Vol 13 Iss. 1

From year to year the sphere of application of X-Rays to the solution of both theoretical and practical problems becomes wider and wider. Thus the X-Rays are now applied for the purpose of identification of crystalline substances. The unequaled excellence of the X-Ray method is particularly manifest in geology and mineralogy. For a long series of minerals of vase industrial importance, as iron, nickel, manganese, and copper ores, clay and cement minerals, fine fractions of rocks, ochrous Mo-, Sb-, As-, W-minerals, etc. all other methods of investigation (chemical, optical, mechanical, etc.)' because of the pulverulent character of the objects, can give no positive results or meet with great difficulties in their application. In these cases the X-Ray method is the only efficacious method of investigation. It proves also to be the only method to apply in determining such and such peculiarities or changes in the crystalline structure of the substances under consideration. In the study of isomorphic groups of minerals this method renders unique services in clearing up the characteristic peculiarities of isomorphic replacement and changes in crystalline structures which are connected therewith. In every investigation of crystalline substances the X-Ray method must be applied side by side with all other methods of investigation, because it gives the possibility of ascertaining the most important, perhaps, of all the constants of a crystalline substance, namely the dimensions of the elementary cell and the scheme of the position, of atoms or ions in the structure. The X-Ray method of investigation acquires greater and greater authority with chemists, mineralogists and miners. Yet a wide application of this method for the purpose of identification of crystalline substances has been till now greatly hindered by the absence of more or less comprehensive X-Ray determinative tables adopted to the purpose of X-Ray mineralogical diagnostics. Disconnected works on separate minerals, or groups of them, scattered in literature though containing some X-Ray data, did but little to eliminate this defect, because, first, they were not adopted to the purpose of identification, and, secondly, they concerned a comparatively small number of minerals. In later works of 1935 and 1936 some authors try to adopt X-Ray data to the purpose of identification, but in these works the problem of producing any X-Ray determinative tables is solved only under a particular form, for a separate group of minerals studies by the authors. The present work constitutes the second issue of the X-ray determinator.