Erbium bromate

Cerous iodates and the iodates of the other rare earths form crystalline salts sparingly soluble in water, but readily soluble in cone, nitric acid, and in this respect differ from the ceric, zirconium, and thorium iodates, which are almost insoluble in nitric acid when an excess of a soluble iodate is present. It may also be noted that cerium alone of all the rare earth elements is oxidized to a higher valence by potassium bromate in nitric acid soln. The iodates of the rare earths are precipitated by adding an alkali iodate to the rare earth salts, and the fact that the rare earth iodates are soluble in nitric acid, and the solubility increases as the electro-positive character of the element increases, while thorium iodate is insoluble in nitric acid, allows the method to be used for the separation of these elements. Trihydrated erbium iodate, Er(I03)3.3H20, and trihydrated yttrium iodate, Yt(I03)3.3H20,... 

Yttrium is one of the most abundant rare earth elements and its purification is easily accomplished. Yttrium fractions from a bromate series are freed from dysprosium, holmium, and erbium by fractional precipitation with ammonia, K2OO4, or NaNC>2. The latter is probably the most effective. Yttrium salts give no absorption lines ini the viable portion of the spectrum, consequently the removal of holmium and erbium is easily observed by the direct vision spectroscope. 

Erbium may be prepared from the erbium-yttrium fractions of a bromate series by methods similar to those used in purifying yttrium, except that erbium is concentrated in the less basic fractions. Fusion of the nitrates gives a rapid separation of these two elements. 

Thulium in a fairly pure state may be obtained by the long-continued fractionation of a bromate series. The separation of erbium and thulium is fairly satisfactory by this method alone. According to Welsbach 1 thulium is a mixture of three elements which he designated as thulium I, II, and III. Probably no better thulium material has ever been obtained than that prepared by James2 using the bromate method, which gave a homogeneous product after 15,000 operations. 

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