A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ...

  • Henry Enfield Roscoe
Date:
1881
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ... Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    193/792 (page 177)
    A thin stream of .sulphuric acid flows into a retort filled with broken bricks and heated to redness ; tlie acid splits up into sulphur dioxide, water, and oxygen, yielding 15'68 per cent, of its weight of the gas, or in practice 55 grams, of acid yield 6 litres of gas, thus :— H^SO, = SO2 + + 0. The resulting sulphur dioxide and water can be absorbed and condensed respectively by passing the gases through a tower filled with coke,, down which water trickles, whilst the oxygen can be collected in a gas-holder. The solution of sulphur dioxide may be returned to the vitriol chamber for the manufac- ture again of sulphuric acid. An apparatus for illustrating this decomposition on the small scale is described under Sulphuric Acid. (10) When baryta, BaO, is gently heated to dark redness in the air, it takes up an additional atom of oxygen, forming the dioxide, BaOo, but at a bright-red heat this parts with the additional atom of oxygen with the reproduction of baryta. By thus alternately varying the temperature, first leading air over the baryta contained in a porcelain tube, and then placing the tube in connection with a gas-holder and raising the tem- perature, and again repeating the process, a regular production of gas can be obtained from a small quantity of baryta.^ This simple method has not, unfortunately, come into general use, as the baryta loses its power of absorbing^' oxygen, chiefly owing to the fact that it combines with the silica of the tubes, and therefore requires frequent renewal. (11) Potassium manganate, KgMnO^, loses oxygen when heated in a cm-rent of steam, forming caustic potash and lower oxides of manganese, which when again heated absorb oxygen, the manganese being reproduced, so that the same portion may be used over and over again (Tessie du Motay). 87 Properties.—Oxygen is a colourless, invisible, tasteless, and inodorous gas, first, liquefied by Cailletet and Pictet in December, 1877.^ Oxygen gas is a little heavier than atmo- spheric air, having a specific gravity of ri0563 (air = 1) or 15'96 when hydrogen is taken as the unit. The combining weight, according to the researches of Stas, is not 16, as is ' Boussingault, Ann. CJiim. Phyn. [3] xxxv. ' See Vol. TT., part ii., pa<ie 517, A'o. 12