此外，物質(zhì)在介質(zhì)中沉降時(shí)還伴隨有擴(kuò)散現(xiàn)象。擴(kuò)散是無(wú)條件的絕對(duì)的。擴(kuò)散與物質(zhì)的質(zhì)量成反比，顆粒越小擴(kuò)散越嚴(yán)重。而沉降是相對(duì)的，有條件的，要受到外力才能運(yùn)動(dòng)。沉降與物體重量成正比，顆粒越大沉降越快。對(duì)小于幾微米的微粒如病毒或蛋白質(zhì)等，它們?cè)谌芤褐谐赡z體或半膠體狀態(tài)，僅僅利用重力是不可能觀察到沉降過(guò)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.