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31 Laboratory work Experiment 1. Obtaining hydrosol rosin. Add 2 drops of 2% solution of rosin in alcoholin a flask with 10 ml of distilled water. When the mixture is stirred, a milky white opalescent sol is obtained. What is the dispersed phase and the dispersion medium? How is the sol obtained? Explain the formation of the sol. Experiment 2. Observation of light scattering. The tube with hydrosol rosin is placed in the path of the light beam. Observations are made at an angle of 90 ° to the direction of the light beam. In parallel, the same experiment is performed with water. Note the difference in light scattering by both solutions. Explain the reasons for the observed optical phenomenon. What is it called? Experiment 3. Preparation of iron (III) hydroxide sol. The iron (III) hydroxide sol is formed by deep hydrolysis of iron (III) chloride during boiling. The formation of the ionic stabilizer is based on the reactions: FeCl 3 + 3H 2 O → Fe (OH) 3 + 3HCl Fe (OH) 3 + HCl → FeOCl + 2H 2 O FeOCl → FeO + + Cl – Write the formula for micelles of iron hydroxide sol. Experiment 4. Preparation of sols of Berlin azure in various ways. Prepare colloidal solutions of ferric hexacyanoferrate (II) from solutions FeCl 3  and K 4 [Fe (CN) 6 ] в in 2 tubes with a normality of 0.005 in the following proportions: a) 3 ml of FeCl 3  solution and 1 ml of K 4 [Fe (CN) 6 ]solution b) 3 ml of K 4 [Fe (CN) 6 ]solution and 1 ml of FeCl 3  solution Check the sign of the particle charge of the sol with filter paper. The deter- mination of the charge sign is based on the fact that the surface of filter paper is charged negatively, and the water impregnating the paper is positive. Apply a drop of colloidal solution a) and next a drop of solution b) on the filter paper with a pipette. The sol with positively charged particles is adsorbed on the paper and forms a stain stained in the center and colorless on the edges. The sol with negatively charged particles is not adsorbed and forms a uniformly stained spot. Filtration paper with the results of the analysis is glued into the notebook. How is the sol obtained? Write the equation for the reaction for obtaining the sol. Write the formulas for the micelles for both sols. Experiment 5. Determination of the coagulation threshold of iron hydrox‑ ide sol. Make out experiments with two electrolytes: 2 M KCl and 0.0005 M K3 [Fe (CN)6]. Prepare solutions of electrolytes of various concentrations. Dispense volumes of electrolytes and water according to the table. Add 5 ml