It is not very probable that Dioscorides, Pliny, and others who lived nearly about the same time, were acquainted with sal-ammoniac, or mentioned it in their works; for no part of mineralogy was then so defective as that which is the most important, and which treats of salts. The art of lixiviating earths and causing saline solutions to crystallize was then so little known, that, instead of green vitriol, vitriolic minerals, however impure, were employed in making ink, dye-liquors, and other things. Places for boiling vitriol were not then established, and therefore Pliny beheld with wonder blue vitriol, which in his time was made only in Spain, as a thing singular in its kind, or which had not its like. On this account those salts only were known which occur in a native state, or which crystallize as it were of themselves, without any artificial preparation, as is the case with bay salt. But that neutral salt, formed of muriatic acid and ammonia, occurs very seldom in a native state, and almost exclusively among the productions of volcanoes. I do not, however, suppose that this volcanic sal-ammoniac was the first known, but that it was first considered to be sal-ammoniac after that salt had been long obtained by another method, and long used.

But even if it should be believed that our sal-ammoniac was known to the ancients, how are we to discover it with certainty in their writings? This salt has little or nothing by which these writers could characterize it. Neither its external form nor taste is so striking that it could be described by them with sufficient precision. The use of it also could not at that time be so important and necessary, as to enable us to determine whether they were acquainted with it; whereas, on the other hand, green vitriol and alum can easily be distinguished among the materials for dyeing.

Nay, if this salt had been then made, as it is made at present in Egypt, and if any allusion to it were found, one might readily conjecture that sal-ammoniac were really meant. But even though it must be admitted that traces of sublimation being employed occur in the writings of Dioscorides and others, who lived nearly at the same period, we are not authorized to suppose that the knowledge of it was sufficient for the preparation of this salt.

Besides, there are two properties with which the ancients might have accidentally become acquainted, and which in that case would have been sufficient to make known or define to us this salt. In the first place, by an accidental mixture of quicklime, the strong smell or unsupportable vapour diffused by the volatile alkali separated from the acid might have been observed. In the second place, it is very possible that the complete volatilization of this salt on burning coals may have been remarked; for it had been long known that common salt decrepitates in the fire. This excited wonder, and in examining other salts people were accustomed to observe whether they possessed that property also. Had any one, with this view, thrown a bit of sal-ammoniac on a burning coal, he must have seen with astonishment that instead of decrepitating it became entirely volatilized. For this experiment, however, very pure sal-ammoniac would have been necessary. Had a little common salt been mixed with it, decrepitation would not have been altogether prevented; and if the sal-ammoniac had been rendered impure by earthy particles, as is almost always the case with the volcanic, some earth at least would have remained behind on the coals.

The name sal-ammoniacus is indeed old; but as those who, in consequence of the name, considered the alumen of the ancients to be our alum, and their nitrum to be our saltpetre, were in an error, we should be equally so were we to consider their sal-ammoniac to be the same as ours. Our forefathers believed that the ancient writers were acquainted with all minerals, as well as with all plants; and when they discovered a new one, they searched in old books till they found a name which would suit it, or which at any rate had not been given to another. Our sal-ammoniac, in all probability, acquired in the same manner its name, which is not often to be found in the writings of the ancients972.

When everything they have said of it is collected and impartially examined, no proofs will be found that under that name they understood our sal-ammoniac. On the contrary, one will soon be convinced that sal-ammoniacus was nothing else than impure marine salt. As the ancients were not acquainted with the art of separating salts, of refining and crystallising them, they gave to each variety or kind in the least different, which was distinguished either by the intermixture of some foreign substance or by an accidental formation, a particular name; and, considering the wants of that period, this method was not so bad. For among the impure saline substances, there were always some which were found to be fitter than others for certain purposes. On this account they distinguished with so much care misy, sory, chalcitis and melanteria, instead of which we use a substance contained in all these minerals, that is to say, green vitriol. Our apothecary shops however have at present the lixivious salt under the name of various plants, from which it is extracted, with different degrees of purity.

When this is known, it will excite no wonder that the sal-ammoniacus of the ancients was nothing else than our common salt. Dioscorides and Pliny speak of it expressly as a kind of this salt; and Columella973, in a prescription for an eye-salve, recommends rock-salt, either Spanish, Ammoniacal, or Cappadocian. Pliny says974 that sal-ammoniacus was found in the dry sandy deserts of Africa, as far as the oracle of Ammon. It is stated, both by him and Dioscorides975, that this salt can be split or broken into smooth pieces; and the former adds, that the best are white and transparent; that it however has an unpleasant taste, but can be used in medicine. In like manner later physicians, when they wish to prescribe common salt, recommend in particular the ammoniac. Thus Aetius, who lived in the fifth century, remarks, that when fossil, or as we say at present native salt, is employed, ammoniac or Cappadocian ought to be chosen.

