Liesegang Phenomenon Research Articles

Chemistry

ALTHOUGH the Liesegang phenomenon, having engaged the attention of mineralogists, histologists and colloid chemists, has given rise to an extensive and scattered literature, the present work is the first monograph devoted exclusively to the subject. The author gives a full account of the experimental material, beginning with Liesegang's original silver chromate rings and enumerating the numerous other combinations of reactants which have since been found to produce periodic precipitates in certain gels andwithin certain limits of concentration. He then devotes a chapter to the various theories so far proposed, which have in turn postulated metastable super saturation, adsorption at the precipitate, membrane formation, variations in the rate of diffusion, periodic coagulation of a colloidal reaction product and periodic inhibition of precipitation by the second (soluble) reaction product as the principal agency. Most of these theories are based on a few, or even on isolated, examples and are incapable of explaining others. This is not really surprising, as there is no a priori reason for assuming that the mechanism of periodic precipitation is necessarily the same whatever the reaction producing it.

The Liesegang Phenomenon applied to the Lake Superior Iron Formations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Liesegang Phenomenon applied to the Lake Superior Iron FormationsR. J. HartmanR. J. HartmanMore by R. J. Hartman and R. McC. DickeyR. McC. DickeyMore by R. McC. DickeyCite this: J. Phys. Chem. 1932, 36, 4, 1129–1135Publication Date (Print):April 1, 1932Publication History Published online1 May 2002Published inissue 1 April 1932https://doi.org/10.1021/j150334a004RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (481 KB) Get e-Alerts

The Problem of Physico-Chemical Periodicity

THE normal chemist is so well used to seeing This reagents pass away in a decently continuous fashion, that when he finds them attacking each other in a succession of recurrent spasms, he is a little apt to shy off. The thing is, perhaps, too nearly suggestive of heart-beats, of vital processes, and of human activities: domains into which chemists are warier of intruding than formerly, and which they prefer to leave to their bolder brethren, the physiologists and the historians. At all events, rhythmic, pulsating, or periodic reactions have seldom been systematically followed up in any general way by chemists. There have been, it is true, such detailed inquiries as Ostwald's on the periodic dissolution of a specimen of chromium in acid, as Bredig's on the pulsating decomposition of hydrogen peroxide by mercury, and as the numerous studies of the Liesegang effect in jellies; but Dr. Hedges and Dr. Myers have now worked their way to a more comprehensive survey than these, which they have summarised in a small monograph. The broad plan of this is, first to classify periodicities of various sorts, then to set forth the experimental factors that operate in each class, and to give in the end an indication of the views which the authors-themselves notable experimenters in the field-have formed as to underlying causes. The full and important bibliographic index contains about 300 references, of which about one-third centre in the Liesegang phenomenon. About twenty fall outside the last thirty years. The Problem of Physico-Chemical Periodicity. By Dr. E. S. Hedges Dr. J. E. Myers. Pp. 95 + 2 plates. (London: Edward Arnold and Co., 1926.) 7s. 6d. net.

Anomalous Liesegang stratifications produced by the action of light

The investigation to be described in the present paper was originally begun with the intention of studying the Liesegang phenomenon under conditions more strictly defined than have been observed hitherto, and more particularly with definite volume ratios of the reacting solutions. In all the experiments recorded in the literature the amount of solution placed on a given, or unknown, quantity of gel has been arbitrary and is generally not even stated. A quantitative treatment of the phenomenon is impossible a priori as long as this ratio is unknown, and would probably become simplest if one, or both, volumes were made—practically—infinite. In the course of the preliminary studies for such experiments an extremely striking anomaly, not observed so far, was discovered, which appears to deserve being put on record before the main investigation is completed. The reaction chosen for this work was the formation of lead chromate in agar gel by the interaction of lead acetate (dissolved in the gel) with potassium or sodium dichromate, or with potassium chromate. This reaction, in very low concentrations, produces extremely fine and numerous stratifications, which were first obtained by L. J. de Whalley; the low concentrations and the cheapness of the ingredients also made it eminently suitable for work involving the use of large volumes. Soon after its discovery the reaction was employed by the author and the results discussed in their bearing on some controversial points, in the paper quoted above. A normal specimen is illustrated in fig. 1 (Plate 8); in this, as in all other specimens photographed, the excess of soluble dichromate present in the gel has been removed by prolonged diffusion, so as to show the lead chromate strata as distinctly as possible.

The Liesegang Phenomenon and Concretionary Structure in Rocks

THE curious formations illustrated were produced during some experiments made to support a suggestion that the Liesegang phenomenon might be attributed to adsorption (Science Progress, x., 369, 1916). The tubes contained 15 c.c. of 1 per cent, agar gel, in which small quantities of either liver of sulphur or manganese sulphate had been dissolved, and were treated with 10 c.c. of a standard solution of the other reagent. Particularly in the case of the gels containing the polysulphides, the resulting stratification differed from that hitherto observed, in that many of the zones were separated into a number of concretions, which in some instances were joined by rods to those of the succeeding zone. The concretions were all sharply defined; the indistinctness of Fig. 2 is due to their being imbedded in the gel. The peculiar structure may be due to the presence in the gel of small nuclei in the shape of deposited sulphur, or possibly to the composite character of one of the solutes. The separate spheroids, once started, would grow by adsorption in the same way as the solid strata. To determine the exact conditions of their formation requires further investigation, but it should be possible to repeat the experiment with the carbonates of calcium and magnesium.