CONTENTS
CHAP. PAGE [ PREFACE] v [I. INTRODUCTION] 1 [II. SULPHURIC ACID AND SULPHATES] 10 [III. NITRIC ACID AND NITRATES] 28 [IV. THE HALOGEN ACIDS] 43 [V. CARBONIC ACID AND CARBONATES] 49 [VI. PHOSPHORIC, BORIC, AND SILICIC ACIDS] 56 [VII. ORGANIC ACIDS] 67 [VIII. MILD ALKALI] 80 [IX. CAUSTIC ALKALIS] 95 [X. ELECTROLYTIC METHODS] 101 [ INDEX] 109
ILLUSTRATIONS
FIG. PAGE [BACTERIA NODULES ON THE ROOT OF LUPIN] Frontispiece [1. DIAGRAM] 7 [2. PLAN OF SULPHURIC ACID WORKS] 13 [3. GENERAL VIEW OF SULPHURIC ACID WORKS] 15 [4. SULPHUR TRIOXIDE—THE CONTACT PROCESS] 19 [5. PREPARATION OF NITRIC ACID] 30 [6. NITROGEN CYCLE (DIAGRAM)] 38 [7. NITRIC ACID FROM AIR (DIAGRAM)] 41 [8. PREPARATION OF HYDROCHLORIC ACID] 45 [9. BORIC ACID] 59 [10. QUICK VINEGAR PROCESS] 71 [11. DUTCH PROCESS FOR WHITE LEAD] 74 [12. SALT CAKE FURNACE] 83 [13. BLACK ASH FURNACE] 85 [14. THE SOLVAY PROCESS] 89 [15. THE ELECTROLYSIS OF SALT SOLUTION] 102 [16. THE CASTNER PROCESS] 105
ACIDS, ALKALIS, AND SALTS
CHAPTER I
INTRODUCTION
Acids. A vague hint from Nature gave mankind the first indication of the existence of acids. The juice pressed from ripe grapes is a sweetish liquid. If it is kept for some time, the sweetness goes, and the liquid acquires a burning taste. If kept still longer, the burning taste is lost, and in its place a sharp acid flavour, not entirely displeasing to the palate, is developed. The liquid obtained in this way is now called wine vinegar; the particular substance which gives it its characteristic taste is acetic acid.
The strongest vinegar does not contain more than 10 per cent. of acetic acid, which is itself a comparatively weak acid. It is, therefore, not a very active solvent. Nevertheless, for metals and for limestone rock, and other substances of a calcareous nature, its solvent power is greater than that of any other liquid known at the time of its discovery. It was this property which seems to have appealed most strongly to the imagination of the early chemists; and, as is very often the case, the description of its powers was very much exaggerated. Livy and Plutarch, who have given us an account of Hannibal’s invasion of Italy by way of the Alps, both gravely declare that the Carthaginian leader cleared a passage for his elephants through solid rocks by pouring vinegar over them!
In the Middle Ages, the study of Chemistry was fostered mainly as a possible means whereby long life and untold riches might be obtained. The “Philosopher’s Stone,” by the agency of which the base metals were to be changed to gold, and the “Elixir of Life,” which was to banish disease and death, were eagerly sought for. Though these were vain imaginings according to modern ideas, nevertheless they were powerful incentives towards experimental work. Many new substances were discovered in this period, and among these were nitric acid (aqua fortis), hydrochloric acid (spirit of salt), and sulphuric acid (oil of vitriol).
Acids were then valued above all other substances. The mediaeval chemist (or alchemist, as he was called) clearly saw that unless a body could be dissolved up there was no hope of changing it. Nitric acid, therefore, which, in conjunction with hydrochloric acid, dissolved even gold itself, was very highly esteemed. Oil of vitriol also was scarcely less important, for it was required for the production of other acids.