In its character yttrium is closely allied to, and in nature is always associated with, cerium, lanthanum, didymium and erbium (see Rare Earths).
Of yttria, Y203, and 42.75 of the oxides of erbium, cerium, didymium, lanthanum, iron, beryllium, calcium, magnesium and sodium.
In 1841 Mosander, having in 1839 discovered a new element lanthanum in the mineral cerite, isolated this element and also a hitherto unrecognized substance, didymia, from crude yttria, and two years later he announced the determination of two fresh constituents of the same earth, naming them erbia and terbia.
Lanthanum has retained its elementary character, but recent attempts at separating it from didymia have led to the view that didymium is a mixture of two elements, praseodymium and neodymium (see Didymium).
LANTHANUM [[[symbol]] La, atomic weight 139.0 (0=16)] one of the metals of the cerium group of rare earths.
For details of the complex process for the separation of the lanthanum salts from cerite, see R.
Lanthanum oxide, La203, is a white powder obtained by burning the metal in oxygen, or by ignition of the carbonate, nitrate or sulphate.
Lanthanum hydroxide, La(OH) 3, is a white amorphous powder formed by precipitating lanthanum salts by potassium hydroxide.
Lanthanum chloride, LaC1 3, is obtained in the anhydrous condition by heating lanthanum ammonium chloride or, according to C. Matignon (Comet.
By evaporation of a solution of lanthanum oxide in hydrochloric acid to the consistency of a syrup, and allowing the solution to stand, large colourless crystals of a hydrated chloride of the composition 2LaC1 3.15H 2 O are obtained.
Lanthanum sulphide, La 2 S 3, is a yellow powder, obtained when the oxide is heated in the vapour of carbon bisulphide.
Lanthanum sulphate, La2(S04)3.9H20, forms six-sided prisms, isomorphous with those of the corresponding cerium salt.
Lanthanum nitrate, La(N03)3 6H 2 0, is obtained by dissolving the oxide in nitric acid.
Lanthanum carbide, LaC 2, is prepared by heating the oxide with carbon in the electric furnace (H.
It is decomposed by water with the formation of acetylene, methane, ethylene, &c. Lanthanum carbonate, La 2 CO 3 8H 2 O, occurs as the rare mineral lanthanite, forming greyish-white, pink or yellowish rhombic prisms. The atomic weight of lanthanum has been determined by B.
Soc., 1901, 17, p. 63) by ignition of lanthanum sulphate at 500° C., the value obtained being 139 (O =16).
From the crude oxide so obtained (which contains lanthanum and didymium oxides) the cerium may be separated by conversion into its double sulphate on the addition of potassium sulphate, the sulphates of the cerium group being insoluble in a saturated solution of potassium sulphate.