PETROLEUM

PETROLEUM, or ROCK OIL; a thick oily substance exuding out of the earth, and collected on the surface of wells in many parts of the world. It is found on some in Italy, and in a deserted mine in the province of Dalame in Sweden. In this last place it collects itself in small hollows of limestone, like resin in the wood of the pine-tree. It is found trickling from the rocks, or issuing from the earth, in many parts of the duchy of Modena, and in various parts of France, Switzerland, Germany, and Scotland, as well as in Asia. It is also found not only on the surface of wells as already mentioned, but mixed with earth and sand, from whence it may be separated by infusion in water. It is of a pungent and acrid taste, and smells like the oil of amber, but more agreeable. It is very light and very pellucid; but, though equally bright and clear under all circumstances, it is liable to a very great variety in its colour. It is naturally almost colourless, and in its appearance greatly resembles the most pure oil of turpentine: this is called subite petroleum, though it has no more colour than water. It is sometimes tinged of a brownish, reddish, yellowish, or faint greenish colour; but its most frequent colour is a mixture of the reddish and blackish, in such a degree that it looks black when viewed behind the light, but purple when placed between the eye and a candle or window. It is rendered thinner by distillation with water, and leaves a resinous residuum; when distilled with a volatile alkali, the latter acquires the properties of succinate ammonia, and contains the acid of amber. It is the most frequent of all the liquid bitumens, and is perhaps the most valuable of them all in medicine. It is to be chosen the purest, lightest, and most pellucid that can be had, such as is of the most penetrating smell and is most inflammable. Monet informs us that some kinds of it are of the density of nut-oil. It is insoluble in spirit of wine; which, though it be the great dissolvent of sulphur, has no effect upon petroleum, not even with ever so long a digestion. It will not take fire with the dephlegmated acid spirits; as oil of cloves and other of the vegetable essential oils do; and in distillation, either by balneum marie or in sand, it will neither yield phlegm nor acid spirit; but the oil itself, rises in its own form, leaving in the retort only a little matter, thick as honey, and of a brownish colour. The finer kinds resemble naphtha. Kirwan is of opinion that naphtha is converted into petroleum by a process similar to what takes place in essential oils when exposed to the atmosphere; in which case the oil absorbs not only the pure, but also the phlogisticated, part of the atmosphere, in consequence of which several alterations take place in them. Mr Bouldoc made several experiments with the white petroleum of Modena; an account of which he gave to the Paris academy. It easily took fire (a) on being brought near a candle, and that without immediately touching the flame; and when heated in any vessel it will attract the flame of a candle, though placed at a great height above the vessel; and the vapour it sends up taking fire, the flame will be communicated to the vessel of heated liquor, and the whole will be consumed. It burns in the water; and when mixed with any liquor swims on the surface of it, even of the highest rectified spirit of wine, which is 4th heavier than pure petroleum. It readily mixes with all the essential oils of vegetables, as oil of lavender, turpentine, and the rest, and seems very much of their nature: nor is this very strange, since the alliance between these bodies is probably nearer than is imagined, as the essential oils of vegetables may have been originally mineral ones, and drawn up out of the earth into the vessels of the plants. The distinguishing characteristic of the petroleum is its thickness, resembling inspissated oil: when pure it is lighter than spirit of wine; but, though ever so well rectified, it becomes in time thick and black as before. Petroleum, when shaken, yields a few bubbles; but they sooner subside than in almost any other liquor, and the liquor resumes its clear state again almost immediately. This seems owing to the air in this fluid being very equally distributed to all its parts, and the liquor being composed of particles very evenly and nicely arranged. This extensibility of the oil is also amazing. A drop of it will spread over several feet of water, and in this condition it gives a great variety of colours; that is, the several parts of which this thin film is composed act as so many prisms. The most severe frost never congeals petroleum into ice; and paper wetted with it becomes transparent as when wetted with oil; but it does not continue so, the paper becoming opaque again in a few minutes as the oil dries away. There are three varieties of it according to Mongez. 1. The yellow, found at Modena in Italy; very light and volatile. 