Until the fifteenth century the only alum factories from which Europe was supplied were at Constantinople, Smyrna, and Trebizonde. Beckman relates that an alum factory was founded in the Isle of Ischia, on the coast of Tuscany, by a Genoese merchant named Bartholomew Perdix, who had learnt the art at Rocca. Very soon afterwards John de Castro, a Paduan who had been engaged in cloth dyeing at Constantinople but had lost all his property when that city was captured by Mahomet II in 1453, was appointed to an office in the Treasury of the Apostolic Chamber, and in the course of his duties found what he believed to be an aluminous rock at Tolfa, near Civita Vecchia. He asked the Pope, Pius II, to allow him to experiment, but it was some years before the necessary permission was granted. When at last the truth of Castro’s surmise was established the Pope was greatly interested. He looked upon the discovery as a great Christian victory over the Turks, and handsomely rewarded de Castro, to whom, besides, a monument was erected in Padua inscribed “Joanni de Castro, Aluminis inventor.” The factory brought in a splendid revenue to the Apostolic exchequer, and the Pope did his utmost to retain the monopoly, for when in consequence of the extravagant prices to which the Tolfa alum was raised merchants began again to buy the Eastern product his Holiness issued a decree prohibiting Christians from purchasing from the infidels under pain of excommunication. Later, when, in Charles I’s reign, Sir Thomas Challoner discovered an aluminous deposit near his home at Guisborough in Yorkshire, and persuaded some of the Pope’s workmen to come there to work the schist, he and those whom he had tempted away were solemnly and most vigorously “cursed.”
Meanwhile the nature of the earth with which the sulphuric acid was combined remained unknown to chemists. Stahl worked at the problem and came to the conclusion that it was lime. The younger Geoffroy, a famous pharmacist of Paris, ascertained (1728) that the earth of alum was identical with that of argillaceous earth and Alumina was for some time called Argile. Marggraf observed that he could not get alum crystals from a combination of argile and sulphuric acid, but noting that in the old factories it had been the custom to add putrid urine to the solution, for which carbonate of potash was subsequently substituted, went so far as to make the salt, but did not appreciate that it was actually a double salt. The name alumina which the earth now bears was given to it by Morveau. It was Vauquelin (another pharmacist) who clearly proved the composition of alum, and Lavoisier first suggested that alumina was the oxide of a metal. Sir Humphry Davy agreed with this view but failed to isolate the metal. Oersted was the first to actually extract aluminium from the oxide, but his process was an impracticable one, but in 1828 Woehler, and in 1858 Deville, found means of producing the metal in sufficient abundance to make it a valuable article of industry.
Ammonia.
The chemical history of ammonia commences in Egypt with Sal Ammoniac. This is mentioned by Pliny under the name of Hammoniacus sal. Dioscorides also alludes to it; but in neither case does the description given fit in satisfactorily with the product known to us. Dioscorides, for instance, states that sal ammoniac is particularly prized if it can lie easily split up into rectangular fragments. It has been conjectured that what was called sal ammoniac by the ancient writers was, at least sometimes, rock salt.
The name is generally supposed to have been derived from that of the Egyptian deity, Amn or Amen, or Ammon as the Greeks called him, and in the belief that he was the same god as Jupiter he is referred to in classical literature as Zeus-Ammon or Jupiter-Ammon. The principal temple of this god was situated in an oasis of the Libyan desert which was then known as Ammonia (now Siwah), and if, as is supposed, the salt was found or produced in that locality its name is thus accounted for. Gum ammoniacum was likewise so called in the belief that it was obtained in that district, though the gum with which we are familiar and which comes from India and Persia, is quite a different article from the African gum the name of which it has usurped. Pliny derives the name of the salt from the Greek “ammos,” sand, as it was found in the sand of the desert; an explanation which overlooks the fact that the stuff was called by a similar name in a country where the sand was not called ammos. In old Latin, French, and English writings “armoniac” is often met with. This was not inaccurate spelling; it was suggested by the opinion that the word was connected with Greek, armonia, a fastening or joining, from the use of sal ammoniac in soldering metals.
That Pliny did sometimes meet with the genuine sal ammoniac is conjectured by his allusion to the “vehement odour” arising when lime was mixed with natrum. Probably this natrum was sal ammoniac. Among the Arabs the term sal ammoniac often means rock salt; but in the writings attributed to Geber, some of which may be as late as the twelfth or thirteenth century, our sal ammoniac is distinctly described. It is also exactly described by Albertus Magnus in the thirteenth century, who mentions an artificial as well as a natural product, but does not indicate how the former was made. From this time sal ammoniac became a common and much-prized substance in alchemical investigations, as from it chlorides were obtained. The “volatile spirit of sal ammoniac” was made by distilling a solution of sal ammoniac with quicklime, and of course the same product was obtained in other ways, especially by distilling harts’ horns, and this was always regarded as having peculiarly valuable properties. A “sal ammoniacum fixum” was known to the alchemists of the fifteenth century. It was obtained as a residue after sal ammoniac and quicklime had been sublimed. It was simply chloride of calcium.
The so-called natural sal ammoniac was for centuries brought from Egypt, and was supposed to have been mined in the earth or sand of that country. In 1716 the younger Geoffroy came to the conclusion that it must be a product of sublimation, and he read a paper to the French Academy giving his reasons for this opinion. Homberg and Lemery opposed this view with so much bitterness, however, that the paper was not printed. In 1719 M. Lemaire, French Consul at Cairo, sent to the Academy an account of the method by which sal ammoniac was produced in Egypt, and this report definitely confirmed the opinion which Geoffroy had formed. It was, said M. Lemaire, simply a salt sublimed from soot. The fuel used in Egypt was exclusively the dung of camels and other animals which had been dried by the sun. It consisted largely of sal ammoniac, and this was retained in the soot. For a long time an artificial sal ammoniac had been manufactured at Venice, and a commoner sort also came from Holland. These were reputed to be made from human or animal urine. The manufacture of sal ammoniac was commenced in London early in the eighteenth century by a Mr. Goodwin.
A formula for Sal Ammoniacum Factitium in Quincy’s Dispensatory (1724) is as follows:—Take of Urine lb. x.; of Sea-salt lb. ii.; of Wood soot lb. i.; boil these together in a mass, then put them in a subliming pot with a proper head, and there will rise up what forms these cakes. Dr. James (1764) states that at Newcastle one gallon of the bittern or liquor which drains from common salt whilst making, was mixed with 3 gallons of urine. The mixture was set aside for 48 hours to effervesce and subside. Afterwards the clear liquor was drawn off and evaporated in leaden vessels to crystallisation. The crystals were sublimed. A sal ammoniacum volatile was made by subliming sal ammoniac and salt of tartar (or lime or chalk) together. Sometimes some spices were put into the retort. This salt was used for smelling-bottles. Aqua regia was made by distilling sal ammoniac and saltpetre together.
Sal Volatile Oleosum was introduced by Sylvius (de la Boe) about the year 1650. It became a medicated stimulant of the utmost popularity, and there were many formulas for it. One of the most famous was Goddard’s Drop. (See page 319).