~Effect of Foreign Salts.~--Sodic hyposulphite almost completely removes the colour. Copper salts liberate iodine; but when this has been removed by boiling and the cuprous iodide has been filtered off there is no further interference. Dilute solutions of lead salts give no colour. PRACTICAL EXERCISES. 1. A fusible alloy is made up of 8 parts of bismuth, 5 of lead, and 3 of tin. What weight of oxide of bismuth, Bi_{2}O_{3}, would you get on the analysis of 1 gram of it? 2. What weight of bismuth can be got from 2 grams of the subnitrate BiONO_{3}.H_{2}O? 3. How would you detect and separate arsenic, lead, and copper in a sample of bismuth? ANTIMONY. Antimony occurs in the native state, but is rare; its common ore is antimonite, the sulphide (Sb_{2}S_{3}). Jamesonite and other sulphides of lead and antimony are frequently met with. Sulphide of antimony is also a constituent of fahlerz and of many silver ores. Antimonite occurs generally in fibrous masses, has a lead-like metallic lustre, is easily cut with a knife, and melts in the flame of a candle. Antimony itself has a very crystalline fracture, is brittle, and has a bluish-white colour. It is used in the preparation of alloys with lead and tin for the manufacture of type-metal. It is readily fusible, and imparts hardness and the property of taking a sharp cast to its alloys. It is practically insoluble in hydrochloric acid. On boiling with strong nitric acid it is converted into antimonic oxide (Sb_{2}O_{5}), which is a powder almost insoluble in this acid or in water, but which may be got into solution with difficulty by the prolonged action of hydrochloric and tartaric acids. Antimonic oxide is converted on ignition into the tetroxide (Sb_{2}O_{4}) with loss of oxygen. Antimony forms two series of salts, antimonious and antimonic; and advantage is taken of this in its determination volumetrically. Either sulphide of antimony yields antimonious chloride on boiling with hydrochloric acid, sulphuretted hydrogen being given off; and, in the case of antimonic sulphide, sulphur is deposited. Antimonious is converted into antimonic chloride by treatment with permanganate of potash in an acid solution. Antimonic chloride and potassium iodide react, forming antimonious chloride and free iodine. This latter may be got rid of by boiling. Sulphide of antimony is separated from the ore by liquation; this regulus is met with in commerce as "crude antimony." DRY ASSAY.