Excerpt from The Principles of Theoretical Chemistry: With Special Reference to the Constitution of Chemical Compounds The science of chemistry has to deal with everything connected with the deepest-seated changes in composition which the different forms of matter undergo. The first observations, and for a long time the only observations, made on chemical changes were qualitative. The fact that a substance A when brought in contact with a substance B gives the substance C or the substances C and D was noted; but very little, if anything, more was learned re garding the change. During this qualitative period a great many facts were discovered, many new substances were brought to light, and general methods of preparation for certain classes of compounds were devised. Toward the end of the last century the researches of Lavoisier made it clear to chemists that in studying chem ical changes it is necessary to take into account not only the nature of the substances which are involved in reao tions, but also the quantities of these substances. Thus the quantitative period of chemistry was begun. Since then chemists have paid special attention to the weights of the substances with which they worked, and it is largely due to this that the science has advanced so rapidly during the last hundred years. It was soon shown that certain laws underlie all chemical changes, and the recognition of these laws proved of the greatest assistance in the further study of the changes.14 principles OF theoretical chemistry. The first law of general application that was recognized was the law of the indestructibility of matter. It was found as the result of many observations that the sum of the masses of the products of a chemical change is always exactly equal to the sum of the masses of the substances which act upon one another. Nothing is gained or lost in the operation. This law, like every other law of nature, is simply a statement of what has been found to be true in every case that has been studied, and its statement implies that a large number of cases have been studied. Since its truth was first recognized an almost infinite number of observations have confirmed it in the most striking way. As regards the question whether it is possible to conceive of a state of things in which the law of the indestructibility of matter would not hold good we have nothing to do. It may be said, however, that the law could not have been discovered without the aid of many quantitative chemical experiments. It is an expression of facts established. It is not an axiom. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.