The alkali perchlorates and a new principle concerning the measurements of space-lattice cells
| Autor: | Alfred Edwin Howard Tutton |
|---|---|
| Rok vydání: | 1926 |
| Předmět: | |
| Zdroj: | Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 111:462-491 |
| ISSN: | 2053-9150 0950-1207 |
| DOI: | 10.1098/rspa.1926.0078 |
| Popis: | The perchlorates of potassium and ammonium, KCIO 4 and NH 4 CIO 4 , were investigated crystallographically first by Mitscherlich* in the year 1832, then more extensively by Groth in 1868, and later still more fully, in 1907, by T. V. Barker in Oxford, who also included the perchlorates of rubidium and caesium, RbCIO 4 and CsCIO 4 , in his investigations. The scope of all this work, however, only extended to the morphological characters, no optical properties or constants having been dealt with, except as regards some very roughly approximate data given by Groth for the potassium and ammonium salts, which, moreover, in the case of the potassium salt, has proved to be erroneous. The optical investigation of these salts is rendered exceptionally difficult by the fact that only very small crystals can be obtained; especially is this true of the three metallic salts, the largest obtainable crystals rarely reaching the size of a small pin’s head and the most perfectly developed ones being only half that size. The author has long considered it a matter of special importance that the optics of these alkali perchlorates should, if possible, be thoroughly worked out, and recent developments of the X-ray study of crystals, connecting structure with refraction, have rendered this all the more desirable. Such an investigation has, therefore, been attempted, and happily with complete success, although it has proved the most difficult one ever undertaken by the author. For reasons which will be clear from what follows, a complete remeasurement of the crystals of all four salts has also been made, with most satisfactory confirmation of the results of Barker, and extension of them to further important angles and a new “ setting.” The densities of the crystals as determined by Barker required no revision, as they were obtained, obviously with particular care, by the author’s mode of carrying out the Retgers immersion method, using a mixture of methylene iodide and toluene as the immersion liquid. Three outstanding results arose from the work of Barker. Firstly, it was shown that potassium, rubidium, and cæsium perchlorates form a eutropicallv isomorphous series of orthorhombic salts, resembling in this respect the sulphates and selenates of these same three metals studied by the author, and the alkali permanganates studied by Muthmann.* Secondly, ammonium perchlorate proved to be closely isostructural with rubidium perchlorate, just as the sulphates and selenates of the same two bases had been found to be by the author. Thirdly, Barker showed that these perchlorates and the corresponding permanganates are isomorphous with the barytes group of orthorhombic minerals, barytes BaSO 4 , celestine SrSO 4 , and anglesite PbSO 4 , and that the morphological constants (unit cell dimensions, as indicated relatively by the topic axial ratios) in the cases of barytes and potassium perchlorate and permanganate are so close that overgrowths and parallel growths of the two latter salts are readily formed from their solutions on the crystals of barytes. |
| Databáze: | OpenAIRE |
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