing See also:

NITROGEN [symbol N., atomic weight 14.01, 0=16]

nitrogen over the oxides mixed with See also:

MAGNESIUM [symbol Mg, atomic weight 24.32 (0 = 16)]

magnesium; whilst carbides of the type MVIC2 are obtained in the electrolytic reduction of the oxides with See also:

CARBON (symbol C, atomic weight 12)

carbon. In addition to the oxides M203, several, e.g. cerium, See also:

TERBIUM [symbol Tb, atomic weight 159.2 (0=16)]

terbium and neodymium, form oxides of the formula MO2. The sesquioxides are bases which form salts and increase in basicity in the order Sc, Yb, Tm, Er, Ho, Tb, Gd, Sm, Y, Ce, Nd, Pr, La; the latter hissing with See also:

WATER

water like quicklime. The placing of these elements in the periodic table has attracted much See also:

ATTENTION (from Lat. ad-tendo, await, expect; the condition of being " stretched " or " tense ")

attention on See also:

account of the many difficulties which it presented.

The simplest See also:

plan of regarding them all as trivalent and placing them in the third group is met by the fact that there is not See also:

ROOM

room for them. Another See also:

SCHEME (Lat. schema, Gr. oxfjya, figure, form, from the root axe, seen in exeiv, to have, hold, to be of such shape, form, &c.)

scheme scatters them in the order of their atomic weights in the last four See also:

groups of the See also:

SYSTEM

system, but See also:

GRAVE

grave objections have been urged against this plan. A third See also:

DEVICE

device places them in one group as a See also:

BRIDGE

bridge between See also:

BARIUM (symbol Ba, atomic weight 137'37 [0=16])

barium and See also:

TANTALUM [symbol Ta, atomic weight 181•o (0=16)]

tantalum. This was suggested by Benedick in 1904 (Zeit. anorg. Chen., 1904, 39, p. 41), and adopted in See also:

Werner's table of 1905 (See also:

BEY (a modern Turk. word, the older form being beg, cf. Pers. baig)

Bey. 38, p. 914), whilst in 1902 Brauner (ibid. 32, p. 18) placed the group as a bridge on a See also:

PLANE

plane perpendicular to the planes containing the other elements, thus expanding the table into a three-dimensional figure. The question has also been considered by See also:

Sir See also:

William See also:

CROOKES, SIR WILLIAM (1832– )

Crookes (Jour. Chem.

Soc., 1888, 53, p. 487; 1889, 55, pp. 257 et seq.), whose inquiries led him to a new conception of the chemical elements.

End of Article: MLL

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