2. The reddish, or yellowish red; some of which is collected at Gabian in Languedoc and in Alsace. 3. The heavy, black, or brown kind, which is the most common, and met with in England, France, Germany, and some other countries. It generally runs out either from chinks or gaps of rocks, or is mixed with the earth, and gushes out of it; or it swims on the water of some fountains, as already mentioned. According to Dr Lippert, a kind of resin is produced by mixing petroleum with smoking nitrous acid. The taste of this substance is very bitter, but the smell resembles that of musk. The vitriolic acid, according to the same author, produces a resin still more bitter, but without any aromatic smell. Cronstedt enumerates the following species. 1. Maliba, or Barbadoes tar, a thick substance resembling soft pitch. It is found in several parts of Europe and Asia; particularly Sweden, Germany, and Switzerland; on the coast of the Dead Sea in Palestine; (a) Alfonso Barba, in his book of metals, gives a very melancholy instance of the power of petroleum of taking fire at a distance. He tells us, that a certain well, yielding petroleum on the surface of its water, being to be repaired, the workman took down into the well with him a lantern and a candle in it: there were some holes in the lantern, through which the petroleum at a considerable distance sucked out the flame of the candle, and, taking fire, burst up with the noise of a cannon, and tore the man to pieces. Petroleum. Palestine; in Persia, in the chinks of rocks, and in strata of gypsum and limestone, or floating upon water. It is found also in America, and at Colebrookdale in England. Kirwan tells us, that petroleum exposed for a long time to the air forms this substance. It is of a viscous consistency; and of a brown, black, or reddish black colour. Sometimes it is inodorous, but generally of a more or less disagreeable smell, particularly when burned. It melts easily, and burns with much smoke and foot, leaving either ashes or a slag according to the heterogeneous matter it contains. It contains a portion of the acid of amber. It gives a bitter salt with mineral alkali, more difficult of solution than common salt, and which, when treated with charcoal, does not yield any sulphur. II. Elastic Parol; a very singular kind of fossil met with in some parts of England. This, in colour and consistency, exactly resembles the CAOUTCHouc, or elastic gum-resin, commonly called Indian rubber, found in South America, and used for rubbing out the traces of black lead pencils from paper. It is of a dark brown colour, almost black; and in some pieces has a yellowish-brown cast like the same gum-resin. It can scarcely be distinguished from the caoutchouc with regard to its elastic property, excepting that the cohesion of its parts is not so great. It burns with a smoky flame, and melts likewise into a thick oily fluid; but emits a disagreeable smell like the Fossil Pitch or Barbadoes tar. "On the whole (says M. Petrolenz, Magellan), this fossil seems to confirm the opinion of those mineralogists who believe that these oily combustibles derive their origin from the vegetable kingdom. It seems worth trying whether pieces of asphaltum, buried in damp beds of sparry rubbish or other kinds of earth, would take the same elastic consistency." This substance was found in the year 1785 near Cassleton in Derbyshire, but in very small quantities. Some of the specimens were of a cylindrical form, like bits of small branches or stalks of vegetables; tho' much more flexible, being perfectly elastic. III. Hardened rock-oil, or fossil pitch, an inflammable substance dug out of the ground in many parts of the world, and known by the names of petroleum induratum, pix montana, indenpech, berghartz, &c. There are two species. 1. The asphaltum (a), or pure fossil pitch, found on the shores of the Dead Sea and of the Red Sea; also in Sweden, Germany, and France: See ASPHALTUM. It is a smooth, hard, brittle, inodorous substance, of a black or brown colour when looked at; but on holding it up betwixt the eye and the light, appears of a deep red. It swims in water; breaks with a smooth and shining surface; melts easily; and, when pure, burns without leaving any ashes; but, if impure, leaves ashes, or a slag. M. Monet asserts that it contains sulphur, or at least the vitriolic acid. It is slightly and partially acted upon by spirit-of-wine and (a) This species is found in great quantity in a bituminous lake or plain in the island of Trinidad, of which Mr Anderson gives the following copious account in the 79th volume of the Philosophical Transactions. "A most remarkable production of nature in the island of Trinidad, is a bituminous lake, or rather plain, known by the name of Tar Lake; by the French called La Bray, from the resemblance to, and answering the intention of, ship-pitch. It lies in the leeward side of the island, about half-way from the Boes to the south end, where the mangrove swamps are interrupted by the sand-banks and hills; and on a point of land which