High-molecular compounds and laboratory work

Laboratory works are done only under the teacher’s instruction and supervision, with safety goggles, gloves and a lab coat, in a ventilated room; reagents are used in small amounts, nothing is tested by taste or smell, and concentrated acids and alkalis stay in the teacher’s hands. The textbook works are: (1) preparing ethylene by heating ethanol with concentrated H₂SO₄ and testing it with bromine water: C₂H₅OH → C₂H₄ + H₂O; (2) preparing acetylene by adding water to CaC₂ and observing its sooty flame: CaC₂ + 2H₂O → C₂H₂ + Ca(OH)₂; (3) dissolving glycerol in water and its deep-blue solution with freshly precipitated Cu(OH)₂; (4) preparing acetic acid from sodium acetate, its reaction with Mg and Zn (faster with Mg) and its decolourizing of NaOH + phenolphthalein: CH₃COOH + NaOH → CH₃COONa + H₂O; (5) the reaction of glucose with Cu(OH)₂ (blue solution in alkali, red precipitate on heating); (6) starch paste and its blue colour with iodine; (7) the biuret test of a protein (alkali + a little CuSO₄ — violet). Works that produce flammable gases (ethylene, acetylene) or heat concentrated sulfuric acid (1, 2, 4) are demonstrated by the teacher only. After each work the observation, equation and conclusion are written in the notebook; the workplace is cleaned and waste is collected as the teacher directs. Repeating these works at home is strictly forbidden.