First stage inorganic chemistry / by G.H. Bailey ; edited by William Briggs.

  • Bailey, G. H.
Date:
[1896]
Catalogue details

Licence: Public Domain Mark

Credit: First stage inorganic chemistry / by G.H. Bailey ; edited by William Briggs. Source: Wellcome Collection.

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    The former experiment affords can example of the method of investigating- composition by separation into simpler constituent parts, i. e. by analysis, and the latter that of reproducing a sub- stance by bringing together the constituent parts, i. e. by synthesis. How the chemical identity of two substances is estab- lished.—From these experiments we also gather that two sub- stances are regarded as identical from a chemical poinFof view when on being exposed to heat or oflief agenciesroTlo the action of chemical re-agents, they exhibit like changes of composition. This being the case then, notwithstanding certain differences of outward appearance, texture, and cohesive power, we regard calcite ^ and the white powder above mentioned as chemically identical substances. Similarly lampblack and diamond, though as unlike in form, hardness, and colour as two substances well can be, are yet chemically identical. For if we burn lampblack and diamond in a sufficient supply of oxygen, the product in both cases consists entirely of carbon dioxide. Also if we burn equal weights of lampblack and diamond, the weight of the carbon dioxide formed in the one case is precisely the same as that formed in the other. Changes of composition brought about by the action of chemical agents on lampblack in all cases corre- spond to those effected on diamond, and the chemical identity of lampblack with diamond is thus established. Physical properties of matter as distinguished from chemical properties. — Properties such as lustre, hardness, tenacity, and state of aggregation, are classed as purely physical; they affect matter according to the circumstances of pressure and temperature, etc., under which the body exists, and as these alter, so the physical state or condition of the body is liable also to alter. This change of physical state is not accompanied by change of weight or composition. The distinction between the physical and chemical changes in matter is of such importance that we append other examples which serve to throw light upon it. Exp. 5.—A small fragment of iodine.is placed in a test-tube and gently warmed ; presently, violet vapours rise, and the whole of 1 Marble and crystals of aragonite may be examined by the student, these being also chemically identical with calcite.