extends into the sea about two miles, exactly opposite to the high mountains of Paria, on the north side of the gulf. "This cape, or headland, is about 50 feet above the level of the sea, and is the greatest elevation of land on this side of the island. From the sea it appears a mass of black vitrified rocks; but, on a close examination, it is found a composition of bituminous scoria, vitrified sand, and earth, cemented together: in some parts beds of cinders only are found. In approaching this cape, there is a strong sulphureous smell, sometimes disagreeable. This smell is prevalent in many parts of the ground to the distance of eight or ten miles from it. This point of land is about two miles broad, and on the east and west sides, from the distance of about half a mile from the sea, falls with a gentle declivity to it, and is joined to the main land on the south by the continuation of the mangrove swamps; so that the bituminous plain is on the highest part of it, and only separated from the sea by a margin of wood which surrounds it, and prevents a distant prospect of it. Its situation is similar to a savannah, and like them, it is not seen till treading upon its verge. Its colour and even surface present at first the aspect of a lake of water; but it is possible it got the appellation of Lake when seen in the hot and dry weather, at which time its surface to the depth of an inch is liquid; and then from its cohesive quality it cannot be walked upon. "It is of a circular form, about three miles in circumference. At my first approach it appeared a plain, as smooth as glass, excepting some small clumps of shrubs and dwarf trees that had taken possession of some spots of it; but when I had proceeded some yards on it, I found it divided into areolæ of different sizes and shapes: the chasms or divisions anastomosed through every part of it; the surface of the areolæ perfectly horizontal and smooth; the margins undulated, each undulation enlarged to the bottom till they join the opposite. On the surface, the margin or first undulation is distant from the opposite from four to six feet, and the same depth before they coalesce; but where the angles of the areolæ oppose, the chasms or ramifications are wider and deeper. When I was at it, all these chasms were full of water, the whole forming one true horizontal plane, which rendered my investigation of it difficult and tedious, being necessitated to plunge into the water a great depth in passing from one areolæ to another. The truest idea that can be formed of its surface will be from the areolæ and their ramifications on the back of a turtle. Its more common consistency and appearance is that of pit-coal, the colour rather greyer. It breaks into small fragments of Petroleum and other. Besides the countries above-mentioned, Brunnich informs us that the asphaltum comes from Porto Principe in the island of Cuba in the West Indies. It is likewise found, according to Fourcroy, in many parts of China; and is used for a covering to ships by Arabs and Indians. 2. The pie montana impura contains a great quantity of earthy matter, which is left in the retort after distillation, or upon the charcoal if burnt in the open fire. It coheres like a slag, and is of the colour of black-lead; but in a strong heat this earth is soon volatilised, so that its nature is not yet well known. During the distillation a liquid substance falls into the receiver, which is found to be of the same nature with rock-oil. The substance itself is found in Sweden and several other countries. The pisasphaltum is of a mean consistence between the asphaltum and the common petroleum. Mongez says that it is the same with the bitumen collected from a well named De la Pege, near Clermont Ferrand in France. The people of mount Ciaro, in Italy, have some years since found out a much easier way of finding petroleum than that which they formerly had been used to. This mountain abounds with a sort of greyish salt, which lies in large horizontal beds, mingled with strata of clay, and large quantities of a spar of that kind called a cellular appearance, and glossy, with a number of minute and shining particles interspersed through its substance; it is very friable, and, when liquid, is of a jet black colour. Some parts of the surface are covered with a thin and brittle scoria, a little elevated. "As to its depth, I can form no idea of it; for in no part could I find a substratum of any other substance: in some parts I found calcined earth mixed with it. "Although I smelt sulphur very strong on passing over many parts of it, I could discover no appearance of it, or any rent or crack through which the steams might issue; probably it was from some parts of the adjacent woods: for although sulphur is the basis of this bituminous matter, yet the smells are very different, and easily distinguished, for its smell comes the nearest to that of pitch of any thing I know. I could make no impression on its surface without an axe: at the depth of a foot I