Chemical lecture experiments . Thelatter only is bleached. Litmus paper is similarly bleached. H2S02; indigo solution. 58. Reducing action. — Hydrosulphurous acid possessesstrong reducing properties and precipitates the metals mer-cury and silver from solutions of their soluble salts. Thereactions may be carried out in test-tubes by adding a smallquantity of hydrosulphurous acid to the respective saltsolutions. The reaction with cupric sulphate proceeds in two small quantity of the hydrosulphurous acid is added tothe dilute cupric sulphate solution, which is rapidly turnedfrom blue to
Chemical lecture experiments . Thelatter only is bleached. Litmus paper is similarly bleached. H2S02; indigo solution. 58. Reducing action. — Hydrosulphurous acid possessesstrong reducing properties and precipitates the metals mer-cury and silver from solutions of their soluble salts. Thereactions may be carried out in test-tubes by adding a smallquantity of hydrosulphurous acid to the respective saltsolutions. The reaction with cupric sulphate proceeds in two small quantity of the hydrosulphurous acid is added tothe dilute cupric sulphate solution, which is rapidly turnedfrom blue to green. As the reaction proceeds, the solutionchanges to a dark brown, and a precipitate is obtained con-sisting of metallic copper and cuprous hydride. The addition of sulphurous acid to cupric sulphate solu-tion produces no precipitate. Solutions of H2S02, H2S03, HgCl2, AgN03, CuS04. SULPHUR TRIOXIDE PREPARATION 59. By the union of oxygen and sulphur dioxide in thepresence of platinized asbestos. — (a) When a mixture of. Fig. 69 SULPHUR TRIOXIDE 159 sulphur dioxide and oxygen is passed over heated platin-ized asbestos, sulphur trioxide is formed. A 500 cc. 3-necked Wolff bottle is half filled with concen-trated sulphuric acid. A current of sulphur dioxide is con-ducted through a glass tube inserted in one of the necks ofthe Wolff bottle and dipping beneath the surface of thesulphuric acid. A glass tube, conducting oxygen, is thrustthrough another neck ofthe bottle and likewisedips beneath the surfaceof the acid. A short glasselbow is inserted in thecork in the third neckand is connected with abulb-tube or combustion-tube containing a 3 or 4 cm. length of platinized asbestos(Fig. 69). The gases are passed with approximately thesame degree of rapidity into the bottle and proceed un-changed through the platinized asbestos and bulb-tube intothe air. On heating the platinized asbestos, however, densewhite clouds of sulphur trioxide are formed. 2 S02 + 02 = 2 S03. 500 cc. 3-nec
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