Chemical properties of Praseodymium

The salts of praseodymium are derived from the basic oxide Pr₂O₃. They are leek-green in colour, and their reflection spectra or the absorption spectra of their solutions exhibit characteristic absorption bands. The conductivities of praseodymium salts in aqueous solution are in harmony with the view that the salts are derived from a fairly strong triacid base. The following results, for example, refer to the chloride at 25° (v = dilution in litres per gram equivalent): -

PrCl3	v=	31.3	62.6	125.2	250.4	500.8	1001.6
	λ=	05.3	112.25	120.1	125.1	130.4	135.7

Praseodymium is of interest in that it forms a dioxide, PrO₂. According to Brauner, the dioxide is a weak base, and gives rise to a basic sulphate, 2Pr₂O₄.SO₃ + 2½|H₂O, and a basic acetate, (CH₃.CO)₃.Pr^IVO.Pr^IV(OH)₃ or in (CH₃.CO)₂.Pr₂^IIIO₂(OH)(CO.CH₃) + H₂O. The same authority also mentions an acetate of the constitution (CH₂.CO)₂Pr^IIIO.O.O.Pr^III(OH)(CH₃.CO) + H₂O.

Numerous compounds of praseodymium have been described by von Scheele.

The following results have been obtained: -

2[Pr] + 3(O) = Pr₂O₃ + 412.4 Cals.
[Pr₂O₃] + 6HClaq. = 2PrCl₃aq. + 3H₂O + 106.2 Cals.
[Pr₂O₃] + 6(HCl) = 2[PrCl₃] + 3[H₂O] + 147.8 Cals.
[Pr₂O₃] + 3[H₂SO₄] = [Pr₂(SO₄)₃] + 3[H₂O] + 125.7 Cals.
[PrCl₃] + Aq. = PrCl₃aq. + 33.5 Cals.
[PrCl₃.H₂O] + Aq. = PrCl₃aq + 28.9 Cals.
[PrCl₃.7H₂O] + Aq. = PrCl₃Aq. + 5.3 Cals.
[Pr₂(SO₄)₃] + Aq. = Pr₂(SO₄)₃aq + 36.0 Cals.