Пустовалов Л.В., Новые данные о происхождении липецких и тульских железных руд

relating to the synthesis of limonite geodes. With that purpose to the wall of a quadrangular glass vessel a small piece of limestone was fastened by means of paraffine; the glass was then filled with quartz sand treated with aqua regia and washed with distilled water. After this the vessel was filled with a colloidal solution of ferric hydroxide. About the limestone piece commenced coagulation of ferric hydroxide; the latter settled about the limestone chip in concentric circles. On the 52-th day the experiment was looking as it shown by fig. 3 and On the 123-rd day, — as in figs. 5 and 6. On the 123-rd day the solution had completely coagulated, due to which the experiment was brought to its natural end. In principle, the author does not find any essential difference between his experiment and those of L i e s c g ang . L i e s e g a n g ’s periodic reactions took place in a medium of colloidal particles, while in the author’s experiment the reaction took place in a coarse-dispersion arenaceous medium. In L i e s e g a n g ’s experiment there took place a reaction, familiar to chemists, between chromic potassium and nitric silver. In the author’s experiment there goes on a coagula­ tion of a colloidal solution of ferric hydroxide; this process, according to L. D u c l a u x is also to be regarded as a chemical reaction, in which complex molecules of the type of (n. Fe20 3. Fe2) Cl6 are taking part. The author’s experiment showed that L i e s e g a n g ’s sporadic phenomena may arise not only in a colloidal medium, but in every given dispersion medium. In this fact the author sees the great importance of his experiment. A second experiment was set up by the author under similar conditions, but with the difference that before the experiment the previously applied col­ loidal solution Avas diluted to a double volume with distilled Avater. Under these conditions the coagulation of the the ferric hydroxide Avent on much more rapidly. On the 42-nd day the solution had already completely coagu­ lated (see fig. 7). A very important fact is that the concentre of broAvn ferric oxides was located in that case not at the very limestone chip, but at some distance from it, while betAveen the limestone chip and the brown ring the sand acquired a perfectly white colour. Consequently, in presence of diluted colloidal solutions of ferric hydroxides which are the most commonly observable under natural conditions, the concentres of coagulating ferruginous substance are dis­ posed at a certain distance from the source of coagulation. The results of the described experiments are compared by the author with the process of limonite formation in the ore-bearing seam of the environs of Lipetsk and Tula. The author believes the most correct explanation of L i e s e g a n g’s pheno­ mena to be that given in the Avork of M. Z s i g m o n d y (Kolloidchemie, V Aullage, I Teil, S. 220—221, Leipzig, 1925). According to that explanation the role of the jelly in L i e s i g a n g ’s experiments is reduced to that of a lattice in the pores of which are entangled the increasing particles of solid substance, set in movement by the diffusion current (Diffusionstrom). From that point of view the author believes nearly every sedimentary rock to be a medium favouring the apparition of Liesegang’s phenomena, for every rock is penetrated by pores and may, therefore, be regarded as a space lattice. Moreover, every rock contains some coagulating agent. The author is therefore believing that every time when colloidal solutions penetrate into some rock, L i e s e g a n g ’s phenomena must arise. In the region of Tula and Lipetsk a certain part of the colloidal iron com­ pounds was naturally moving doAvnwards. Due to this beneath the ore bed Ave may often observe either sand with ferruginous bands (fig. 2, p. 60), or limestone also showing ferruginous bands (figs. 8 and 9). Apart from this, the author Avas studying a Devonian dolomite underlying