Descrizione:
Vwiat classification of the principles of chemistry shall be adopted depends on what is now taken to be the purpose of the science. An examination of the progress of chemistry at different times, in the light of the knowledge we have to-day, seems to me to show that the main purpose of the science has always been the same. Chemistry has concerned itself in the past, as it concerns itself now, with the changes of material things; and, although the aspects of this study have been as varied as those of the transmutations of matter wherewith it deals, the essential object of the study, at all times, may be expressed in the language of to-day as being to describe, to set in due order, and to connect the changes of composition and the changes of properties which occur simultaneously in systems of homogeneous substances, and the conditions under which these changes proceed. The history of the advances which have been made towards attaining this object is the history of the principles of chemistry. The actions of our surroundings on our senses are spoken of as the properties of substances. If all the properties, except, it may be, the masses of any portions of a substance obtained by sifting or sorting that substance are the same. |
