noun
definition
A chemical element (symbol La) with an atomic number of 57: a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air.
definition
An atom of this element.
Examples of lanthanum in a Sentence
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 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.
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 nitrate, La(N03)3 6H 2 0, is obtained by dissolving the oxide in nitric acid.
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.
Lines of lanthanum and carbon which are believed to belong to a low level showed systematically smaller angular velocity than the average.
In its character yttrium is closely allied to, and in nature is always associated with, cerium, lanthanum, didymium and erbium (see Rare Earths).
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).