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在100mL的小烧杯里加入约40mL淀粉胶体和20mL食盐溶液的混和液体。 将两支半截试管,一端各用线扎紧半透膜,再倒入5～10mL蒸馏水,放到盛混和液的烧杯里。 0.5min后,向其中一支试管里滴加硝酸银溶液,出现白色沉淀,证明了氯离子可以透过半透膜的微孔;向另一支试管里滴加碘水,不发生变化,证明了淀粉胶体的微粒不能透过半透膜的微孔。另取一支盛有混和液的试管,沿内壁加入一滴硝酸银,可看出生成白色沉淀再加一滴碘水即变为蓝色。两组实验前后对比,现象十分明显。
A mixture liquid of about 40 mL of starch colloid and 20 mL of salt solution was added to a 100 mL beaker. The two half-tubes were spliced with a semi-permeable membrane at one end and poured into 5 to 10 mL of distilled water and placed in a beaker containing a mixture of liquids. After 0.5 min, a solution of silver nitrate was dropped into one of the tubes and a white precipitate appeared. This proved that the chloride ions could pass through the micropores of the semipermeable membrane; the iodine water was dropped into the other tube and no change occurred. The starch colloid particles cannot pass through the micropores of the semipermeable membrane. Another test tube containing a mixture of liquids is added with a drop of silver nitrate along the inner wall. It can be seen that a white precipitate is formed and a drop of iodine water turns blue. Comparing the two groups before and after the experiment, the phenomenon is very obvious.