A handbook of chemical analysis : (adapted to the unitary notation) / based on the fourth edition of H. Will's Anleitung zur chemischen Analyse by F.T. Conington.

  • Will, Heinrich, 1812-1890.
Date:
1858
Catalogue details

Licence: Public Domain Mark

Credit: A handbook of chemical analysis : (adapted to the unitary notation) / based on the fourth edition of H. Will's Anleitung zur chemischen Analyse by F.T. Conington. Source: Wellcome Collection.

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    arsenious acid, sesquisalts of iron to protosalts, telluroiis and sclenous acids to metallic tellurium and selenium, &c. Metallic zinc is dissolved by sulphurous acid without any evolution of gas, sulphite and hyposulphite of zinc being formed (Zn^ + 3S02ir'^ = S03Zn2-|-S-0'^'Zu2 + 30ir-): if hydrochloric acid be present, hydrosulplmric acid is evolved, and may be detected by paper moistened with acetate of lead. By this reaction the smallest traces of sulphurous acid may be detected (in hydrochloric acid, kc). Most of the following sulphur-acids exhibit the same re- action. Aqueous sulphurous acid is decomposed by hydrosul- })huric acid, pentathionic acid being formed and sulphur deposited (öS 112 + ÖSO^IP^ vS-50«lI- + + 9ÜH2). When a solution of sulphurous acid is heated with chloride of tin and hydrochloric acid, yellow sulphide of tin is gradually precipitated: this reaction is rendered more delicate by the addition of a drop of a soluble copper-salt, owing to the forma- tion of black sulphide of copper. In this reaction a piece of paper moistened Avith acetate of lead should be held to the moutli of the tube, since the hydrosulphuric acid is frequently evolved in the free state. Sulphurous anhydride is readily and completely absorbed by peroxide of lead, sulphate of lead being formed (Pb^OH SO^^ S0n'b2). If a glass rod moistened with solution of starch and iodate of potassium be introduced into a gaseous mixture containing sulphurous anhydride, blue iodide of starch is at once formed. Most sulphites are decomposed by heat into a sulphate and a sulphide (4S03K2 = 3S04K'^ + SK2) : the earthy sulphites give off sulphurous anhydride, a metallic oxide being left. Estimation of Sulphurous Acid.— Sulphurous acid is the only oxygen compound of sulphur which (completely in very dilute solutions not containing more than 0-04 p. c. of acid) is converted by iodine into sulphuric acid (SO^H^ + IPO+ I2 = S0^IP+ 2III). This reaction serves not only for the detection, but, by the use of a standard iodine solution, for the volumetric estimation of sulphurous acid. Sulphurous acid may also be oxidised into sulphuric acid, and estimated as sulphate of barium. 0 3