Syn. Bitume (F.), Erdharze (G.), Bitume (I.), Bitumen (S).

In the limited signification of this term, it is meant to imply those mineral inflammable bodies which resemble, in a certain degree, oily and resinous substances. They have been divided into two classes : the first containing bitumens, or, properly speaking, bituminous oils, which possess nearly the same properties as the essential oils; the second, bitumens, strictly so called, which possess properties peculiar to themselves'3; and a third class may be formed of those substances in which bitumen predominates with other components.

According to Hatchett, the elements of bitumens are carbon, hydrogen, sometimes azote, and probably oxygen.4

1 Thomsons Chymistry, 5th edit. vol. i. p. 459.

2 An alloy composed of 8 parts of Bismuth, 5 of lead, and 3 of tin, will melt in water below the temperature of 212°; and is rather useful for taking casts and similar purposes.

3 Thomson's Chymistry, 5th edit. vol. ii. p. 384.

4 Linn. Trans, iv. 129.

Officinal. Petroleum Barbadense, Lond. Bitumen Petroleum, Edin. Petroleum Barbadense, Dub. Petroleum. Barbadoes Tar. Syn. Petrole (F.), Steinohl (G.), Bergolja (Swed.), Petrolio (I.), Neft(Arab),

Mitti tel (H.), Munty lun (Tarn.), Minnia tanna (Malay), Ippoo (Sumatran),

Kesosonoabra (Japanese).

The officinal names imposed by the three British colleges are not to be regarded as synonymous of the same species of bitumen. The first species of the bituminous oil is properly named by the London College, the second variety of that species being the real Petroleum of the shops; but the Dublin College has incorrectly given the second species of the proper bitumens as the synonyme of Bitumen Petroleum.

Bitumen is found in many parts of the world, in various states of purity. When free from foreign ingredients, and before it has been long exposed to the action of the air, it is named naphtha; of which the purest kind that is brought to Europe comes from Monte Ciaro, near Piacenza, in Italy. "This hill consists of horizontal beds of argillite, in which pits are sunk till the water comes in; after which the naphtha oozes out of the sides and floats on the surface of the water, whence it is skimmed off every week."1 It usually flows from rocks of the coal formation.2 There is also a fountain of very pure naphtha at the base of the mountains of Buck-tiavi, between the city of Bruster and the valley of Ramhov-mouz. The less pure petroleum of the shops is procured from Monte Pestino, near Modena. In the Birman empire there are 520 wells in one district, which yield annually more than 400,000 hogsheads of petroleum.

Qualities. - Naphtha is colourless, or of a pale yellowish colour, thin, fluid, light, transparent, odoriferous, unctuous to the touch, volatile, and very inflammable: it consists of 36.72 carbon, and 5.00 hydrogen. By long exposure to the air it passes into the second variety, petroleum; which is thicker than naphtha, unctuous to the feel, semi-transparent, of a reddish or blackish brown colour, and when long exposed to the air changes into true bitumen. It has a strong, penetrating, not disagreeable odour, and a bitter, pungent, acrid taste; and is not quite so inflammable as naphtha. The sp. gr. of naphtha is 0.753 to 0.847: that of petroleum varies from 0.730 to 0.878.3 Both are insoluble in water; but soluble in alcohol, ether, the volatile and the fixed oils. When distilled with water, petroleum comes over nearly as clear and fluid as naphtha. Both these varieties of bitumens combine with fat, resins, essential oil, and camphor: with alkalies they form soapy compounds; and sulphuric and nitric acids change them into solid resins.

1 Mem. Sci. 1736, p. 57.; quoted by Aikin, Dict, of Chym. art. Bitumen.

2 In Zante there are several pitch springs, which were as productive 2300 years ago as they are now.

3 Kirwan.

Medical properties and uses. - Petroleum is a stimulating antispasmodic and sudorific; and as such has been given in asthma and coughs unattended with inflammation; and in Germany has been extolled as a specific for tape-worm; but it is chiefly used externally as a stimulant in diseases of the hip-joint, in rheumatic and other chronic pains, in chilblains, porrigo, and to paralytic limbs, applied by friction.1 It is, however, scarcely ever employed; and on this account is not often to be procured in the shops. The dose of petroleum may be from x. to f 3 ss. given in any convenient vehicle.