A Series of Abnormal Liesegang Stratifications.
A Series of Abnormal Liesegang Stratifications.
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一系列异常的 Liesegang 分层。
DOI：
10.1042/bj0140418
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发表时间：
1920
影响因子：
4.1
通讯作者：
E. Hatschek
中科院分区：
文献类型：
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作者：
E. Hatschek
本论文中描述的实验代表了一项研究的初步工作，在这项研究中，有必要在体积高达300cc的明胶样品中产生列色钢分层，并完全淹没在单一组分的水溶液中。因此，人们希望使用一种比硝酸银更便宜的材料，而且除了成本之外，还希望在明胶中产生一种与有机结构的某些矿物成分更接近的沉淀物。因此，我决定研究磷酸钙在明胶凝胶中的沉积。StephaneLeduc[1911]采用了碱性磷酸盐与硝酸钙的反应。他采用了列塞刚的方法，将一种反应成分的溶液滴在含有另一种反应成分的明胶凝胶膜上，得到了如此细的分层，它们起到了衍射光栅的作用。Liesegang的结论表明，这种效应是由凝胶表面起皱引起的[1913]。这种特殊的效果对我的目的是无益的，因为我的目的是要在相当深的凝胶中产生分层，因此我在试管中研究这种反应。这一步骤现在已为人所熟知：在试管中，将其中一种成分的适当浓度的溶胶部分填充，使其完全凝固，然后将另一种成分的水溶液（在任何情况下，其摩尔浓度都必须远远超过凝胶中的摩尔浓度）倒进去。经过一些初步的实验，没有必要详细描述，发现在100cc磷酸三钠溶液中含有10g明胶的凝胶，后者的浓度为结晶盐（Na3PO4）的3,2 -5或2%，可以获得最好的结果。12H20，即分别为7- 87,6 -57和5-26毫摩尔的Na3PO4)，在其上放置氯化钙、硝酸钙或氯化钙和氯化钠的混合物溶液。使用这种混合物，其中一种成分不参与反应，是一种众所周知的方法，可以降低反应成分的浓度，同时保持总摩尔浓度——它决定了扩散到凝胶中的速度——足够高。
THE experiments described in the present paper represent preliminary work for an investigation in which it was necessary to produce Liesegang stratifications in gelatin specimens having volumes up to 300 cc. and completely submerged in the aqueous solution of the one component. It was therefore desirable to employ a material less expensive than silver nitrate and, for reasons apart from the cost, to produce in thegelatin a precipitate more closely corresponding to some of the mineral constituents of organic structures. I accordingly determined to study the deposition of calcium phosphate in gelatin gel., The reaction between alkaline phosphates and calcium nitrate has been, used by StephaneLeduc [1911]. He used Liesegang's procedure, which con-sists in placing a drop of the solution of one reaction component on a film of gelatin gel containing the other, and obtained stratifications of such fineness that they acted as a diffraction grating. It has been shown conclusively by Liesegang that this effect is dueto wrinkling of the surface of the gel [1913]. This particular effect would have been useless for my purpose, which was to produce stratifications extending through a considerable depth of gel, and I accordingly studied the reaction in test tubes. This procedure isnow well known: a test tube is partly filled with the sol containing one of the components in suitable concentration, the sol is allowed to set completely, and the aqueous solution of the other component-which must, in all cases, have a molar concentration greatly in excess of that in the gel-poured on. After some preliminary experiments, which it is not necessary to describe in detail, it was found that the best results were obtained with gels containing 10 g. of gelatin in 100 cc. of trisodium phosphate solution, the concentration of the latter being 3, 2-5 or 2% of the crystallised salt (Na3PO4. 12H20, ie respectively 7-87, 6-57 and 5-26 millimoles of Na3PO4), on which were placed solutions of calcium chloride, calcium nitrate or mixtures of calcium chloride and sodium chloride. The use of such mixtures, one constituent of which takes no part in the reaction, is a well known device for reducing the con-centration of the reacting constituent, while keeping the total molar concen-tration-which settles the rate of diffusion into the gel-sufficiently high.