As is known from the elementary course of crystallography, to determine the symbol [r0, r1, r2, r3] of the belt axis of a hexagonal-isotropic complex from the symbols of two non-parallel faces (p0, p1, p2, p3) and (q0, q1, q2, q3) belonging to this belt, you can use the following technique (see article).
Ammonium bromostannate (NH4)2 Sn Br6 was obtained by pvof. N. S. Kurnakov by mixing SnBr4 + 2(NH4) Br aqueous solution in the presence of hydrobromic acid. Cubic crystals of lemon yellow color. About 50 crystals were reviewed to elucidate the structure.
Artificial Ullmanite NiSbS. A compound corresponding in chemical composition to the mineral ulmanite was obtained by Prof. N. S. Kurnakov and Art. J. Posternak (at the St. Petersburg Polytechnic Institute) and transferred to the Mineralogical Institute of the Mining Institute for crystallographic research. CoSbS compound. This compound was obtained (as well as NiSbS) by stud. I. Posternak, was given to me by Prof. N. S. Kurnakov. The walls of the voids in the alloy were dotted with irregularly arranged, thin-plate-like crystals with a strong metallic luster of steel-gray color.
For correct installation, 100 crystals were reviewed. The results of the revision and calculation of the probability of correct installation are given in the tables (see article). Using the example of asparagine, the legality of the decrease in the number of developed forms as the crystalline ball grows is extremely sharply and clearly demonstrated. In addition, during further crystallization, the appearance of any new forms that were not observed during the previous crystallization was never observed. From all the experiments described above, it clearly follows that the possibility of obtaining a much larger number of forms during the crystallization of a sphere, compared with what we observe during the free growth of crystals of the same compound.
Crystallization of this compound was carried out at a temperature of about +20 ° C from solutions in methyl alcohol, in which it dissolves quite easily even in the cold. When heated, solubility increases 57 crystals were revised. The results of the revision are shown in the table (see article).
When crystallization is accelerated by cooling the initially heated solution, the crystals of these compounds begin to take on an increasingly needle-like appearance. The crystals of the iodide compound are so small (no more than 1/2 mm in length) that their goniometric study seems extremely difficult and I preferred not to do it, especially since this compound very easily decomposes in solution. Crystals of the chloride compound have already been described earlier. However, after the final clarification by E. S. Fedorov of the principles of correct installation, the symbols of the faces of these crystals should be changed according to the transition determinant (see article).
CuSO4 + 5H20 crystals have been studied by several authors. The most complete study of crystals of this compound was carried out relatively recently by Th. V. Barker in the laboratory of R. Groth. Copper sulfate crystals, as is known, belong to the cynacoidal class of the triclinic system. CuS04 + 5H20 crystallizes (at t° = - + 20°C) from an aqueous solution in very well-formed thick-table crystals. The article includes a diagram for the correct installation of crystals.
In his article “Image of the structure of a crystal with vectorial circles” Prof. E.S. Fedorov outlines a graphical method for finding the densities of meshes of crystal faces (more precisely: the squares of the densities of the corresponding meshes). Anyone who has dealt with determining the densities of meshes of faces using this method knows that in this case one should make some constructions, not particularly complex, but nevertheless quite time-consuming.This article aims to show how the task can be simplified by reducing drawing work to a minimum.
Cobalt-nitro-aquo-dimethylglucimine was first obtained by L.A. Chugaev, who transferred it to the Mineralogical Institute (Mining Institute) for crystallographic research. For the research results and crystal measurement tables, see the article.
Cobalt-diamine-dimethylglucimine chloride was obtained by L.A. Chugaev and presented by him to the Mineralogical Institute for crystallographic research (see article). Goniometric measurements (on a university, goniometer by E. S. Fedorov) and optical observations in polarized light revealed that the crystals belonged to the tetragonal system, the class of which could not be determined.
