BIR

B I S

76

Birdlime thus prepared is greenish, bitter,very tenacious, spinning out into threads whendrawn asunder, and smelling somewhat likelinseed oil. When a thin layer is spread out onglass and exposed for some time to light and airit dries, turns brown, and is then no longer vis-cous, even when again wetted, but may beground to powder. It reddens litmus. Whenbirdlime is heated without addition, it melts intoa pasty mass, swells, becomes full of bubbles,smelling like heated oil, and if put upon heatedcoals, or when red hot, it burns with much flameand dense black smoke. It continues to burnwhen once lit, till it is entirely reduced to anash, which is white and very alkaline.

Water boiled upon birdlime has little or noaction upon it except to render it rather morefluid, and to dissolve out a portion of acid (whichis shewn by the water reddening litmus) and alittle mucilage and extract.

But caustic potash acts very powerfully uponbirdlime. A strong lye of potash boiled withbirdlime forms a white magma which on evapo-ration turns brown, hardens, and acquires thesmell and taste of soap. This soap dissolvesin alcohol and water, and is decomposed byacids like the common soaps.

Sulphuric acid blackens and carbonizes bird-lime, and on adding lime the smell of vinegar isperceived.

Nitric acid heated on birdlime converts it toa hard brittle mass, which when treated withmore of the same acid, is partly changed tooxalic and malic acid, and partly to a yellowwax-like resin, soluble in potash and in alcohol.

Birdlime long shaken in concentrated oxy-muriatic acid becomes white, loses its viscidityand is broken into hard compact masses, stillenclosing a portion of the unchanged birdlime.

Acetous acid softens birdlime and dissolves aportion. Carbonat of potash does not disturbthis solution, and when evaporated to dryness itleaves a residue resembling the resins, but whichcannot be perfectly dried.

Boiling alcohol dissolves birdlime. The solu-tion is of a clear yellow when hot, but becomesturbid on cooling, and deposits a yellow matterlike wax, whilst the clear liquor remains bitter,nauseous, acid, and leaves a kind of resin whenevaporated.

Sulphuric ether totally dissolves birdlime, andwith more ease than any other reagent. Thesolution is greenish, yellow and acid. Whenmuch water is added, an oil separates and comesup to the surface, which much resembles lin-seed oil, and will form a compound like plasterwhen boiled with litharge. The ethereal solu-

tion of birdlime when evaporated leaves a yel-low soft matter like wax All these facts shewthe analogy of birdlime with oily or resinoussubstances, and its entire difference from vege-table gluten.

BISMUTH.

1. Native. Its primitive form, according t»Hauy is the regular octohedron; and the onlyother crystal that he mentions as belonging tothis species, is an acute rhomboid, the alternateangles of which are 60° and 120°.

Besides the three species of ores described inthe article Bismuth in this Dictionary, there ar*certain natural mixtures- probably, rather thancombinations, of metals in which bismuth isthe predominating ingredient, and which there-fore may be mentioned here.

1. Bismuth with Copper and Sulphur.

This substance was discovered by Selb in the

cobalt mine of Neugluck, in the district ofFurstenberg. Its colour is steel-grey, by ex-posure to the air becoming bluish and reddish;has a slightly metallic lustre, a fine grainedfracture, is soft and semi-ductile. Accordingto Klaproth , it is composed of47.24 Bismuth34.66 Copper12.58 Sulphur

94.48

2. Argentiferous Bismuth.

Its colour is a pale lead-grey becoming darkeron exposure to the air ; it is generally dissemi-nated, rarely in mass. It melts easily beforethe blowpipe. It occurs at Schatzlach, in theBlack forest, and according to Klaproth , iscomposed of the following ingredients.

33. Lead27. Bismuth15 . Silver4.3 Iron0.9 Copper16.3 Sulphur

96.5

3. Nadelerz.

Its colour is steel grey verging more or lessto copper red, but generally is dull, and super-ficially yellow or green from decomposition. Itoccurs disseminated, or crystallized in striatedacicular hexahedral prisms, often curved, some-times articulated, and always implanted. Itslongitudinal fracture is lamellar with a splendentmetallic lustre. It is soft, semiductile, and itsspecific gr. is about 6.1. It occurs in Siberia in white quartz mixed with native gold.