Elements of chemistry, in two volumes / by John Murray.

  • Murray, John.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry, in two volumes / by John Murray. Source: Wellcome Collection.

    132/768 (page 120)
    conceived, is due to the latter circumstance; for the com- bining weights of metals are higher than those of other simple bodies, and, in general, the combining weights of the heavier metals are greater than those of lighter metals. Thus gold is one of the heaviest of the metals, and its atomic weight is one of the largest. To this principle, however, there are many exceptions, which ‘sufficiently prove that much also is to be attributed to the first cause, that of cohesion, in explaining the greater specific gravity ol the substances of this class. Opacity so far belongs to the metals, that when in the thinnest plates into which they can be reduced without the continuity being broken, they transmit no light, while the most opaque substance of any other class becomes trans- lucent under a similar mechanical division. The only ex- ception, perhaps, with regard to the metals, is afforded by gold, which, in very thin leaves, transmits a green light; this, however, may perhaps be owing to fissures in it when reduced to such a state of tenuity. The opacity of the metals, and the closeness of their texture, cause them to reflect the greater part of the light which falls on their surface : they hence possess a high de- gree of lustre or brilliancy. Many of them lose this from the tarnish they suffer from exposure to the air; but in their fresh fracture they all exhibit it. It is increased al- so by the high polish of which they are in general sus- ceptible. The property of tenacity or strong cohesion of parts, appears in the metals under two forms, ductility and mal- leability. By the former is understood that modification of tenacity whence a body can be drawn into fine wire . by the latter, that in consequence of which it can be beat or extended into thin leaves. Though both properties