The stability of a colloidal dispersion has long been expressed in terms of the stability ratio. Based on the available theories of coagulation of colloidal dispersions, a novel expression, complying with the classical definition, is developed for the stability ratio. It accounts for the contributions of both primary and secondary minimum coagulations to the overall rate of coagulations. In addition, it can also be regarded as the result of a combination of the kinetic theory of an ideal gas and the Smoluchowski theory with Fuchs' correction, considering the interaction between identical spherical particles and their surfaces immersed in a symmetrical electrolyte solution. The agreement with experimental data suggested that it is superior to the classical ones in describing the weak dependence of the stability ratio on the particle size and the valence of the counterion, by emphasizing the importance of the secondary minimum coagulation in dispersion stability and the complementation between the two modes of coagulation.

The Xiangxi UNESCO Global Geopark (XUGG) contained the largest karst red stone forest landscape and the Global Standard Stratotype-section and Points (GSSPs) in the Cambrian System. Those geoheritage contribute to a better understanding of Earth’s evolution. Therefore, it is of great significance to conduct geoscience research and geosciences popularization in the XUGG. In this study, we took the XUGG as the research object, and analyzed the situation of the strengths, weaknesses, opportunities and threats in the development process of geopark popular science tourism by using SWOT analysis method, in order to realize the sustainable development of geoparks in popular science tourism. The results show that: the XUGG continent possesses geoheritage, good facilities and unique advantages of popular science development. In the new era, we should optimize the development of popular science tourism in Geoparks, realize the two-way interactive participation of popular science, explore the community participation model of popular science tourism, and promote the development of rustic areas with unique geological resources. Then, it not only facilitates the broadcasting and popularization of earth sciences, but also contributes to the sustainable development of geotourism.

The colloidal stability, one of the basic and important properties of a colloidal dispersion, is commonly evaluated in terms of the stability ratio. In this study, a recently developed expression for the stability ratio is updated, by reformulating the fraction of successful collisions leading to secondary minimum coagulation. The updated formula reinterprets the statistical meaning of the fraction of successful collisions leading to primary or secondary minimum coagulation, ensuring that the total fraction of successful collisions is always less than or equals to 1. It was shown to be superior to the available expressions in accounting for the contribution of the primary and secondary minimum coagulations on the stability ratio. It can well interpret the stability of colloidal dispersions of spherical particles; moreover, it is of great potential to be applied to colloidal dispersions of plate-like particles. In addition, this formula is found to be consistent with the concept of the critical coagulation concentration and well interpret the effects of particle size, counterion valence, surface potential, and Hamaker constant on the colloidal stability.