The light-scattering capacity (Tyndall effect) and colloidal behaviour of gelatin sols and gels
The light-scattering capacity (Tyndall effect) and colloidal behaviour of gelatin sols and gels
复制标题
DOI：
10.1021/j150275a014
复制
发表时间：
1927-05-01
影响因子：
--
通讯作者：
Dexter, ST
中科院分区：
文献类型：
--
作者：
Kraemer, EO;Dexter, ST
X是所用光的波长；m和n分别是色散相和介质的折射率。对于给定的系统，其中ni和n是恒定的，廷德尔效应的强度与粒子的平均体积成正比。因此，Tyndall效应直接揭示了系统色散的条件和变化。到目前为止，很少有人注意到这一性质与蛋白质的胶体行为有关的问题的重要性。的确，定性观察是对表面上的混浊现象进行的。其中对明胶体系最重要的是Dhéré和GorGolewski 1，他们注意到随着灰分含量的降低，明胶溶胶的混浊度或不透明度会大大增加。在稀释系统中使用提纯和脱灰的明胶，他们描述了温度高于3摄氏度时浑浊的消失，并观察到极少量的酸或碱足以在低于3摄氏度的温度下去除浑浊。研究发现，中性盐对这一目的的效果相对较差。他们首先清楚地描述了随着明胶凝胶浓度的增加，浑浊度增加到最大值，然后又下降。最大浑浊度出现在大约2.5%；10%的明胶凝胶与0.1%到1%的体系一样没有表面浑浊。在低温下，他们进一步观察到，明胶倾向于从稀释系统中沉淀出来。这些研究可能是第一次对高度脱灰的明胶(灰分低于0.1%)进行研究。后来，Arisz2用照片记录了甘油-水混合溶剂中的廷德尔效应明胶体系。尽管灰分含量和混合溶剂引起了并发症，但阿里西观察到的情况大致相同。
X, the wave length of the light used; and m and n are the indices of refraction of disperse phase and medium respectively. With a given system, for which ni and n are constant, the intensity of the tyndall effect is directly proportional to the mean volume of the particles. The condition andchanges of dis-persion of a system are therefore directly revealed in the tyndall effect. Very little attention has thus far been given to the significanceof this property in connection with the problems associated with the colloidal be-haviour of the proteins. Qualitative observations, it is true, have been made of superficial turbidities. The most important of these for gelatin systems are due toDhéré and Gorgolewski1 who noted the great increase in turbidity or opacity of gelatin sols as the ash content was decreased. Using purified and de-ashed gelatin in dilute systems, they described the disappearance of the turbidity above 3oC and observed the very small concentrations of acids or bases sufficient to remove the turbidity at temperatures below 3oC. Neutral salts were found to be relatively much less effective for this purpose. They first clearly described the increase in turbidity to a maximum and sub-sequent decrease as the concentration of the gelatin gels increased. The maximum turbidity was found to occur at approximately 2.5 percent; 10 percent gelatin gels were as free from superficial turbidity as o.; to 1 percent systems. At low temperatures, they further observed that the gelatin tended to precipitate out from dilute systems. These studies were probably the first to be made upon highly de-ashed gelatin (less than 0.1 percent ash). Somewhat later, Arisz2 recorded photographically the tyndall effects 0} gelatin systems in a mixed glycerine-water solvent. In spite of the complications due to ash content and mixed solvent, Arisz observed much the same