The oxidases and other oxygen - catalysts concerned in biological oxidations / by J. H. Kastle.

  • Joseph Hoeing Kastle
Date:
[1910]
Catalogue details

Licence: In copyright

Credit: The oxidases and other oxygen - catalysts concerned in biological oxidations / by J. H. Kastle. Source: Wellcome Collection.

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    platinum foil. On the other hand, such solutions, in the absence of platinum, suffered no reductions in the current ofi97h^lr°gen a ^g Then followed the beautiful discovery of Graham ( ) m 1866 68, that platinum and particularly palladium, and other metals to> a slight extent, have the power of absorbing considerable amounts of hydrogen under the influence of moderate amounts of heat or as the result of electrolysis. Furthermore, the hydrogen m these metallic combinations was recognized as active m the sense that it could reduce iodine to hydriodic acid, ferric salts to ferrous salts, etc changes which can not be effected by ordinary molecular hydrogen in the cold. According to Graham, the hydrogen under these con- ditions becomes polarized, its affinity for oxygen thereby being greatly increased. Such hydrogen, for example, was found to combine with oxygen even in the cold, with the production of water. Now in the course of his own investigations Hoppe-Seyler found that freshly prepared palladium hydride has the power of reducing copper sulfate to metallic copper, that it decolorizes a solution of indigo, and reduces potassium permanganate in neutral solution to manganese dioxide, or in acid solution to a manganous salt; that it converts quinone into quinhydrone and changes oxyhemoglobin to methemo- globin. He found further that these powerful reductions are brought about only when the palladium hydrogen compound is fresh; if allowed to stand it loses these properties, while it is still found to contain hydrogen. These reducing actions correspond entirely to those exhibited on dissolving zinc or tin in dilute acids; in other words, they are effected by nascent or active hydrogen. According to Hoppe-Seyler the most interesting reduction which can be effected by active hydrogen is that of molecular oxygen to water, whereby —OH or — O—O —H, and finally water and active oxygen, are formed successively. He found further that if one shakes some palladium foil saturated with hydrogen with a dilute starch paste containing potassium iodide and air, there is produced in a few moments a dark-blue solution of the iodide of starch. In other words, through the influence of the hydride of palladium, potassium iodide is oxidized by the oxygen of the air, a change which ordinarily takes place only with extreme slowness. If now the foil be boiled with water and heated to redness to expel the hydrogen, it no longer has the power to form the iodide of starch when shaken with a solution of potassium iodide and starch in contact with air. Similarly, indigo is oxidized to isatin and ammonia to ammonium nitrite, benzene to phenol and toluene to benzoic acid, when these several substances in aqueous solution are shaken with air and palladium hydride. All of these changes go to show that we have here to deal with very vigorous oxidations, and it can not be doubted