부산대학교 도서관

An accurate photometric method for determining a small amount of bismuth in steel, iron and ferrotungsten has been studied. After separating a bulk of Fe(III) with butyl acetate, citric acid and ethylenediamine tetraacetic acid are added, and the solution is heated so as to mask completely the other metals remained. Sodium cyanide is added, and pH of the mixture is adjusted to 8.5±0.2, within which no disturbance is expected from Fe(III) and Cu(II). The bismuth is extracted as diethyldithiocarbamate into carbontetrachloride, and the absorbancy is measured at 372mμ. Ferrotungsten is decomposed with nitric, hydrofluoric and perchloric acids and the deposited tungstic acid anhydride is filtered. The precipitate is dissolved with sodium hydroxide for recovering the bismuth adsorbed in it, added with a quantity of ammonium nitrate, and neutralized with hydrochloric acid. Then, bismuth is coprecipitated with iron carrier as hydroxide by the use of ammoniac water. In this method, even antimony and a small amount of tellurium do not interfere, because Sb(III) has been oxidized to Sb(V) by perchloric acid, and Te(IV) has been almostly separated with Fe(III) at the stage of preliminary extraction.