Bitumen 1428 (from pitch; or from a pine, because it flows from the pine tree,) called also asphaltos,pissasphaltus, asphaltum, bitumen Judaicum, carabe funerum, gummi funerum, mumia, car vise ok Sodon, fossile pitch, and Jews' pitch.

It is a solid mineral substance, of a dusky colour on the outside, and a deep shining black within; having but little taste or smell, except it is heated, in which case it emits a strong pitchy odour. It is not soluble in oils, nor in vinous spirits; it melts but imperfectly in the fire.. On burning it a large quantity of ashes remain. It is found in the earth in many parts of Egypt, and floating on the surface of the Dead Sea. At first it is soft, but grows hard by keeping.

Though we have spoken of bitumen as a single substance, we are, from the labours of Mr. Hatchet and Mr. Kirwan enabled now to be more correct and discriminate. Bitumens are either fluid or solid. Of the former we have the pure naphtha and petroleum: of the latter, the mineral tar and pitch, and asphaltum. The first by exposure to the air gradually becomes darker, till from naphtha it is changed to a true asphaltum, the substance to which the synonyms at the head of the article apply. The amber is a bituminous substance also, though from a different source.

Bitumens, like oils, are composed of hydrogen, car-bone, and azote, modified in some measure by oxygen. To carry on the analogy with the substances of the vegetable kingdom which they resemble, we may suppose the two extremities of the scale, naphtha and asphaltum, to be the ethereal oils and resins. It is indeed highly probable that all bitumens are of vegetable origin (Hatchet, .Phil. Transactions, for 1805, part ii. and Nicholson's Journal, vol. ii.). Naphtha, the purest of the bitumens, is lighter than water, viz. 0.788: the smell highly penetrating, though not disagreeable, like oil of amber. It resists the cold ofo of Fahrenheit. The petroleum is less fluid, transparent, and agreeable, specific gravity 0.878. Mineral tar, dark coloured, viscid, and of an unpleasing smell; scarcely if at all heavier than water. Mineral flitch, brittle in cold weather, dark and opaque; gravity nearly that of water. Asphaltum, very brittle and shining, fusible and inflammable', specific gravity often 1.165.

These seemingly differ only in their proportion of oxygen. In medicine, the first kind has been employed as a stimulant and an antispasmodic, but is now disused. It is employed externally only in chilblains and paralytic affections: and what is styled British oil is drawn from stone coal. Naphtha has been employed in hectics, but is too stimulating, and produces considerable inconvenience. It is found very pure, near the Caspian Sea, at Backu. Seepetroleum and Succinum.

Bitumen Barbadense. See Pissaelkum.

Bitumen Liquidum. See Petroleum.