The _chloride_ separates from solution at ordinary temperatures as the dodecahydrate, Sc₂Cl₆,12H₂O, which loses 9 molecules of water when kept for six hours at 100°. The trihydrate Sc₂Cl₆,3H₂O, is converted into scandia at a red heat, with the loss of 6 molecules of hydrogen chloride. The _iodate_, Sc(IO₃)₃,18H₂O, is obtained as an almost insoluble white crystalline powder by addition of ammonium iodate to a salt in solution; hydrates with 15, 13, and 10 molecules of water are known, and at 250° the anhydrous compound is obtained. It resembles the iodates of the cerium and yttrium group in being soluble in strong nitric acid, but the separation of thoria and scandia by this method is tedious and unsatisfactory.[427] [427] Meyer, Winter and Speter, _Zeitsch. anorg. Chem._ 1911, ~71~, 65. The _platinocyanide_, Sc₂[Pt(CN)₄]₃,21H₂O, was obtained by Crookes[428] by double decomposition of the sulphate with barium platinocyanide, in crimson monoclinic prisms, with a green fluorescence. It dissolves in water to a colourless solution. Orlov[429] shows that it can occur also in a second form, stable at higher temperatures; this is yellow, with a blue fluorescence and crystallises with 18 molecules of water. The two modifications resemble respectively the platinocyanides of the yttrium and of the cerium elements; in this respect, therefore, scandium occupies an intermediate position between the two groups. [428] _Phil. Trans._ 1910, A, ~210~, 359. [429] _Abstr. Chem. Soc._ 1913, ~104~, i. 27. The _sulphate_, Sc₂(SO₄)₃, is obtained anhydrous by evaporating the excess of acid from a solution of the oxide in the concentrated acid, care being taken to avoid too high a temperature. The compound dissolves very easily in water, and slowly hydrates itself with evolution of heat; no crystals can be obtained from the solution until it has been concentrated to the consistency of a syrup, when on cooling it slowly deposits the hexahydrate. This effloresces in a dry atmosphere, forming the pentahydrate, which appears to be the most stable hydrate at ordinary temperatures. According to Nilson, the hexahydrate loses 4 molecules of water when maintained at 100°. At 250° it becomes anhydrous; above that temperature, basic salts are formed. The _potassium double sulphate_, 3K₂SO₄,Sc₂(SO₄)₃, was shown by Nilson to resemble the analogous cerium compounds in being insoluble in a saturated solution of potassium sulphate. The _nitrate_, Sc(NO₃)₃,4H₂O, separates from concentrated solutions over sulphuric acid as the tetrahydrate; it is very soluble in water and alcohol, and extremely deliquescent.