Part 40

Under the above title almost the entire history of chemistry might be easily comprehended. The gradual growth of definite meanings attached to these terms has been coincident with the attainment of accurate notions concerning the composition of bodies. To the ancient philosophers sour wine, acetum vinæ, or acetum as it is still called, was the only acid definitely known. When the alchemists became busy trying to extract the virtue out of all substances they produced several acids by distillation. These they called, for example, spirit of vitriol, spirit of nitre, spirit of salt, meaning our sulphuric, nitric, and hydrochloric acids respectively. They regarded everything obtained by distillation as a spirit. When the theorists came forward, Becher, Stahl, and their followers, they treated these acids as original constituents of the substances from which they were obtained. Thus, when sulphur was burned phlogiston was set free, and acid remained. Lavoisier believed that the acidifying principle had been discovered in oxygen, and it was on this theory that he gave that element its name. But this idea broke down when Davy proved that there was no oxygen in the so-called muriatic, or oxy-muriatic acid. It was the subsequent recognition of the law of substitution which made it clear that the acids are, in fact, salts of hydrogen or of some metal substituted for the hydrogen.

The history of alkalies is as varied as is that of acids. The distinction between caustic alkalies and mild alkalies was a problem as far back as Dioscorides. By burning limestone caustic lime is produced. It was not an unreasonable presumption that the fire had created this causticity, and this theory was held with regard to all the alkalies until it was proved by Joseph Black, in 1756, that the caustic alkali was the result of a gas, fixed air, he named it, being driven off from the mild alkali.

The ancient Jews prepared what they called Borith (translated “soap” in Jeremiah, ii, 22, and Malachi, iii, 2) by filtering water through vegetable ashes. Borith was therefore an impure carbonate of potash. It is probable that the salt-wort was generally employed for this purpose, and some of the old versions of the Old Testament give the herb “Borith” as the proper sense of the passages referred to above. In any case the alkaline solution produced from vegetable ashes was used for bleaching and cleansing purposes. The Roman “lixivium” was similarly prepared, and the process is still followed in some countries where there are dense forests. The Arabic word “al-kali” was apparently applied to the product from the word “qaly,” which meant “to roast.” The earliest known use of the term is, however, found in the works of Albertus Magnus, early in the thirteenth century. A process of making caustic potash by filtering water through vegetable ashes with quicklime is described in the works attributed to Geber, but this is in a treatise now known to have been written in the thirteenth or fourteenth century. It was only in 1736 that the three alkalies, soda, potash, and ammonia, were definitely distinguished by Duhamel as mineral, vegetable, and animal or volatile alkalies.

A formula for a solution of caustic potash was given in the P.L., 1746, under the title of Lixivium Saponarium. Equal parts of Russian potashes and quicklime were mixed, wetted until the lime was slaked, water afterwards added freely, and after agitation the solution poured off. This was ten years before Black’s classic investigation already referred to. Before Black, and for some time afterwards, there were several theories in explanation of the action of the lime on the potashes. The lime had been tamed, but the potash had become more virulent. One popular suggestion was that the lime had withdrawn a kind of mucilage from the potashes; another that it had the effect of developing the power of the potashes by a mechanical process of comminution. A German chemist named Meyer, who vigorously opposed Black’s conclusions, maintained that the lime contained a certain Acidum Causticum or Acidum Pingue, which potashes extracted from it.

In the P.L., 1788, the process was altered by increasing the proportion of the lime, and the product was described as Aqua Kali Puri. Subsequently the proportion of the lime employed was reduced.

The word “salt” is traced back to the Greek “hals,” the sea, from which was formed the adjective “salos,” fluctuating (like the waves), and subsequently the Latin “sal.” Marine salt was therefore the original salt, and salts in chemistry were substances more or less resembling sea-salt. Generally, the term was limited to solids which had a taste and were soluble in water, but the notion was developed that salt was a constituent of everything, and this salt was extracted, and was liable to get a new name each time. Salt of wormwood, for instance, is one of the names which has survived as a synonym for salt of tartar, or carbonate of potash. Paracelsus insisted that all the metals were composed of salt, sulphur, and mercury, but these substances were idealised in his jargon and corresponded with the body, soul, and spirit, respectively.

