ADVERTISEMENT.

A class book that should comprehend in regular order, the text of what is delivered in lectures, and what is expected from the candidate at examination, is a thing altogether so desirable for Professor and Student, that I had contemplated the compilation of such a work for the use of my pupils in this University, when, very opportunely, I received Mr. Brande's Manual. Having perused this well arranged outline of a course of Chemistry, I deemed iny projected undertaking unnecessary: and yet, I could not adopt his book, nor recommend it to my class entirely in the shape he gives it. The atomic theory, as delivered by him, differs considerably from the view I take of it; and, as I hold this to be the exceptionable part of Mr. Brande's otherwise excellent performance, it only remained for me to change, or as I would fain say, amend it, in that particular. It is easily seen that his specific gravities and atomic weights are frequently inaccurate: nor is the error, perhaps, entirely accidental. Representative numbers recently determined in a very satisfactory manner are still given by Mr. Brande as they were represented five or six years ago, although Dr. Prout, but more especially Dr. Thomson has demonstrated that they required correction. The latter has clearly proved that the atoms of the simple bodies nitrogen, oxygen, chlorine, carbon, sulphur, phosphorus, iodine, are even multiples of the weight of an atom of hydrogen. He has also shown that when hydrogen is made the unity of weight, and oxygen the unity of specific gravity, then the weight of the atom of a gaseous body is either equal to the specific gravity, or some multiple of the same by a whole number.

If the specific gravity of oxygen be 1, that of hydrogen will be 0.0625, which × by 2 = 0.125, weight of the atom of hydrogen. In most cases of this kind the atomic weight is double the specific gravity; in a few, however, twice 2 is found to be the proper multiplier: the reason of this difference is not very obvious; but in the first the combination is most energetic. See the table added, p. 161.

In consequence of these views, the representative numbers for the elementary and compound atoms, throughout the whole work, have been altered to correspond with the results of the latest discoveries and improvements. Almost all the notes, likewise, are additions; In other respects, and wherever the investigations of Mr. Brande himself are given as authority, the text has suffered no change. But intending the manual only for a class book and text of my lectures, 188 pages of preface have been left out and 102 pages of index abridged to two. The first, though well composed, could, in this instance, be the better spared, as it is but an enlarged, though in several particulars, an improved version of the author's earlier dissertation on the progress of chemical science, of which an edition from the Boston press must be already known to the American reader. A wish to avoid making the publication too voluminous to be read in connexion with other studies, or rendering the price too high for beginners, induced me to retrench what was, in some measure, unnecessary; and, applying to myself the same rule, I forbear to lengthen this advertisement.

New-York, Nov. 20, 1821.

THOUGH the following pages are chiefly intended for students, it is trusted that the proficient will find them a useful compendium of Chemistry.

The arrangement of the materials differs from that sanctioned by our best elementary writers, but it has been adopted in consequence of some years' experience of its advantages in teaching the principles of the science.

In the first chapter, the leading facts connected with the general laws of chemical changes are discussed under the separate heads of Attraction, Heat, and Electricity. The second chapter relates to the properties of Radiant Matter, and its influence upon the composition of bodies. In the third and fourth chapters I have de⚫tailed the sources and properties of the Simple Supporters of Combustion, and of the Elementary Acidifiable Substances, and their mutual combinations. The fifth chapter contains an account of the Metals, and of their compounds with the bodies previously described, and with each other.

The sixth chapter embraces such details respecting the Assay and Analysis of Metalliferous Compounds, as are necessarily omitted under the individual history of the metals: in this division of the book I have availed myself largely of the invaluable analytical labours of Klaproth, and have selected from other sources such instances as I conceived best adapted to assist the student in acquiring correct notions of this department of chemical study; the processes detailed have, with few exceptions, been submitted to the test of experimental repetition in the laboratory of the Royal Institution, and those which have not been thus verified, are drawn from sources of the highest authority.

In the seventh chapter I have aimed at a succinct description of the means of analyzing mineral waters, and as their examination is frequently desirable where the conveniences of a regular laboratory are not attainable, I have subjoined a short account of the tests and apparatus required in this branch of research.

Upon the subject of analysis in general, the student will find inexhaustible information in the writings of Klaproth, and in the Essays of Vauquelin; the former have only been in part translated into the English language; and the latter are scattered through various periodical publications, especially the Journal des Mines, and the Annales de Chimie. The last thirty volumes of the Philosophical Transactions are also rich in detached essays, by our most eminent chemists, illustrative of the art of analysis. A judicious selection from these sources upon an extended scale would be truly valuable to the practical chemist, and would materially contribute to facilitate the progress of our analytical inquiries.

For general directions concerning the art of analysis, and for many useful and original hints relative to the manipulations of the laboratory, I have much satisfaction in referring to Mr. Children's translation of the fourth volume of M. Thenard's Traite de Chimie. reader will observe, that in Chapter VI. I have availed myself of this work, which the student will do well to consult in detail.

The

The eighth and ninth chapters are assigned to Vegetable and Animal Products; and the concluding chapter contains the heads of Geological inquiry.

In the Appendix to this work will be found Ta bles, chiefly useful as presenting a synoptic view of most of the simple and compound bodies, with their represen tative or equivalent numbers; these may easily be trans ferred to a logometric scale, as recommended by Dr Wollaston, who has thus furnished the laboratory with one of its most useful implements.

The principal materials of this book have been drawı from the notes that I have employed in my differen courses of lectures, and these are partly original, and partly compiled from various sources; although there fore I have in most intances scrupulously referred to the authorities quoted, it is possible that this may have beer sometimes omitted, and for such omissions, I now beg to