PROFESSOR OF CHEMISTRY, THE JAMES MILLIKIN UNIVERSITY; AND ALBERT L. SMITH, PH.D. INSTRUCTOR IN CHEMISTRY, THE ENGLEWOOD HIGH SCHOOL Copyright, 1912. BY JOHN C. HESSLER. MIA OL AIMBORLIA The Fort Hill Press SAMUEL USHER 176 TO 184 HIGH STREET BOSTON, MASS. PREFACE. The Revised Edition of the “Essentials of Chemistry" retains the scientific character of the original text, but the method of treatment and the order of topics have been modified in accordance with the experience of the past ten years. These years have brought about significant changes in the Chemistry courses of secondary schools. Not only has the number of students increased greatly, but chemical science has become more and more important as a prerequisite for work in the other sciences and in applied courses. In view of this increased and altered demand for chemical instruction, authors are tempted to neglect the basic principles of the science, and to enlarge upon the purely descriptive matter. But Chemistry that is merely descriptive is not an adequate preparation even for applied courses. What is sought of Chemistry, both by those who study it as a prerequisite for other work, and by those whose sole aim is general culture, is, essentially, the chemical point of view. To present that point of view properly, a text-book must include a correct, even if simple, treatment of chemical theory. Especially 251954 |