From what is said by Pliny, it may with certainty be concluded that this salt was dug up from pits or mines in Africa; for he relates, that it appeared wonderful that a piece of it, which in the pit was very light, became, on exposure to the open air, much heavier. Without repeating the explanation which he gives of this phÆnomenon, I shall only remark, that many kinds of rock-salt, taken from the mines of Wieliczka, experience the same change in the air; so that blocks which a labourer can easily carry in the mine, can scarcely be lifted by him after they have been some time exposed to the air. The cause here is undoubtedly the same as that which makes many kinds of artificial salt to become moist and to acquire more weight. In this case it is owing to some impurity, such as muriate of lime, which is called sal-ammoniacus fixus976, and which attracts from the atmosphere so much moisture, that it deliquesces in it to the so-called oil of lime.

Synesius, who was born in Egypt in the fifth century, in the Pentapolitan town Cyrene, and who resided as bishop in Ptolemais, the capital of the district, says, in a letter wherein he describes many rarities of his native country, that what was called sal-ammoniacus977, both according to its appearance and taste, was a salt of a good quality, fit for use; that it lay under a soft kind of stone which covered it like a crust, and that it could be easily dug up when this stone was removed.

Herodotus, Strabo, Arrian, and others, speak of rock-salt which was dug up in Ammonia, and carried thence as an article of merchandise. The first mentions a hill of salt; and we are told by the last, that native salt was brought to Egypt as a present to the king and others, from the neighbourhood of the oracle of Ammon, by the priests of that place, in boxes made of palms worked together. Many pieces were three inches in length; and because this substance was purer than bay salt, and as clear as crystal, it was particularly employed in sacrifices. This salt is certainly that which, under the name of sal-ammoniacus, was sent from Egypt to the king of Persia, like the water of the Nile, as is related by AthenÆus from an historian long since lost978.

It is also certain that the old Arabian physicians, Avicenna and Serapion, who both lived in the eleventh century, under the name sal-ammoniacus understood nothing else than rock-salt. The former says that it ought to split easily, and to be clear and transparent like crystal; and the latter states that this salt is cut from the solid rock, and that it is sometimes clear as crystal, sometimes reddish, sometimes blackish, sometimes of another colour, sometimes hard, and sometimes friable, or, as the translator expresses it, pulverulent. All these colours and properties are not uncommon in rock-salt, and always proceed, no doubt, from an admixture of ferruginous earth. Serapion says that this salt was obtained from Corasini. I shall leave it to others to determine where this country was situated. He often names it, and says that mala granata and bezaar were obtained from it. But who knows how the name was written in the original? And the Arabian author perhaps did not mention the place where the salt was dug up, but that from which, in his time, it was procured979.

In regard to the purpose to which the ancients applied their sal-ammoniacus, it appears that it required only common salt and not sal-ammoniac. It is oftenest mentioned by the physicians, because it was the purest table salt that could then be procured. On that account it has been praised by Scribonius Largus, who lived in the first century, and by Aetius who lived in the fifth, as well as by Avicenna, Serapion, and others. I have however not yet met with it in the writings of Hippocrates or Galen. In the works of the Greek agriculturists it occurs in a recipe for the preparation of a cement employed to close up wine vessels980. According to a recipe of Apicius, in his book on cookery, sal-ammoniacus was to be roasted. By these means this rock-salt lost its water of crystallization and became stronger. On this account, in Transylvania, Siberia, and other countries, before it is brought to the table it is pounded and roasted. Of our sal-ammoniac, however, were it roasted, very little would remain. But whether the ammonium which Palladius recommends for a cement981 be that salt, I will not pretend to determine. On the other hand, I have no hesitation to contradict the old commentator on Ovid, who, in a passage where the poet recommends sal-ammoniacus in making a cosmetic water, understands the resin or gum of that name. Ovid however had no intention that young women should lacker themselves.

For the reasons therefore already mentioned, I am convinced that the sal-ammoniacus of the ancients was rock-salt, and not our sal-ammoniac. The oldest commentators also on these writers had no idea of any other than rock-salt; and it was not till a later period, when our sal-ammoniac was introduced into commerce, and acquired that name, that the most learned commentators began expressly to remark, that the new sal-ammoniac, notwithstanding its appellation, was different from the sal-ammoniacus of the ancients. As this could not then be obtained, people used the former, which they considered only as an artificial substitute for the latter, though it was incapable of supplying its place. But in more modern times, when our sal-ammoniac became common, and physicians and mineralogists no longer took the trouble to read the works of the ancients, some of them, if not the greater part, spoke in such a manner as if our sal-ammoniac had been the sal-ammoniacus of the ancients; and it was then generally believed that it had been, at any rate, known and used since the time of Dioscorides and Pliny.

