Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. THE HYDROGEN AND HYDROXYL IONS. § 20. Acids, Alkalies and the Hydrogen and Hydroxyl Ions.—Soluble chlorides have the common property of precipitating silver chloride from silver solutions, because they have the common ion Cl'. Acids are dissociated electrolytically in solution, as indicated by their being electrolytes and by their abnormally depressing the freezing point. Their common properties must therefore be referred to their common ion. The acidity of hydrogen chloride indicates that this common ion is that of hydrogen. The chlorine ion certainly does not confer acid properties on its solution, and there only remains the hydrogen ion. All acids are known to contain hydrogen, and an investigation of the reactions into which they enter, confirms the belief that they are characterised by their hydrogen ions when in solution. This confirmation is the more complete, inasmuch as not only can the reactions of acids be shown to be connected with the presence of hydrogen ions, but their strengths are found to be proportional to the extent of their dissociation. For instance, hydrochloric and acetic acids are dissociated according to the equations— HCl Z H ' + Cl' CH3 COOH Z H + CH, COO'. Acetic acid is undoubtedly a weaker acid than hydrochloric acid. Hydrochloric acid will prevent the precipitation of calcium oxalate, for example, while acetic acid will not. The two equilibrium equations can, as usual, be represented by— KHCl Z H x Cl' and K2CH3 COOH Z CH3COO' x H when the symbols HCl, etc., represent the respective concentrations. Conductivity experiments show that Kj is greater than K2. This means that the concentration of the hydrogen ions is greater in a solution of hydrochloric acid than in a solution of acetic acid of the same concent...