The origin of bitumen is as little known as that of most of the productions of nature. Some regard it as an empyreumatic oil, a matter analogous to liquid resin or essential oil, resulting from the destruction of that astonishing multitude of animals and vegetables buried in the earth, whose solid remains are daily brought to view in mineral researches. It has been also supposed that naphtha and petroleum are the product of coals decomposed either by the fire of volcanos, by the subterranean combustion of coal itself, or by the decomposition of pyrites. The latter opinion is not supported by any direct evidence, but the two former are sufficiently probable.
Elastic Bitumen is a rare substance, found hitherto only near Castleton, in Derbyshire, in fissures of slaty clay.
Bituminous mastic, or cement, has been of late extensively employed in France for covering roofs and terraces, and lining water cisterns. The mineral bitumen used for the composition of this mastic is procured chiefly from the Obsann (Bas-Rhin), from the Parc (department de l’Ain), and from the Puy-de-la-Poix (department of Puy-de-Dome). But boiled coal-tar answers equally well. In the neighbourhood of these localities, there is a limestone impregnated with bitumen, which suits for giving consistence to the cement. This is well dried, ground to powder, sifted, and stirred while hot, in about one fifth its weight of melted asphaltum, contained in a cast-iron boiler. Dry chalk or bricks, ground and sifted, will suit equally well. As soon as this paste is made quite homogeneous, it is lifted out with an iron shovel or spoon, and spread in rectangular moulds, secured with pegs at the joints, fastened to a kind of platform of smoothed planks, covered with strong sheet-iron. The sides of these moulds should be previously smeared over with a thin coat of loam-paste, to prevent their adhesion to the mastic. Whenever the cake is cold, the frame is taken asunder, and it is removed from the iron plate by an oblong shovel, or strong spatula of iron. These cakes or bricks are usually 18 inches long, 12 broad, and 4 thick, and weigh about 70 lbs.
BITTER PRINCIPLE. (Amère, Fr.; Bitterstoff, Germ.) This principle has not been insulated hitherto by the chemist from the other proximate principles of plants, but its existence is sufficiently recognised by the taste. The following list contains the principal bitter substances, many of which have been used in the arts and in medicine.
| Name. | Part employed. | Country. | Observations. | ||
|---|---|---|---|---|---|
| Quassia | Wood | Surinam, E. Indies | Powerfully bitter | ||
| Wormwood | Herb | Great Britain | Ditto | ||
| Aloe | Inspissated juice | South Africa | Ditto | ||
| Angustura | Bark | South America | Ditto | ||
| Orange | Unripe fruit | South of Europe | - | Aromatic bitter | |
| Ditto | Peel | Ditto | |||
| Acorus | Root | Ditto | Ditto | ||
| Carduus Benedictus | Herb | Greek Archipelago | |||
| Cascarilla | Bark | Jamaica | Ditto | ||
| Centaury | Herb | Great Britain | |||
| Camomile | Flowers | ||||
| Colocynth | Fruit | Levant | Intolerably bitter | ||
| Colombo | Root | East Africa | Very bitter | ||
| Fumitory | Herb | Great Britain | |||
| Gentiana lutea | Root | Switzerland | Very bitter | ||
| Ground Ivy | Herb | Great Britain | |||
| Walnut | Peels | With tannin | |||
| Island moss | With starch | ||||
| Hops | Scales of the female flowers | Great Britain | Aromatic bitters | ||
| Milfoil | Herb flowers | Great Britain | |||
| Large-leaved Satyrion | Herb | Great Britain | |||
| Rhubarb | Root | China | Disagreeable odour | ||
| Rue | Herb | Great Britain | Bitter and sharp | ||
| Tansy | Herb flowers | Ditto | Bitter and offensive | ||
| Bitter trefoil | Herb | Ditto | |||
| Simarouba | Bark | Guyana | |||
| Bryony | Root | Great Britain | Sharp, bitter, nauseous | ||
| Coffee | Seeds | Arabia | |||
BLACK DYE. (Teinte noire, Fr. Schwartze farbe, Germ.) For 1 cwt. of cloth, there are put into a boiler of middle size 18 lbs. of logwood, with as much Aleppo galls in powder, and the whole, being enclosed in a bag, is boiled in a sufficient quantity of water for 12 hours. One-third of this bath is transferred into another boiler with two pounds of verdigris; and the stuff is passed through this solution, stirring it continually during two hours, taking care to keep the bath very hot without boiling. The stuff is then lifted out, another third of the bath is added to the boiler, along with eight pounds of sulphate of iron or green vitriol. The fire is to be lowered while the sulphate dissolves, and the bath is allowed to cool for half an hour, after which the stuff is introduced, and well moved about for an hour, after which it is taken out to air. Lastly, the remaining third of the bath is added to the other two, taking care to squeeze the bag well. 18 or 22 lbs. of sumach are thrown in; the whole is just brought to a boil, and then refreshed with a little cold water; two pounds more of sulphate of iron are added, after which the stuff is turned through for an hour. It is thereafter washed, aired, and put again into the bath, stirring it continually for an hour. After this, it is carried to the river, washed well, and then filled. Whenever the water runs off clear, a bath is prepared with weld, which is made to boil for an instant; and after refreshing the bath the stuff is turned in to soften, and to render the black more fast. In this manner, a very beautiful black is obtained, without rendering the cloth too harsh.
Commonly more simple processes are employed. Thus the blue cloth is simply turned through a bath of gall-nuts, where it is boiled for two hours. It is next passed through a bath of logwood and sulphate of iron for two hours, without boiling, after which it is washed and fulled.
Hellot has found that the dyeing might be performed in the following manner:—For 20 yards of dark blue-cloth, a bath is made of two pounds of fustic (morus tinctoria), 41⁄4 lbs. of logwood, and 11 lbs. sumach. After boiling the cloth in it for three hours it is lifted out, 11 lbs. of sulphate of iron are thrown into the boiler, and the cloth is then passed through it during two hours. It is now aired, and put again in the bath for an hour. It is, lastly, washed and scoured. The black is less velvety than that of the preceding process. Experience convinced him that the maddering prescribed in the ancient regulations only gives a reddish cast to the black, which is obtained finer and more velvety without madder.
A black may be dyed likewise without having given a blue ground. This method is employed for cloths of little value. In this case they are rooted; that is to say, they receive a dun ground with walnut husks, or the root of the walnut tree, and are afterwards made black in the manner above described, or in some other way; for it is obvious that a black may be obtained by several processes.
According to Lewis, the proportions which the English dyers most generally adopt are, for one hundred and twelve pounds of woollen cloth previously dyed of a dark blue, about five pounds of sulphate of iron, as much gall-nuts, and thirty pounds of logwood. They begin by galling the cloth, they then pass it through the decoction of logwood, to which the sulphate of iron has been added.