Chemical properties of Lanthanum

The salts of lanthanum are derived from the colourless basic oxide La₂O₃, and, if derived from colourless acids, are themselves colourless. Their aqueous solutions are devoid of absorption spectra.

The following values for the equivalent conductivities X of a number of lanthanum salts at 25° are in harmony with the view that the salts are derived from a fairly strong triacid base (v = dilution in litres per gram-equivalent): -

LaCl3	v=	21.3	42.6	85.2	170.6	341.1	682.2	1364.5
	λ=	101.7	108.6	114.9	122.3	126.5	131.9	136.4
La(NO3)3	v=	32	64	128	256	512	1024
	λ=	98.6	105.4	112.8	118.1	124.1	126.5
La2(SO4)3	v=	33.86	67.72	135.44	270.88	541.76	1083.52
	λ=	43.58	50.30	58.49	68.89	80.93	96.26

Noyes and Johnston have measured the equivalent conductivities of dilute solutions of lanthanum nitrate and sulphate over a wide range of temperature, and Johnston has calculated from the results that the ionic conductivity of the lanthanum ion varies with the temperature as follows: -

Temp. ° C.	0°	18°	25°	50°	75°	100°	128°	156°
⅓ La•••	35	61	72	119	173	235	312	388

2[La] + 3(O) = [La₂O₃] + 444.7 Cals.
[La] + 4[Al] = [LaAl₄] + 97.8 Cals.
[La₂O₃] + 6HClaq. = 2LaCl₃aq. + 3H₂O + 114.6 Cals.
[La₂O₃] + 6(HCl) = 2[LaCl₃] + 3[H₂O] + 160.6 Cals.
[La] + 3(Cl) = [LaCl₃] + 263.0 Cals.
[LaCl₃] + Aq. = LaCl₃aq. + 31.3 Cals.
[La₂O₃] + 3[H₂SO₄] = [La₂(SO₄)₃] + 3[H₂O] + 138.2 Cals.
La₂(SO₄)₃ + Aq. = La₂(SO₄)₃aq + 34.6 Cals.