The History of Chemistry (Vol.1&2). Thomas Thomson

Чтение книги онлайн.

СКАЧАТЬ The vulgar notion that the ancients did not know that water will always rise in pipes as high as the source from which it proceeds, and that it was this ignorance which led to the formation of aqueducts, is quite unfounded. Nobody can read Pliny without seeing that this important fact was well known in his time.

      Sheet lead was also used in the time of Pliny, and applied to the same purposes as at present. But lead was much higher priced among the ancients than it is at present. Pliny informs us that its price was to that of tin as 7 to 10. Hence it must have sold at the rate of 6s. 0¼d. per pound. The present price of lead does not much exceed three halfpence the pound. It is therefore only 1–48th part of the price which it bore in the time of Pliny. This difference must be chiefly owing to the improvements made by the moderns in working the mines and smelting the ores of lead.

      Tin, in Pliny’s time, was used as a solder for lead. For this purpose it is well adapted, as it is so much easier smelted than lead. But when he says that lead is used also as a solder for tin, his meaning is not so clear. Probably he means an alloy of lead and tin, which, fusing at a lower point than tin, may be used to solder that metal. The addition of some bismuth reduces the fusing point materially; but that metal was unknown to the ancients.

      Argentarium is an alloy of equal parts of lead and tin. Tertiarium, of two parts lead and one part tin. It was used as a solder.

      Some preparations of lead were used by the ancients in medicine, as we know from the description of them given us by Dioscorides and Pliny. These preparations consisted chiefly of protoxide of lead and lead reduced to powder, and partially oxidized by triturating it with water in a mortar. They were applied to ulcers, and employed externally as astringents.

      Molybdena was also employed in medicine. Pliny says it was the same as galena. From his description it is obvious that it was litharge; for it was in scales, and was more valued the nearer its colour approached to that of gold. It was employed, as it still is, for making plasters. Pliny gives us the process for making the plaster employed by the Roman surgeons. It was made by heating together 3 lbs. molybdena or litharge, 1 lb. wax, 3 heminæ, or 1½ pint, of olive oil. This process is very nearly the same as the one at present followed by apothecaries for making adhesive plaster.

      Psimmythium, or cerussa, was the same as our white lead. It was made by exposing lead in sheets to the fumes of vinegar. It would seem probable from Pliny’s account, though it is confused and inaccurate, that the ancients were in the habit of dissolving cerussa in vinegar, and thus making an impure acetate of lead.

      Cerussa was used in medicine. It constituted also a common white paint. At one time, Pliny says, it was found native; but in his time all that was used was prepared artificially.

      Cerussa usta seems to have been nearly the same as our red lead. It was formed accidentally from cerussa during the burning of the Pyræus. The colour was purple. It was imitated at Rome by burning silis marmarosus, which was probably a variety of some of our ochres.

      8. Besides the metals above enumerated, the ancients were also acquainted with quicksilver. Nothing is known about the first discovery of this metal; though it obviously precedes the commencement of history. I am not aware that the term occurs in the writings of Moses. We have therefore no evidence that it was known to the Egyptians at that early period; nor do I find any allusion to it in the works of Herodotus. But this is not surprising, as that author confines himself chiefly to subjects connected with history. Dioscorides and Pliny both mention it as common in their time. Dioscorides gives a method of obtaining it by sublimation from cinnabar. It is remarkable, because it constitutes the first example of a process which ultimately led to distillation.60

      Cinnabar is also described by Theophrastus. The term minium was applied to it also, till in consequence of the adulteration of cinnabar with red lead, the term minium came at last to be restricted to that preparation of lead. Theophrastus describes an artificial cinnabar, which came from the country above Ephesus. It was a shining red-coloured sand, which was collected and reduced to a fine powder by pounding it in vessels of stone. We do not know what it was. The native cinnabar was found in Spain, and was used chiefly as a paint. Dioscorides employs minium as the name for what we at present call cinnabar, or bisulphuret of mercury. His cinnabar was a red paint from Africa, produced in such small quantity that painters could scarcely procure enough of it to answer their purposes.

      Mercury is described by Pliny as existing native in the mines of Spain, and Dioscorides gives the process for extracting it from cinnabar. It was employed in gilding precisely as it is by the moderns. Pliny was aware of its great specific gravity, and of the readiness with which it dissolves gold. The amalgam was squeezed through leather, which separated most of the quicksilver. When the solid amalgam remaining was heated, the mercury was driven off and pure gold remained.

      It is obvious from what Dioscorides says, that the properties of mercury were very imperfectly known to him. He says that it may be kept in vessels of glass, or of lead, or of tin, or of silver.61 Now it is well known that it dissolves lead, tin, and silver with so much rapidity, that vessels of these metals, were mercury put into them, would be speedily destroyed. Pliny’s account of quicksilver is rather obscure. It seems doubtful whether he was aware that native argentum vivum and the hydrargyrum extracted from cinnabar were the same.

      Cinnabar was occasionally used as an external medicine; but Pliny disapproves of it, assuring his readers that quicksilver and all its preparations are virulent poisons. No other mercurial preparations except cinnabar and the amalgam of mercury seem to have been known to the ancients.62

      9. The ancients were unacquainted with the metal to which we at present give the name of antimony; but several of the ores of that metal, and of the products of these ores were not altogether unknown to them. From the account of stimmi and stibium, by Dioscorides63 and Pliny,64 there can be little doubt that these names were applied to the mineral now called sulphuret of antimony or crude antimony. It is found most commonly, Pliny says, among the ores of silver, and consists of two kinds, the male and the female; the latter of which is most valued.

      This pigment was known at a very early period, and employed by the Asiatic ladies in painting their eyelashes, or rather the insides of their eyelashes, black. Thus it is said of Jezebel, that when Jehu came to Jezreel she painted her face. The original is, she put her eyes in sulphuret of antimony.65 A similar expression occurs in Ezekiel, “For whom thou didst wash thyself, paintedst thy eyes”—literally, put thy eyes in sulphuret of antimony.66 This custom of painting the eyes black with antimony was transferred from Asia to Greece, and while the Moors occupied Spain it was employed by the Spanish ladies also. It is curious that the term alcohol, at present confined to spirit of wine, was originally applied to the powder of sulphuret of antimony.67 The ancients were in the habit of roasting sulphuret of antimony, and thus converting it into an impure oxide. This preparation was also called stimmi and stibium. It was employed in medicine as an external application, and was conceived to act chiefly as an astringent; Dioscorides describes the method of preparing it. We see, from Pliny’s account of stibium, that he did not distinguish between sulphuret of antimony and oxide of antimony.68

      9. Some of the compounds of arsenic were also known to the ancients; though they were neither acquainted with this substance in the metallic state, nor with its oxide; the nature of which is so violent that had it been known to them it could not have been omitted by Dioscorides and Pliny.

      The word σανδαραχη (sandarache) occurs in Aristotle, and the term αρῥενιχον (arrhenichon) in Theophrastus.69 Dioscorides uses likewise the same name with Aristotle. It was applied to a scarlet-coloured mineral, which occurs native, and is now known by the name of realgar. It is a compound of arsenic and sulphur. It was employed in medicine both externally and internally, and is recommended СКАЧАТЬ