[977] Ztschr. f. Anal. Chemie, xxiv., 1885, p. 551.
§ 901. Detection and Estimation of Uranium.—Uranium forms uranous and uranic salts. Both classes of salts are not precipitated by SH2, but are precipitable by ammonium sulphide, and, therefore, in toxicological analyses are likely to be met with in conjunction with iron.
The sulphides of iron and uranium may be dissolved in strong hydrochloric acid, boiled to expel SH2, and the solution then oxidised with a little nitric acid; the solution is now alkalised with ammonium carbonate, which precipitates the iron as oxide and leaves the uranium in solution. On now acidifying with nitric acid in slight excess, a solution of sodic phosphate will precipitate uranium phosphate as a white precipitate, alkalies will give a yellow precipitate, alkaline carbonates a yellow precipitate soluble in excess. Barium carbonate also gives a precipitate, and is useful in separations. Uranium oxide gives a green glass in the oxidising flame with borax or with sodic metaphosphate.
V.—ALKALINE EARTHS.
Barium.
§ 902. The soluble salts of barium are undoubtedly poisonous, and are of frequent occurrence in the arts. The chloride of barium is used in the staining of wool, the nitrate and the chlorate in the green fires of the pyrotechnist, the oxide and the carbonate in the manufacture of glass. The chromate is used by artists under the name of “yellow ultramarine,” while the sulphate, technically known as “permanent white,” is, on account of its weight and cheapness, occasionally used as an adulterant of white powders and other substances. Barium sulphide, under various names, such as Bottcher’s depilatory, Thompson’s hair destroyer, Poudre épilatoire, and other names, is in commerce, and has caused poisonous symptoms.[978]