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一前言把少量的油加入水中时,油在水里形成小珠而互不混合的现象,在調制剂工作中是常見的。这是由于油和水兩界面上分子所受的引力不均衡,产生了很大的界面張力。它总想使液体縮小表面。而在一定体积时,球形占有最小的表面积,故油滴形成了圓球形,並且这些油滴还有合併到一起的趋势,因为合併后可以获得更小的表面积。很显然,假若設法降低它的界面張力,就可以緩和表面积的縮小趋势。例如把少量的油酸鈉加入油和水的混液中时,由于油酸鈉使油与水間的界面張力显著降低,故能使油和水适当地混合。类似油酸鈉这样有降低界面張力作用的物質,称为界面活性剂(Surface active agent)。换句話講,界面活性剂是能使溶剂界面張力降低的物質。油酸鈉使水的界面張力降低的能力如表1所示,降低界面張力的能力特称为界面活度。
Introduction The phenomenon of forming small beads of oil in water while mixing small amounts of oil with water is common in the work of the formulation. This is due to the unbalanced gravitational forces exerted on the molecules at both the oil and water interfaces, resulting in a large interfacial tension. It always wants to make the liquid shrink the surface. And at a certain volume, the sphere occupies the smallest surface area, so the droplets form a spherical shape, and there is a tendency for the droplets to merge together, since the combined surface yields a smaller surface area. Obviously, if you try to reduce its interfacial tension, you can ease the surface area of the shrink trend. For example, when a small amount of sodium oleate is added to a mixture of oil and water, oil and water can be properly mixed because sodium oleate significantly reduces the interfacial tension between oil and water. Such as sodium oleate to reduce the role of interfacial tension substances, called surfactant (Surface active agent). In other words, surfactants are substances that lower the interfacial tension of the solvent. The ability of sodium oleate to reduce the interfacial tension of water is shown in Table 1, and the ability to reduce the interfacial tension is termed interfacial activity.