Introduction to Inorganic Chemistry
Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III COMBINING PROPORTIONS BY WEIGHT If we now return to the illustrations of chemical phenomena which we have been studying (pp. 14-21), we shall find a new question arising naturally out of them. This is, whether the mass of the materials is altered, as are the other attributes, in these chemical changes. Conservation of Mass: Fourth Characteristic of Chemical Change. ? The most painstaking chemical work seems to show that, if all the substances concerned in the chemical change are weighed before and after the change, there is no evidence of any alteration in the quantity of matter. The two weights, representing the sums of the constituents and of the products respectively, are, indeed, never absolutely identical, but the more careful the work and the more delicate the instrument used in weighing,
...the more nearly do the values approach identity. We are able to state, therefore, as a law of all chemical phenomena, that: The mass of a system is not affected by any chemical change within the system. This statement simply means that th e great law of the conservation of mass holds true in chemistry as it does in physics. Chemical changes, thoroughgoing as they are in res pect to all other qualities, do not affect the mass; an element carries with it its weight, entirely unchanged, through the most complicated chemical transformations. A law, as we have seen (p. 45), is a condensed statement describing some constant mode of behavior. It is simply a summary of our experience. As such, it is subject to modification when a fact is discovered with which it conflicts. Thus, it is perfectly possible that we may yet find cases of demonstrable changes in weight accompanying other physical or chemical changes in a limited system. Indeed, it has more than once been alleged ...
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