several organic acids, one of which is stearic acid. The fat glyceryl stearate is (C17H35COO)3C3H5. Reference: Any organic chemistry or any elementary chemistry. See also page 155 of the Appendix. MATERIALS. EXPERIMENT 60 Soaps, Cleansing Powders Cottonseed oil, alcohol, 40% solutions of sodium hydroxide, alcoholic solution of phenolphthalein, toilet soap, laundry soap, solution of castile soap, calcium chloride solutions, Sapolio or other scouring soap, Dutch Cleanser or other cleansing powder. APPARATUS. 500-cc. flask fitted with a one-hole rubber stopper and a straight glass tube 1 yard long, large evaporating dish, test tubes, beakers, funnel, filter paper. A. Preparation of Soap. (Instructor's Experiment.) 1. Pour 50 cc. of cottonseed oil into a 500-cc. flask. Add 100 cc. of alcohol and 15 cc. of a 40% solution of sodium hydroxide. Place the stopper with the long glass tube (reflux air condenser) in the flask, and heat for an hour or more. The alcohol condenses in the tube and runs back into the flask. Alcohol is not needed to make soap but it dissolves both the oil and the hydroxide and so causes the action between them to be more rapid. 2. Pour the mixture into a large evaporating dish or enamel pan and heat till the alcohol is driven off. Stir constantly. Cool the mixture. The solid substance is soap. Write the equation for the making of soap. Name all sub stances: (C17H35COO)3C3H5+3 NaOH → C3H5(OH)3+3 C17H35COONa 3. Shake some of this prepared soap with distilled water. Does it produce suds? B. Properties of Soap. (Student's Experiments.) 1. Free alkali in soap. Cut a piece of dry toilet soap and add to the freshly cut surface a few drops of an alcoholic solution of phenolphthalein without water. If a red color appears, free alkali is present. In the same way test a piece of laundry soap for free alkali. Why should woolen goods not be washed with a soap containing free alkali? 2. Free fat in soap. Shake a few shavings of dry soap in a test tube with 20 cc. of gasoline. Filter into a beaker. Allow the gasoline to evaporate. A greasy residue indicates unsaponified fat. 3. Water in soap. Place a few shavings of a fresh soap in a large test tube. Heat the tube gently and look for drops of water on cool sides of tubes. Result? Is it wise to buy a cheap, soft, highly scented or colored soap? Why? 4. Action of soap in hard water. If soap is added to a solution of a calcium or magnesium salt, an insoluble calcium or magnesium soap is formed. Hard water contains salts of calcium and magnesium and such waters form a curdy precipitate when soap is added. To 20 cc. of distilled water add 5 cc. of a pure castile soap solution. Shake and note the suds. Now add 5 cc. of a solution of calcium chloride. What is the white precipitate? Shake. Are suds formed? Write the equation and name all substances: 2 C17H35COONa+CaCl2 - 2 NaCl+(C17H35COO)2Ca C. Water Softeners. 1. When may water be made "soft" by boiling? Explain. Write equation. 2. Washing soda, Na2CO3, will precipitate calcium or magnesium salts in hard water as carbonates, thus removing the "hardness." Write equations to show. Test a soap powder for sodium carbonate by adding hydrochloric acid to 5 grams in a test tube and observe effervesResult? Test also a hard water soap. Result? cence. Note: There are many water softeners on the market; sodium carbonate, sodium phosphate, or sodium silicate are often the chief constituents. The action of these is to precipitate the calcium or magnesium salts as insoluble carbonates, phosphates, or silicates. D. Scouring Soaps and Cleansing Powders. 1. Boil 10 grams of a scouring soap, such as Sapolio, or a cleansing powder such as Dutch Cleanser, in a beaker with 50 cc. of water. Filter. 2. Add dilute hydrochloric acid to the résidue. If it effervesces, insoluble carbonates are indicated. Result? 3. The residue insoluble in dilute acid may be clay, fine sand, or pumice. Note your sample. 4. Add dilute hydrochloric acid to the filtrate. Effervescence indicates sodium carbonate. Result? APPENDIX THE METRIC SYSTEM THIS is the system used by scientists. It is used by everyone in most of the countries of Europe and, because of its convenience, is being used more and more in the United States and Great Britain. 1. Length: The unit is the meter. It is equal to 39.37 inches or 1.1 yards. The centimeter is the unit of length most used by the chemist. of a meter, or of an inch. It is 10 millimeters (mm.) = 1 centimeter (cm.) 10 centimeters 10 decimeters 1000 meters 2. Volume: =1 decimeter (dm.) 1 meter (m.) = 1 kilometer (km.) The unit used by the chemist is either the cubic centimeter or the liter. The volume of a flask may be given as 500 cc. or liter. One U. S. liquid quart=946.36 cubic centimeters, a little less than a liter. 1000 cubic millimeters = 1 cubic centimeter (cc.) 1000 cubic centimeters = 1 cubic decimeter 1000 cubic decimeters = 1 cubic meter 3. Weight: The unit is the gram. This is the weight of 1 cc. of pure water at its temperature of greatest density, 4° C. 10 milligrams (mg.) =1 centigram (cg.) The gram and the kilogram are the units of weight most generally used by the chemist. One ounce avoirdupois = 28.35 grams One pound avoirdupois = 453.59 grams = 2.2 pounds TEMPERATURES Centigrade and Fahrenheit and Absolute Scales The Centigrade Thermometer is the one used in scientific work. The abbreviation for centigrade is C. The boiling point of water on this thermometer is marked 100 and the freezing point is marked 0. The 100 equal divisions between these points are called degrees. The abbreviation for degrees is °. The boiling point of water is written 100° C. Degrees below zero are written as minus; thus, -20° C. means 20° below zero. The Fahrenheit Thermometer is the one commonly used in this country. On this thermometer the boiling point of water is 212° F. and the freezing point of water is 32° F. above zero. To change the Fahrenheit degrees to centigrade degrees, subtract 32 and multiply the remainder by, thus: C. = 5 (F.-32) To change centigrade degrees to Fahrenheit degrees multiply by and add 32 to the product, thus: F. = C. +32 The Absolute Temperature is the one used by scientists in the study of gas volumes. The point -273° C. is called the absolute zero. Absolute temperature is reckoned from this point. Degrees on the absolute scale are found by adding 273 to the readings on the centigrade thermometer. Thus : |