此外，物质在介质中沉降时还伴随有扩散现象。扩散是无条件的绝对的。扩散与物质的质量成反比，颗粒越小扩散越严重。而沉降是相对的，有条件的，要受到外力才能运动。沉降与物体重量成正比，颗粒越大沉降越快。对小于几微米的微粒如病毒或蛋白质等，它们在溶液中成胶体或半胶体状态，仅仅利用重力是不可能观察到沉降过程的。

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.