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THE PHILOSOPHY

OF

EXPERIMENTAL CHEMISTRY.

PART XV.

OF METALS.

1. The metals are distinguished by certain obvious and physical properties; as,

1. Lustre. The brilliancy which the metals possess, is known by the name of metallic lustre. This property is occasioned by their reflecting much more light than any

other bodies, which seems to depend on the closeness of their texture.

2. Opacity. Metals are perfectly opaque, or impervious to light. Newton observed, that goid leaf zkázy of an inch thick, when held between the eye and the light appears of a lively green, and, according to him, transmits the green coloured rays. Silver leaf, however, toodoo of an inch thick, is completely impervious to light. Metals are therefore considered opaque.

3. Fusibility. That metals may be melted by the application of heat, is a well known property. They still retain their opacity. The metals, however, differ

B

in their fusibility. Thus, mercury remains fluid in the common temperature of the atmosphere, and even requires intense cold to make it solid; while other metals, as platinum, cannot be melted except by the most violent heat.

4. Weight. The specific gravity of the metals is exceedingly various. The greater number of them are heavier than any other known substances.

Several of the new metals, discovered by Mr. Davy, are not so heavy as water. Thus plantinum is 23 times heavier than water, whilst the specific gravity of potassium is only 0.6, that of water being 1.

5. They are all conductors of electricity.

6. They possess different degrees of hardness; and the ingenuity of the artist has rendered some of them considerably hard by artificial means. Hence the numerous instruments made of steel.

7. Elasticity. This property depends upon the hardness of the metal, and may be increased by the same process by which their hardness is increased.

8. Malleability. The capacity of being extended and flattened when struck with a hammer, is called malleability. This is a useful property of the metals. All metals do not possess it in the same degree. Heat increases it remarkably.

9. Ductility. The capacity of being drawn out into wire, by means of a certain contrivance, is called ductility. This property is also wanting in some of the metals.

10. Tenacity. Tenacity is the power which a metallic wire, of a given diameter, has of resisting, without breaking, the action of a weight suspended from its extremity. Ductility depends, in some measure, on this property. The metals differ in this capacity. An iron wire, for instance, bth of an inch in diameter, will support a weight of 500 pounds. A lead wire, on the contrary, of the same diameter, will not support above 29lbs.

II. The metals at present known, including those discovered by Mr. Davy, amount to 40. Twelve of these are imperfectly known, and some philosophers

have expressed their doubts of their existence. As these metals have been obtained from the alkalies and earths, we have noticed them when treating of these substances. We have to consider, therefore, the remaining metals, which are 28 in number. Seven of these were known to the ancients, and seventeen have been discovered since the year 1730.

In the arrangement of the metals, Thomson has adopted the following, in four classes, each of which is characterised by some general property.

[blocks in formation]

Those of the first class, by way of eminence, were formerly considered perfect metals, and all the

rest were called semi-metals or imperfect metals. But this distinction is disused.

The metals as they are found, are generally mineralized, by the union of sulphur, oxygen, &c. forming ores. The ores of metals have been classified or arranged in several ways.

The following arrangement of ores, is adopted by professor Cooper.* Metallic Fossils.

Black silver
I. GENUS PLATINA. Glance silver
Native platina

Brittle
II. OR GOLD GENUS. Red silver ore
Native gold

Dark
Gold yellow

Light
Brass yellow

White silver ore
Grayish yellow

Black silver ore
Nagyag

*Gray silver ore Graphic

V. OR COPPER GENUS. III. QUICKSILVER GENUS. Native copper Native quicksilver

Vitreous Natural amalgam

Compact *Fluid

Foliated *Solid

Variegated ore Corneous ore

Copper pyrites
Hepatic ore

White copper ore
Compact

Grey copper ore
Slaty

Black copper
Cinnabar

Red copper ore
Dark red common

Compact
Bright red fibrous

Foliated
IV. SILVER GENUS.

Capillary
Native silver

Tile ore *Common

Earthy *Goldish

Indurated Antimonial silver

Copper azure Arsenical silver

Earthy Bismuthal

Radiated
Corneous ore

Malachite
Common

Fibrous
Earthy

* Introductory Lecture, 8vo.p. 218.

Compact
Copper green
Iron shot copper

Green
Earthy

Slaggy
Olivine ore
SCopper mica
Copper emerald
VII. OR IRON GENUS.
Native iron
Iron pyrites

Common
Radiated
Hepatic
Capillary

*Magnetic Magnetic iron stone

Compact (common)

Iron sand
Iron glance
(Specular)

Common
Compact
Foliated

Micaceous
Red iron stone

Red iron froth
Red iron ochre
Compact

Red hematite
Brown iron stone

Brown ochre
* Frothy
Ochry
Compact

Hematitic
Sparry iron stone
Black iron stone

Compact

*Hematitic Clay iron stone

Reddle
Columnar
Granular
*Lenticular
*Jaspery
Common
Kidney

Pea ore
Bog ore

Morass
Swamp

Meadow
Blue iron earth
Green iron earth
Emerilt

VII. OR LEAD GENUS.
Lead Glance

Common

Compact
Blue lead ore
Brown
Black
White
Green
Red
Yellow
Native vitriol of lead
Lead earth

Coherent
*Friable
VIII. OR TIN GENUS.
Tin pyrites
Tin stone
Cornish ore
IX. or BISMUTH GENUS
Native
Glance
Ochre

[graphic]
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