found it a little softer, with an oily appearance, in small cells. A little of it held to a burning candle makes a hissing or crackling noise like nitre, emitting small sparks with a vivid flame, which extinguish the moment the candle is removed. A piece put in the fire will boil up a long time without suffering much diminution: after a long time's severe heat, the surface will burn and form a thin scoria, under which the rest remains liquid. Heat seems not to render it fluid, or occupy a larger space than when cold; from which, I imagine, there is but little alteration on it during the dry months, as the solar rays cannot exert their force above an inch below the surface. I was told by one Frenchman, that in the dry season the whole was an uniform smooth mass; and by another, that the ravine contained water fit for use during the year. But neither can I believe: for if, according to the first assertion, it was an homogeneous mass, something more than an external cause must affect it to give it the present appearances; nor without some hidden cause can the second be granted. Although the bottoms of these ramified channels admit not of absorption, yet from their open exposure, and the black surface of the circumjacent parts, evaporation must go on amazingly quick, and a short time of dry weather must soon empty them; nor from the situation and structure of the place is there a possibility of supply but from the clouds. To show that the progress of evaporation is inconceivably quick here, at the time I visited it there were, on an average, two-thirds of the time incessant torrents of rains; but from the afternoon being dry, with a gentle breeze (as is generally the case during the rainy season in this island), there evidently was an equilibrium between the rain and the evaporation; for in the course of three days I saw it twice, and perceived no alteration on the height of the water, nor any outlet for it but by evaporation. "I take this bituminous substance to be the bitumen asphaltum Linnei. A gentle heat renders it ductile; hence, mixed with a little grease or common pitch, it is much used for the bottoms of ships, and for which intention it is collected by many; and I should conceive it a preservative against the borer, so destructive to ships in this part of the world. "Besides this place, where it is found in this solid state, it is found liquid in many parts of the woods; and at the distance of 20 miles from this about two inches thick in round holes of three or four inches diameter, and often at cracks or rents. This is consequently liquid, and smells stronger of tar than when indurated, and adheres strongly to any thing it touches; grease is the only thing that will divert the hands of it. "The soil in general, for some distance round La Bray, is cinders and burnt earths; and where not so, it is a strong argillaceous soil; the whole exceedingly fertile, which is always the case where there are any sulphureous particles in it. Every part of the country, to the distance of 30 miles round, has every appearance of being formed by convulsions of nature from subterranean fires. In several parts of the woods are hot springs; some I tried, with a well-graduated thermometer of Fahrenheit, were 20° and 22° hotter than the atmosphere at the time of trial. From its position to them, this part of the island has certainly experienced the effects of the volcanic eruptions, which have heaped up those prodigious masses of mountains that terminate the province of Paria on the north; and no doubt there has been, and still probably is, a communication between them. One of these mountains opposite to La Bray in Trinidad, about 30 miles distant, has every appearance of a volcanic mountain: however, the volcanic efforts have been very weak here, as no traces of them extend above two miles from the sea in this part of the island, and the greater called by the Germans scalenites; which is the common sort, that ferments with acids, and readily dissolves in them, and calcines in a small fire. They pierce these slates in a perpendicular direction till they find water; and the petroleum which had been dispersed among the cracks of those slates is then washed out by the water, and brought from all the neighbouring places to the hole or well which they have dug, on the surface of the water of which it swims after eight or ten days. When there is enough of it got together, they ladle it from the top of the water with brass basons; and it is then easily separated from what little water is taken up with it. These wells or holes continue to furnish the oil in different quantities for a considerable time; and when they will yield no more, they pierce the slates in some other place. It is never used among us as a medicine; but the French give it internally in hysterical complaints, and to their children for worms: some also give it from 10 to 15 drops in wine for suppression of the menses. This, however, is rather the practice of the common people than of the faculty.