Especially for triclinic crystals, when finding the faces of the vertical belt from tables of mesh densities, it is necessary to make a displacement of the defining faces, and such a displacement should be made with greater accuracy, compared with that which we can achieve graphically. In this case, it will be necessary to calculate the spherical coordinate ρ, which defines the faces after the disp;acement. Solving the question of such a calculation does not present any difficulty, and is already partly contained in one of the formulas given in the article by Sokolov and myself “Determination of the densities of networks of crystalline faces without the help of constructions".
With the slow crystallization of cobalti - amine - chloro - dimethyl - glucosimine at + 18-20 ° C, special, mysterious facets appear on some crystals of this compound. These faces differ primarily in their size, since they are usually larger than others and formed so perfectly that when measuring, you can guarantee accuracy of up to a few seconds. However, by their position they do not seem to belong to the crystal complex, as their symbols are extraordinarily complex, almost irrational.
Let's imagine a crystal measured on a universal, theodolite goniometer. Let's assume that we have to measure a face that has various defects in formation and gives not one but several signals (due to the development of vicinaloids). Under such conditions, the measurement accuracy is significantly reduced and rather large errors can be made in the calculations of the angles φ (along the vertical limb of the goniometer) and p (along the horizontal limb). Even if the edge is formed well enough, it is still often possible to vouch for the accuracy of only a few minutes, and greater accuracy is achieved only in exceptional cases.
Кобальти-амин-хлоро-диметил-глиоксимин был впервые получен Л, А. Чугаевым, предложившим его одному из авторов для кристаллографического исследования. Кристаллизация производилась при температуре около + 20°С. из растворов в воде с 5% содержанием уксусной кислоты. В этом растворителе исследуемое соединение растворимо на холоде довольно трудно, причем растворимость его при нагревании повышается. Порошок вещества, взятый в избытке, нагревался в растворителе на водяной бане приблизительно до температуры кипения; затем горячий раствор отфильтровывался и охлаждался при комнатной температуре (около + 20° С). Результаты исследований см. в статье.
A hemisphere with a radius of 5 mm was cut out of a soldered piece of calcite. with a diametrical plane (110) (plaques, cleavages). This hemisphere, glued with wax to a glass hemisphere of the same diameter, was suspended by a thread in a supersaturated NaNO3 solution. Previously, to clean the surface of the calcite hemisphere, the ball glued together in the above manner was immersed in a weak hydrochloric acid solution for several seconds.
Experiments on the crystallization of a hemisphere with a diameter of 5 mm, prepared from a K2Cr2O7 crystal with a central plane (100), were generally carried out in exactly the same way as in the crystallization of hemispheres cut from sodium chloride, aluminum, and chrome alum.
Crystals of potassium dihydroxide were measured by Schabus (Wien. Ak. Veg. 1850) and he also stated a very perfect cleavage along {001} and less perfect along {100} and {010}. Potassium dichromate from aqueous solutions (t = + 20° C.) is released in well-formed crystals with growth planes {001} or {101}, which, as is known, belong to the pinacoidal class of triclinic system of cubic type.
In brief reports of the 1st issue of volume I of the Mining Institute Notes” (p. 83), I reported on some experiments in the growth of spheres (hemispheres) prepared from crystals of chrome and potassium alum. Similar experiments were carried out with rock salt (NaCl) crystals from Stassfurt. A welded piece of such salt was turned into a hemisphere with a diameter of 10 m.m. with a central plane (100) and glued with wax onto a glass hemisphere of the same diameter.
When studying certain physical properties of crystals, it is often advantageous to operate with crystals turned into spheres, since in this case we directly obtain the specific magnitude of change for each vector. However, as far as I know, no experiments have ever been made on the crystallization of spheres artificially prepared from a crystal of a given solid substance. Meanwhile, this form of crystal is important in the sense of reducing the influence of crystal planes on the crystallization currents that arise during the deposition of a substance from a solution.
