Elements of chemistry

Front matter

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Preface

It is hardly necessary for the author of the following volume to make any excuses for its publication, since, notwithstanding the multiplicity of books on the same subject, there seems to be none, which are exactly adapted to the object for which this is principally designed. The Conversations on Chemistry, and the works of Parke and Joyce, besides the interlocutory form in which they are written, are objectionable, in not containing the recent discoveries and improvements in the science ; and the volume of Dr. Turner, though free from these objections, is too large for the use of schools and academies.

In this volume, it has been the intention of the author, not only to avoid these objections, but, at the same time, to explain the elements and doctrines of the science in sufficient detail, to give a competent knowledge of its several parts, and in such language as can be understood by those who will but read the book attentively, and pursue the subject in course.

It appears to the writer, that in teaching Chemistry to youth, its elementary parts have not been sufficiently in-

VI PREFACE.

sisted on at the beginning. Of all the sciences, this is the most complete, in respect to its language, the order of its arrangement, the succession of its subjects, and consequently, in the facility with which it may be learned. But from these perfections, arises the absolute necessity of becoming well acquainted with its first principles, before the student can derive and retain any useful knowledge from its study. The nomenclature of chemistry, the laws of affinity, and the doctrine of proportions, are far more necessary to a proper knowledge of this science, than is a knowledge of mathematics to the study of Astronomy. The cause of an eclipse, or the reason why the complicated motions of the earth should produce a change of seasons, can be fully understood without the use of mathematics. But without a knowledge of affinity, and proportions, the decomposition of a salt, or the formation of a definite compound, are absolutely incomprehensible phenomena ; nor can they be explained without a previous acquaintance with the peculiar language of chemistry.

It is from a conviction of the importance of first principles in learning this science, that the author has devoted so much attention to the imponderable agents, attraction, affinity, and galvanism, and to the explanation of definite proportions and chemical equivalents.

The doctrine of definite proportions, being now universally adopted, forms one of the fundamental principles of chemical science. And whether the theory of atoms, which accounts for the facts on which this doctrine is founded, be true, or false, the doctrine itself will ever maintain its integrity, its elements being nothing more than the expression of facts which experiment and analysis have developed. The subject of proportions, independently of its relation to the theory or practice of Chemistry, is highly curious, and of uncommon interest, both to the naturalist

PREFACE. Vli

and the moral philosopher. To the first it shows, that the laws of nature are equally inherent and efficient, in dead and in animated matter, and that the effects of these laws are as peculiar and distinctive in the formation of chemical compounds, as thej are in the production and habitudes of the different races of animals. To the moralist, this subject teaches, that nothing has been formed by the fortuitous concurrence of atoms, but that even the "stocks and stones" bear the impress of creative agency and design — that the air he breathes, and the water he drinks, are formed of invariable proportions of certain elements, and that these compounds are so precisely adapted to his nature and wants, that the least change in the proportion of their constituents would inevitably effect his destruction.

Besides the charms which this subject presents to the reflecting student, the composition of compound bodies, in recent books of chemistry, is expressed in equivalent numbers, and therefore cannot be understood without a knowledge of the doctrine of proportions. The author, therefore, before the description of each element and compound, has affixed to its name, at the head of the sections, its combining number, or atomic weight. By this arrangement, the pupil, at a single glance, becomes acquainted, not only with the scientific, and common names, but also with the composition and proportions of all the compounds described.

In respect to the authorities which have been consulted in the composition of this work, the principal are, Dr- Thomson, Dr. Henry, Sir H. Davy, Mr. Gray, Dr. Ure, Mr. Accum, Mr. Faraday, the Library of Useful Knowledge, the Journal of the Loyal Institution, Silliman's Journal, and Dr. Turner.

Of the work of the latter author, free use has been made, his. arrangement of subjects, with some variations, having been adopted, and his exposition of the doctrine of proportions carefully consulted. The work now offered, is not, however, to be considered as a servile compilation ; the former experience of the author as a lecturer, and his habit, for many years, of analysing various substances, having given him opportunities, not only of verifying the deductions of others, but occasionally of making new experiments for himself.

Hartford, Conn. February, 1846.

CHEMISTRY,

1. Chemistry is that science which investigates the composition and properties of bodies, and by which we are enabled to explain the causes of the natural changes which take place in material substances.

Natural Science has been divided into two great branches, the one comprehending all those natural changes which are accompanied by sensible motions ; the other including all those natural changes accompanied by insensible motions. The first science is called Natural Philosophy ; including also the Philosophy of Mechanics, and the laws of motion. The second is known under the name of Chemistry, or Chemical Philosophy.

As a science, Chemistry is of the highest importance to mankind, since, by its investigations, the practical arts are constantly improving.

All chemical knowledge is founded on analysis and synthesis, that is, the decomposition of bodies, or the separation of compounds into their simple elements, or the recomposition of simple bodies into compounds.

When water is passed through a red hot iron tube, in the form of steam, it is decomposed ; its oxygen uniting with the iron, while its hydrogen passes away in a state of freedom, or may be collected and retained. This is called analysis ; and the bodies so separated from each other, if they cannot again be decomposed, are called elements. Thus hydrogen and oxygen are the elements of water. When oxygen, which may be obtained pure, as will be seen in another place, is burned with hydrogen, a quantity of water will be formed. This is called synthesis, or the recomposition

What is Chemistry ? How is science divided ? What is the foundation of all chemical knowledge ? What is analysis ? What is synthesis T 1*

10 IMPONDERABLE AGENTS.

of water from its elements. Thus, all knowledge of this science is obtained by experiment.

As a science, chemistry is intimately connected with a great variety of natural phenomena. All satisfactory explanation of the causes of rain, hail, dew, wind, earthquakes, and volcanoes, have been given by the aid of chemical knowledge. The phenomena of respiration, the decay and growth of plants, and the functions of the several parts of animals, are also explained in a satisfactory manner, only by the aid of chemistry.

As an art, chemistry is connected, more or less intimately with nearly every branch of human industry, and particularly with agriculture and manufactures. In its application to agriculture, chemistry furnishes the most direct and certain means of ascertaining what a barren soil wants to make it a fruitful one, and also what ingredient any soil requires to best adapt it to any given kind of produce. Many of our most common and useful articles are manufactured entirely by chemical processes. The making of soap, glass, bleaching salts, the several kinds of acids, and almost every kind of medicine, depend wholly on the manipulations of chemistry. The art of the potter, ironsmith, tanner, sugar-maker, distiller, brewer, vintner, papermaker, and painter, are also connected in various degrees with chemistry.

Natural objects may be separated into two great divisions, or classes, viz. ; Imponderable agents and Ponderable bodies.