Silver periodate

Add 1 drop (0 05 ml.) of concentrated nitric acid to 2 0 ml. of a 0 5 per cent, aqueous solution of paraperiodic acid (HjIO,) contained in a small test-tube and shake well. Then introduce 1 op or a small crystal of the compound. Shake the mixture for 15 seconds and add 1-2 drops of 5 per cent, aqueous silver nitrate. The immediate production of a white precipitate (silver iodate) constitutes a positive test and indicates that the organic compound has been oxidised by the periodic acid. The test is based upon the fact that silver iodate is sparingly soluble in dilute nitric acid whereas silver periodate is very soluble if too much nitric acid is present, the silver iodate will not precipitate. 

In qualitative organic analysis, use is made of the fact that silver iodate is sparingly soluble in dilute nitric acid whereas silver periodate is very soluble. For water-insoluble compounds solutions in ethanol or in pure dioxan may be employed. 

Trivalent complexes of biguanide and periodate are also prepared commercially for water sanitation. The trivalent silver periodate, for example, is prepared by the action of potassium periodate and potassium hydroxide on Ag O ... 

Perhalates. Whereas silver perchlorate [7783-93-9] AgClO, and silver periodate [15606-77-6] AglO, are well known, silver perbromate [54494-97-2] AgBrO, has more recendy been described (18). Silver perchlorate is prepared from silver oxide and perchloric acid, or by treating silver sulfate with barium perchlorate. Silver perchlorate is one of the few silver salts that is appreciably soluble in organic solvents such as glycerol, toluene, and chlorobenzene. 

Silver foil is transformed by an aq. soln. of the trichloride into silver chloride and iodide silver oxide with an excess of the trichloride is transformed into the chloride and iodic acid with more silver oxide, silver iodate is formed and with an excess of the oxide and a boiling soln. some silver periodate is formed. Mercuric oxide is slowly transformed into mercuric chloride and oxide chlorine, oxygen, and possibly chlorine monoxide are evolved. Aq. soln. of the trichloride give a precipitate of iodine with a little stannous chloride with more stannous chloride, some stannous iodide is formed. Consequently, although chloroform extracts no iodine from the aq. soln., it will do so after the addition of stannous chloride. Sulphur dioxide and ferrous sulphate are oxidized. 

Salts of the first series are dipotassium tri-hy-drogen periodate, KgHglOg, silver periodate,... 

Periodic Acid—UIOj—192—is formed by the action of Cl upon an alkaline solution of sodium iodate. The sodium salt thus obtained is dissolved in nitric acid, treated with silver nitrate, and the resulting silver periodate decomposed with HjO. From the-solution the acid is obtained in colorless crystals, fusible at 180° (206° F.), very soluble in water, and readily decomposable by-heat. 

Silver nitrate, added to a periodate, forms a precipitate the color and nature of which depend e.g. on the amoxmt of extra HNO3. Confusing reports find products varying from slate-colored Ag3H2l06 to orange AgI04. Boiling the silver periodates in water causes them to become dark red. The freshly prepared compounds are readily soluble in NH3. 

---