Lavoisier was the first chemist who sought to define salts scientifically. He regarded them as a combination of an acid with a basic oxide. But when the true nature of chlorine was discovered it was found that this definition would exclude salt itself. This led to the adoption of the terms “haloid” and “amphide” salts, the former being compounds of two elements (now the combination of chlorine, bromine, iodine, cyanogen, or fluorine with a metal), and the latter being compounds of two oxides. The names were invented by Berzelius. Since then salts have been the subjects of various modern theories, electric and other, but they are always substances in which hydrogen or a metal substituted for it is combined with a radical. In a wide sense the acids are also salts.

ALCOHOL.

Al-koh’l was an Arabic word indicating the sulphide of antimony so generally used by Eastern women to darken their eyebrows, eyelashes, and the eyes themselves. Similar words are found in other ancient languages. Cohal in Chaldee is related to the Hebrew kakhal used in Ezekiel, xxiii, 40, in the sense of to paint or stain. The primary meaning of alcohol therefore is a stain. Being used especially in reference to the finely levigated sulphide of antimony, the meaning was gradually extended to other impalpable powders, and in alchemical writings the alcohol of Mars, a reduced iron, the alcohol of sulphur, flowers of brimstone, and similar expressions are common. As late as 1773 Baumé, in his “Chymie Experimentale,” gives “powders of the finest tenuity” as the first definition, and “spirit of wine rectified to the utmost degree” as the second explanation of the term alcohol. As certain of the finest powders were obtained by sublimation the transfer of the word to a fluid produced by a similar method is intelligible, and thus came the alcohol of wine, which has supplanted all the other alcohols.

Distillation is a very ancient process. Evidence exists of its use by the Chinese in the most remote period of their history, and possibly they distilled wine. But so far as can be traced spirit was not produced from wine previous to the thirteenth century. Berthelot investigated some alleged early references to it and came to the conclusion indicated. Aristotle alludes to the possibility of rendering sea water potable by vaporising it, and he also notes elsewhere that wine gives off an exhalation which emits a flame. Theophrastus mentions that wine poured on a fire as in libations can produce a flame. Pliny indicates a particular locality which produced a wine of Falerno, which was the only wine that could be inflamed by contact with fire. At Alexandria, in the first century of the Christian era, condensing apparatus was invented, and descriptions of the apparatus used are known, but no allusion to the distillation of wine occurs in any existing reference to the chemistry of that period. Rhazes, who died in A.D. 925, is alleged to have mentioned a spirit distilled from wine, but Berthelot shows that this is a misunderstanding of a passage relating to false or artificial wines.

Water distilled from roses is mentioned by Nicander, about 140 B.C., and the same author employs the term ambix for the pot or apparatus from which this water was obtained. The Arabs adopted this word, and prefixing to it their article, al, made it into alembic. This in English appeared for some centuries in the abbreviated form of limbeck. The Greek ambix was a cup-shaped vessel which was set on or in a fire, as a crucible was used.

Pissaeleum was a peculiar form of distillation practised by the Romans. It was an oil of pitch made by hanging a fleece of wool over a vessel in which pitch was being boiled. The vapour which collected was pressed out and used.

Distilled waters from roses and aromatic herbs figured prominently in the pharmacy of the Arabs, and Geber, perhaps in the eighth century, describes the process, and may have used it for other than pharmaceutical purposes. Avicenna likens the body of man to a still, the stomach being the kettle, the head the cap, and the nostrils the cooling tube from which the distillate drips.

M. Berthelot gives the following from the Book of Fires of Marcus Grecas, which he says could not be earlier than 1300, as the first definite indication of a method of producing what was called aqua ardens. “Take a black wine, thick and old. To ¼ lb. of this add 2 scruples of sulphur vivum in very fine powder, and 2 scruples of common salt in coarse fragments, and 1 or 2 lbs. of tartar extracted from a good white wine. Place all in a copper alembic and distil off the aqua ardens.” The addition of the salt and sulphur, M. Berthelot explains, was to counteract the supposed humidity.

