BITTER PRINCIPLES BITUMEN 671 is a harsh qua-ak; their flight slow and heavy, with their long legs outstretched behind. Their habits are nocturnal ; their haunts Least Bittern (Ardetta exilis). fresh-water pools, stagnant rivers, and mo- rasses; they build, like the heron, in trees, ordinarily raising two young ones. Their food is small fish, lizards, frogs, and frog spawn, of which they are voracious consumers. They are good eating in September, when the first frosts are commencing, and are eaten roasted, with currant jelly and stuffing, like the hare, which they somewhat resemble. BITTER PRINCIPLES, substances extracted from plants by digestion in water, alcohol, or ether, and which possess in concentrated form that which gives the bitter taste to plants. Excepting this, these extracts do not appear to possess other characteristic properties in com- mon; their nature, however, is not very well understood. Many alkaloids, especially quinia and strychnia, possess an intense bitterness, but are not classified with the substances just described, because they possess other much more important properties. Some bitter prin- ciples are crystallizable, as colombine, quas- sine, gentiopierine, taraxacine, aloine, and phloridzine, a substance obtained from the bark of the apple, pear, and cherry ; while the bitters of hops, pinkroot, and wild cherry have not yet been obtained in crystals, and that of the last mentioned drug not even isolated. Some of the numerous varieties of bitters are soluble in water ; some only in alcohol or ether. They are generally neutral in their properties, uniting neither with acids nor bases. Bitters are used -in medicine as tonics, and also as aperients; and in the manufacture of malt liquors they are employed to impart to them their bitter flavor. In the healthy condition bitters do not assist or accelerate digestion, but rather the contrary, as has been shown by direct experiment. When the digestion is en- feebled, however, they seem to impart vigor to this process by stimulating the flow of gastric juice and by retarding the progress of ab- normal fermentations, which have a tendency 95 VOL. n. 43 to take the place of and interrupt the healthy process. The sensation produced by the irrita- tion of bitters in the stomach should not be mistaken for true hunger. B1TTOOR. See BITHOOE. BITUMEN, a generic name for a variety of substances found in the earth, or exuding from it upon the surface, in the form of springs. The liquid varieties become inspissated by ex- posure, and eventually harden into the solid form, which is asphaltum. The bitumens burn with a flame and thick black smoke, giving out the peculiar odor called bituminous. Some of the impure fluid bitumens, and the solid vari- ety when melted, closely resemble coal tar. They are distinguished from bituminous coal in giving no ammonia, or mere traces of it, by distillation, and in developing negative elec- tricity by friction without being insulated; also, when ignited upon a grate, the bitumens melt and run through at the temperature of about 220 F., but the coals burn to ashes. In melting, volatile fluids escape from them with no swelling up other than that due to ebulli- tion. This property of dividing by heat into Uuids and solid residues having a porous form, assimilates the bitumens to ordinary turpen- tine and tar, and renders them unsuitable for producing gas economically. In boiling water the bitumens soften, adhere to the sides of the vessel, and give off naphtha; coal undergoes no change. The bitumens, again, dissolve per- fectly in spirits of turpentine, benzole, rosin oil, linseed oil, and sulphuric ether ; while coal, after long digestion in the oils, only colors the liquid brown, and to the sulphuric ether im- parts a naphtha-like fluid and a resinous body. The bitumens decompose nitric acid, coal does not; they combine with sulphuric acid, coal is not affected by it. Dropped upon melted tin with a temperature of 442 F., the bitumens decompose and give off copious fumes ; coal is unaltered. Most of these points of difference were given in evidence by Dr. A. A. Hayes and Dr. 0. T. Jackson of Boston, in an impor- tant suit tried in New Brunswick, to test the title to the Albert coal-mining property, this turning on the point whether the product was coal or asphaltum. Dr. Dre notices that the fluid bitumens differ from coal tar in not pro- ducing the six substances extracted from the latter by Mr. Mansfield, and named by him alliole, benzole, toluole, camphole, mortuole, and nitro-benzole. The varieties of bitumen commonly described are : the liquid oil, naph- tha, or, in its more impure form, petroleum ; the viscid pitchy bitumen, which passes into the black resinous asphaltum ; and the elastic bitumen, or elaterite of the mineralogists. The last is also called mineral caoutchouc, from its property of rubbing out pencil marks. It was first found in the deserted lead mine of Odin, in Derbyshire, England, by Dr. Lister, in 1673, and was called by him a subterranean fungus. It occurs in soft flexible masses of blackish brown colors and resinous lustre, and consists
