教材“胶体”,有一个渗析实验,即把淀粉溶液与NaCl 溶液的混和液装入用玻璃纸(或肠衣)做的半透膜袋内,悬吊于盛有蒸馏水的烧杯中。几分钟后,取烧杯中的水少量分装于二支试管中,在一试管中滴入AgNO_3溶液,立即产生白色沉淀,可确认Cl~-的存在。在另一试管中滴入少量碘水,无现象产生,说明烧杯中不存在淀粉分子。从以上实验事实,说明了半透膜中存在小孔隙,使体积小的 Textbook “colloid”, there is a dialysis experiment, that is, the solution of starch and NaCl solution into the cellophane (or casing) made semipermeable membrane bag, suspended in a beaker containing distilled water. A few minutes later, a small amount of water in a beaker was dispensed in two test tubes. AgNO 3 solution was dropped into a test tube and a white precipitate immediately appeared confirming the presence of Cl ~. Drop in a small amount of iodine in another test tube, no phenomenon, indicating that there is no starch molecules in the beaker. From the above experimental facts, the existence of small pores in the semipermeable membrane, so that the small size