instruction imparted by lectures or by the study of textbooks of theoretical chemistry, and practical instruction imparted in a chemical laboratory by working according to the directions of a practical text-book. Since by this system the student has time and opportunity afforded him for the study of the theoretical and descriptive portions of the science, it is as unnecessary as it is undesirable that his Practical Text-book should tempt him to bestow valuable time in the laboratory upon the study of matters of theoretical-not practical-importance. The analytical reactions and methods have been carefully worked through from the text by myself and by the members of my classes: the accuracy and intelligibility of their descriptions have thus, I hope, been secured; only those reactions and methods which are commonly employed for analytical purposes have been entered. I have naturally, in selecting analytical methods for an elementary treatise, felt it desireable that those chosen should be as simple and easy of execution as possible; in some cases, however, methods which are most eligible on these grounds have proved on trial to be so inferior in accuracy and delicacy, that they have been abandoned in favour of others which are recommended by their reliability rather than by their simplicity. In such cases, however, I have also described the more simple methods, since they may be employed in analyses, in which minute quantities of a substance have not to be tested for. The reactions given in an elementary text-book have necessarily been limited as to number, and I have felt it in general adviseable to introduce such reactions as are useful in general analysis rather than those which claim to be merely interesting and instructive. The book has been divided into seven sections, the contents of which are fully stated on pages ix.-xv. The first six contain a good practical course for senior students; this may however be modified to suit junior students, or those working with a special object, as is shown in the Introduction. The seventh section contains full lists of all apparatus, re agents, and chemicals required in working through the different sections; there is also added a list of general apparatus, with a description when necessary of its construction and use. In this section there will also be found full and systematic descriptions of the most simple methods for preparing the different solutions required in analysis, with a statement of the strength most appropriate for each. Experience has proved that these are matters which merit more attention than is usually bestowed upon them. The methods of preparing pure chemicals are omitted, since they may now be readily and cheaply purchased; before using purchased chemicals their purity should, however, always be ascertained by the tests given in this section. : Symbolic notation has been employed, instead of the full chemical names, throughout the sections on analytical chemistry in its most concise form this chemical shorthand conduces so much to brevity in writing down results that no other plea is required for its use. The simple plan of labelling each bottle in the laboratory with the chemical formula as well as the name of its contents, will prevent any difficulty arising from this general employment of chemical formulæ. Special features in the book are the arrangement of all Tables across instead of along the pages; the turning of the book is thus rendered unnecessary—a convenience which will be appreciated by all students of Practical Chemistry. The "Tables of Differences," which contain for each Analytical Group a summary of the differences of behaviour of its members with reagents, are also special-being an extension of the system employed in Galloway's "Manual of Qualitative Analysis." It is almost superfluous to mention that free use has been made of the standard works of Fresenius and Rose: much valuable information has been introduced from these sources. I have also frequently adopted the very convenient tabular form of entering analytical methods which is employed in Valentin's "Text-book of Practical Chemistry," and with the author's permission have transcribed, with a few trivial alterations, the excellent Phosphate Table devised by him. My acknowledgments are also due to Dr. W. A. Tilden of Clifton College and to the Rev. T. N. Hutchinson of Rugby, and to many other teachers who have suggested valuable improve ments. The book is especially intended to furnish a course of instruction in practical chemistry in the laboratories of our public and other schools. It will thus supply a demand which is rapidly increasing, as the value of a sound elementary instruction in practical science is becoming more widely appreciated, both as a means of mental training and as a preparation for the chemical and medical professions, as well as for many branches of manufacturing industry and enterprise. The fifth section has been inserted for the use of those who are specially preparing for practical examinations in which proficiency in the analysis of simple salts only is required of the candidate. This is the standard fixed for the Preliminary Scientific (M.B.) Examination of the London University, and for the more elementary examinations in the Oxford University, such as those for school certificates and open scholarships. The sixth section, however, contains additional details suited for the higher analytical work of advanced students, and will be found sufficient to qualify a student for the higher examinations in analytical chemistry, such as the B.Sc. Honours Examination in the London University. The introduction as appendices into this edition of the reactions and methods of detection of the rarer elements, and of the use of the spectroscope with a spectrum chart, will, it is believed, render the book more useful to advanced students. F. C. NEWCASTLE-UNDER-LYME, November 1876. |