Albucasis, a Spanish Arab of the eleventh century, is supposed from some obscure expressions in his writings to have known how to make a spirit from wine; but Arnold of Villa Nova, who wrote in the latter part of the thirteenth century, is the first explicitly to refer to it. He does not intimate that he had discovered it himself, but he appears to treat it as something comparatively new. Aqua vini is what he calls it, but some name it, he says, aqua vitæ, or water which preserves itself always, and golden water. It is well called water of life, he says, because it strengthens the body and prolongs life. He distilled herbs with it such as rosemary and sage, and highly commended the medicinal virtue of these tinctures.

It is worth remarking that when Henry II invaded and conquered Ireland in the twelfth century the inhabitants were making and drinking a product which they termed uisge-beatha, now abbreviated into whisky, the exact meaning of the name being water of life.

Raymond Lully, who acquired much of his chemical lore from Arnold of Villa Nova, was even more enthusiastic in praise of the aqua vitæ than his teacher. “The taste of it exceedeth all other tastes, and the smell all other smells,” he wrote. Elsewhere he describes it as “of marveylous use and commoditie a little before the joyning of battle to styre and encourage the soldiers’ minds.” He believed it to be the panacea so long sought, and regarded its discovery as evidence that the end of the world was near. The process for making the aqua vitæ as described by Lully was to digest limpid and well-flavoured red or white wine for twenty days in a closed vessel in fermenting horse-dung. It was then to be distilled drop by drop from a gentle fire in a sand-bath.

The chemical constitution of alcohol was speculated upon rather wildly by the chemists who experimented on it before Lavoisier. It was held to be a combination of phlogiston with water, but the phlogiston-philosophers disagreed on the question whether it contained an oil. Stahl, however, later supported by Macquer, found that an oil was actually separated from it if mixed with water and allowed to evaporate slowly in the open air, after treating it with an acid. Lavoisier, in 1781, carefully analysed spirit of wine and found that 1 lb. yielded 4 oz. 4 drms. 37½ grains of carbon, 1 oz. 2 drms. 5½ grains of inflammable gas (hydrogen), and 10 oz. 1 drm. 29 grains of water. It was de Saussure who later, following Lavoisier’s methods of investigation, but with an absolute alcohol which had been recently produced by Lowitz, a Russian chemist, showed that oxygen was a constituent of alcohol. Berthelot succeeded in making alcohol synthetically in 1854. His process was to shake olefiant gas (C{2}H{4}) vigorously with sulphuric acid, dilute the mixture with eight to ten parts of water, and distil. Meldola, however (“The Chemical Synthesis of Vital Products,” 1904), insists that an English chemist, Henry Hennell, anticipated Berthelot in this discovery.

ALUM.

Alum is a substance which considerably mystified the ancient chemists, who knew the salt but did not understand its composition. Ancient writers like Pliny and Dioscorides were acquainted with a product which the former called alumen and which is evidently the same as had been described by Dioscorides under the name of Stypteria. Pliny says there were several varieties of this mineral used in dyeing, and it is clear from his account that his alumen was sometimes sulphate of iron and sometimes a mixture of sulphate of iron with an aluminous earth. It is the fact that where the various vitriols are found they are generally associated with aluminous earth.

Alum as we know it was first prepared in the East and used for dyeing purposes. Alum works were in existence some time subsequent to the twelfth century at a place named Rocca in Syria, which may have been a town of that name on the Euphrates, or more probably was Edessa, which was originally known as Roccha. It has been supposed that it was the manufacture of alum at this place which bequeathed to us the name of Rock or Rocha alum, but the Historical English Dictionary says this derivation is “evidently unfounded.”

The alchemists were familiar with alum and knew it to be a combination of sulphuric acid with an unknown earth. Van Helmont was the first to employ alum as a styptic in uterine hæmorrhage, and Helvetius made a great reputation for a styptic he recommended for similar cases. His pills were composed of alum 10 parts, dragon’s blood 3 parts, honey of roses q.s., made into 4 grain pills, of which six were to be taken daily. Alum and nutmeg equal parts were given in agues. Paris says the addition of nutmeg to alum corrects its tendency to disturb the bowels. It has also been advocated in cancer and typhoid, but these internal uses have been generally abandoned. Spirit of Alum is occasionally met with in alchemical writings. It was water charged with sulphuric acid obtained by the distillation of alum over a naked fire.

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.