溶胶的净化.ppt

四、实验步骤 * * Experiment 15 Preparation and Properties of Colloidal Systems Purposes 1. Understand the preparation method of colloid. 2. Verify the properties of colloidal system. 3. Observe the protective action of macromolecular solution to colloid. Principles Preparation of the colloid (1) Chemical reaction method Preparation Fe（OH）3 sol by hydrolyzation of FeCl3: Fe(OH)3+ HCl = FeOCl + 2H2O FeOCl = FeO+ + Cl- A colloidal suspension of antimony (Ⅲ) sulfide is produced by the reaction of hydrogen sulfide with antimony potassium tartrate dissolved in water. 2(SbO)K(C4H4O6) + 3H2S = Sb2S3 + 2KHC4H4O6 + 2H2O H2S (excess) = H+ + HS- (2) The physical condensation method Sulfur sol is prepared with the change solvent method: The solubility has different properties because the substance is in the different solvents. Add sulfur saturated solution of ethanol to water. Because the sulfur is insoluble in water, sulfur atoms gather each other to form a sulfur sol. （2）分散法： 电弧法制备银溶胶： 银溶胶的制备包括分散和凝聚两个过程，即在放电时金属银原子因高温而蒸发，随即又被溶液冷却而凝聚成银溶胶。 2. Optical and electrical properties of the colloid Optical properties: When a strong beam of light is passed through a colloid, the beam becomes visible because the colloidal particles reflect and scatter the light. This phenomenon is called the Tyndall effect. Tyndall现象 （2）electrical properties 在外电场的作用下，胶粒在介质中定向移动的现象. 电泳示意图 3、溶胶的净化: 利用胶粒、大分子不能 透过半透膜其他杂质离 子能够透过半透膜的特 点除去过多的电解质。 4、溶胶的聚沉 当溶胶的稳定因素遭到破坏，胶粒碰撞时合并变大，胶粒就从介质中析出而下沉，称为聚沉。 若在溶胶中加入电解质后，把扩散层中的反离子斥入吸附层，胶粒的荷电数减少甚至消失，水合膜和扩散层随之变薄或消失，胶粒便发生聚沉。带两种相反电荷的溶胶混合也可以产生聚沉。 5. 动物胶对溶胶保护作用 在溶胶中加入一定量的动物胶，能显著提高溶胶的稳定性，这种现象称为高分子对溶胶的保护作用。 产生保护作用的原因是高分子物质吸附在溶胶粒子表面，包围住胶粒，形成一层高分子保护膜，使其对介质的亲和力加强，阻止了胶粒之间的直接接触，增强了溶胶的稳定性。 （1）水解法制备Fe(OH)3溶胶： 在50mL烧杯中加入30mL蒸馏水，加热至沸，慢慢滴入3ml 0.1mol·L -1FeCl3溶液，并不断搅拌。加毕继续保持沸腾5min，即可得到红棕色的Fe(OH)3溶胶，其结构式可表示为： {m［Fe(OH)3］nFeO+(n－x)Cl-}