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此外，物質(zhì)在介質(zhì)中沉降時還伴隨有擴散現(xiàn)象。擴散是無條件的絕對的。擴散與物質(zhì)的質(zhì)量成反比，顆粒越小擴散越嚴重。而沉降是相對的，有條件的，要受到外力才能運動。沉降與物體重量成正比，顆粒越大沉降越快。對小于幾微米的微粒如病毒或蛋白質(zhì)等，它們在溶液中成膠體或半膠體狀態(tài)，僅僅利用重力是不可能觀察到沉降過程的。

In addition, the material in the medium is also accompanied by the deposition of the phenomenon of diffusion. Diffusion is unconditional. The diffusion is inversely proportional to the mass of the material, and the smaller the particle is, the more serious the diffusion is. While the settlement is relative and conditional, it is to be subjected to external forces. The settlement is proportional to the weight of the body, the bigger the particle is, the faster the settlement is. Particles of less than a few microns, such as viruses or proteins, they are in a solution to a colloidal or semi colloidal state, the use of gravity is not likely to observe the settlement process.