— : 608 MAN IS MASTERING HIS MATERIAL WORLD metallic or nonmetallic ions to form a slightly electrovalent covalent acid or base or both. One may summarize the actions in neutralization and hydrolysis as follows: Neutralization is a reaction in which protons are donated by hydronium ions to hydroxyl ions to form the weakly electrovalent covalent compound, water. Hydrolysis, on the other hand, is the process in which the hydronium ions or the hydroxyl ions formed by the dissociation of water donate their charges to other negative or positive ions to form weakly electrovalent covalent compounds. There Are Many Important, Interesting Applications of Hydrolysis. Baking powders are mixtures of sodium bicarbonate with some salt which will hydrolyze to produce an acid solution and with starch to keep the mixture dry so that the desired reaction will not take place before it is required. When acid is added to sodium bicarbonate, carbon dioxide is produced. Thus: (H3O+), CI- + Na+, (HCO3)-—?- Na+, CI" + H2O + CO2. hydrochloric sodium sodium water carbon acid bicarbonate chloride dioxide The essential reaction here is: (H30)+ + (HCO3)- ^2 H2O + CO2. The carbon dioxide produced in this reaction raises the bread. Baking soda is often added to sour milk in making bread. In this case, the lactic acid in the sour milk replaces the acid-forming salt in the baking powder. The salts generally used in baking powders are NaAl(S04)2 CaHP04 KHC4H4O6 sodium aluminum sulfate (sometimes erroneously called alum but more often referred to as S.A.S.) calcium acid phosphate potassium acid tartrate (cream of tartar) Perspiration deodorants generally consist of solutions of aluminum chloride or sulfate, or iron chloride or sulfate. These salts hydrolyze to form acids which deodorize the odor-producing substances accompanying perspiration under the arm, and also act as non-perspirants. The "foamite" type of fire-extinguisher uses alum, KA1(S04)2 • 12 H2O, which hydrolyzes to form an acid solution which will liberate carbon dioxide upon contact with sodium bicarbonate. Soap and such detergents as borax, trisodium phosphate, and sodium carbonate owe their detergent action in part, at least, to the basic properties of their water solutions. These substances are salts of strong bases and weak acids and therefore hydrolyze to form basic solutions.
THE TRANSFER OF PROTONS 609 A detergent is a material which cleans by chemical action rather than by solvent action or mechanical means. Oranges produce a basic reaction in the human body, although they are definitely acid in nature, because the excess citric acid, being an organic compound, is burned up in the body to form carbon dioxide and water and is thus eliminated, while the sodium salts in the orange juice, being salts of a strong base with a weak acid, hydrolyze to form basic solutions. Certain substances, called buffers, are very important in maintaining a nearly constant hydronium-ion concentration in the human body. An excess or deficiency of hydronium ions results in disorders which are generally described as acidosis, alkalosis, or hyper- and hypo-acidity. Buffer substances must be able to neutralize both acids and bases. Disodium phosphate is a good buffer substance; inasmuch as it is an acid salt, it will neutralize bases, and inasmuch as it will accept protons, it will neutralize acids. Proteins are capable of reacting with either acids or bases and thus act as buffers, but inasmuch as they are altered somewhat in these reactions and also because they are the substances from which living tissue is made, it is obvious that this reserve should not be overworked. Baking soda is an excellent buffer substance; it will react with acids and is therefore often taken internally to relieve acid indigestion. Baking soda acts as an acid because it is an acid salt ; and it acts as a base because it accepts protons to form a weakly electrovalent covalent compound. STUDY QUESTIONS 1. Define neutralization and illustrate with some examples. 2. Define hydrolysis and illustrate with some examples. 3. What types of salts hydrolyze, and why? 4. Explain the action of baking powders. 5. How may one tell when an acid solution is just neutralized by addition of a solution of a base? 6. Why do all soaps produce a basic reaction when they are dissolved in water? 7. What is a buffer substance? Give an example. 8. Why does acid orange juice act as a base in the body? 9. Explain the action of the foamite type of fire-extinguisher. 10. Why are buffer substances of importance in the human body? What types of substances act as buffers in the human body? 11. What are the ingredients in the "S.A.S." type of baking powder? 12. Explain the action of indicators. 13. Why is baking soda a good perspiration deodorant?