A text-book of inorganic chemistry / by G.S. Newth.

  • Newth, G. S. (George Samuel)
Date:
1900
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Licence: In copyright

Credit: A text-book of inorganic chemistry / by G.S. Newth. Source: Wellcome Collection.

    185/694 (page 165)
    dation, viz., CrjOs, in which condition it unites with sulphuric acid, forming chromium sulphate— KjCrjO^ + 4H2SO4 = K2SO4 + Cr2(S04)3 + 4H2O + 30. During the reaction, the red colour of the dichromate changes to the deep olive-green colour possessed by chromium sulphate. (7.) Many other highly oxidised salts yield oxygen when acted upon by sulphuric acid ; thus, with potassium permanganate, the following action takes place :— KsMnaOg + 3H2SO4 = K2SO4 + 2MnS04 + 3H2O 4- 60. (8.) If hydrogen peroxide be added to dilute sulphuric acid, and the mixture dropped upon a solution of potassium permanganate contained in a suitable generating flask, a rapid evolution of oxygen takes place at the ordinary temperature, thus— K2Mn20g + 3H2SO4 -I- 5H2O2 = K2SO4 -H 2MnS04 -b 8H2O -I- SOg. (9.) When strong sulphuric acid is dropped upon fragments of brick or pumice-stone, contained in an earthenware or platinum retort, and maintained at a bright red heat, the acid is decomposed into water, sulphur dioxide, and oxygen— H3SO4 = H2O -b SO2 -b O. The products of the decomposition are passed through water, which absorbs the sulphur dioxide, and also arrests any undecomposed sulphuric acid, and the oxygen is collected over water. When this process is used on a large scale, the sulphur dioxide is absorbed by being passed through a tower filled with coke, and down which a stream of water is allowed to trickle, and the solution so obtained can be utilised in the manufacture of sulphuric acid. (10.) Oxygen can be obtained from bleachmg-powder by methods which afford interesting instances of catalytic action.* The composition of bleaching-powder is expressed by the formula Ca(OCl)Cl. If this substance be mixed with water, and a small quantity of precipitated cobalt oxide added, and the mixture gently warmed, oxygen is rapidly evolved. The cobalt oxide, CoO, is the catalytic agent; it is able to combine with more oxygen to form • Experiments 315. 3®. 37. 152. “Chemical Lecture Experiments, new ed.