Excerpt from A Dictionary of Chemistry and the Allied Branches of Other Sciences, Vol. 5 of 5: Quadrantoxide-Zymurgy HE nine years which have elapsed since this work wascommenced have witnessed important changes in the modes of viewing and representing the constitution of chemical compounds. The old system of notation, founded on the dualistic theory of chemical combination, and the atomic weights adopted in Gmelin's Handbook and other standard works ofolder date, may now be regarded as belonging to the past; and even the new system introduced by Gerhardt has undergone considerable modifica tion, the atomic weights which that chemist assigned to many of the metals having been doubled, and his system of typical representation having been developed into the modern theory of atomicity. These changes and de velopements are explained in the article classifica'hon by Profesor G. 0. Foster, and the articles Ammo weights, and metals, Aromc Wmoa'rs 41m classification or, by Dr. Odling. The smaller atomic weights of many of the metals Hg 100; Zn having been adopted in the earlier part of the Dictionary, it was thought advisable, in first introducing the larger ones, to distinguish them by doubled symbols (bba 187, t 200, but in the latter part of the work these double symbols, which are rather clumsy, have been abandoned, and the ordinary symbols used, with accents or dashes, when necessary, to indicate the equivalent value. 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.