No one has maintained this with greater confidence and zeal than F.I.W. SchrÖder982, whose judgement however was perverted by alchemistic conceits. According to his assertion, the Egyptians practised from the earliest periods the art of making sal-ammoniac, but they kept it a secret; and he obscurely hints at the purpose for which these great chemists used so much salt. He refers, on this occasion, to what Pliny says of flos salis983, in which he thinks he can find the martial sal-ammoniac984 flowers of our chemists, or the so-called flores salis ammoniaci martiales. Those who cannot make this discovery he declares to be ignorant and blind. This decision, however, when the character of the person who gives it is considered, cannot dissipate a single doubt. It is certain that what Dioscorides and Pliny call flos salis has never yet been defined. It was moist, oily, and saline; and in the vessels, in which it was sent from Egypt, was grey at the top, saffron-coloured at the bottom, and emitted a bad smell. The most ingenious conjecture was that of Cordus985, who thought that it might be sperma ceti; but though I should prefer this opinion to that of SchrÖder, I must confess that, on the grounds adduced by Matthioli and Conrad Gesner, it has too much against it to be admitted as truth.

The first distinct traces of our sal-ammoniac which I have yet met with are to be found in the works of the Arabians986. In a writing of Geber, there is a prescription how to purify sal-ammoniac by sublimation, and in another a receipt for making it; so that there can be no doubt that the author was acquainted with our salt. But this furnishes very little towards the history of it. The period when that celebrated chemist lived is uncertain. If, as Leo says987, he flourished a hundred years after Mahomet, that is to say in the eighth century, his works must have been interpolated with many additions, which criticism has not yet been able to separate. Many of them cannot be of great antiquity; and the uncertainty is increased by some of the editions differing from each other in important passages. Whole sections, which some have, are wanting in others; and the titles and order of the books and sections are different almost in each. When the same circumstances are found in several editions, it is observed that they essentially differ. What, therefore, is now found in the writings of Geber, as they are called, was certainly not all known in the eighth century.

The same uncertainty prevails in regard to the chemical works of Avicenna, who lived in the beginning of the eleventh century, and who certainly treats of sal-ammoniac. But when these are compared with the medical works of this author, which are subject to no doubt, it is evidently perceived that the former must have been the production of a very different and much younger writer. In the works of the physician Avicenna, sal-ammoniacus means always rock-salt. It is worthy of remark, that Avicenna the chemist says, that sal-ammoniac comes from Egypt, India, and Forperia.

We know with more certainty that Albucasis, or Bulcasis, was acquainted with sal-ammoniac, as well as the method of preparing it, which he describes, and also the preparation of medicines in general, in his book often printed under the title of Liber servitoris988. However unintelligible the translation often is, one can easily discover in what manner sublimation was formerly performed in earthen vessels. But the period when this Arabian writer lived is doubtful, though it is generally admitted that he died in the year 1122.

But whence did Europe obtain this salt, in the twelfth and succeeding centuries? When and in what manner was the preparation of it found out in Egypt? For what purpose was it first used by our ancestors? I have not yet met with any information to enable me to answer these questions, though it is probable that it might be found in old books of travels, and particularly in the works of Arabian writers. In the valuable but not altogether intelligible book of Pegolotti989, from which I have learned many things respecting the trade of the fourteenth and fifteenth centuries, nothing is said in regard to the place where it was obtained, but that it was procured in white, hard, and opake cakes. It is mentioned in the custom-house tariff of Pisa for the year 1408.

Biringoccio, who lived in the end of the fifteenth and beginning of the following century990, knew nothing more than that, according to report, it came from Cyrene or Armenia. CÆsalpin, his contemporary, gave, for the preparation of it, a prescription which is undoubtedly borrowed from the Arabians. This author says, very properly, that it is obtained in white transparent cakes, blackish on the outside; but adds, erroneously, that it comes from Germany, though the same thing has been repeated by Brasavolus and Matthioli. Porta says, with more truth, that it comes from the East. He asserts also, that he was the first person who found real sal-ammoniac on volcanic mountains, and he wishes that his discovery might be confirmed by skilful naturalists991. This may serve as an additional proof, were such necessary, in opposition to those who think that the first real sal-ammoniac introduced into commerce was the volcanic. Imperato considers Porta’s observation as generally acknowledged, but without naming him. The former has described, in a fuller and more correct manner than any of his predecessors, the properties of sal-ammoniac992; and he states, as does also Agricola993, that it is entirely dissipated in the fire. He adds, that it promotes the production of a celestial blue colour, and in all probability he here alludes to a solution of copper.

Without attempting to examine at what time the art was discovered of converting the nitric acid into aqua regia by the addition of sal-ammoniac, I shall only remark that, at any rate, it was known in the sixteenth century; for Imperato says that sal-ammoniac is employed in the solution of gold; and Biringoccio994, who is older, recommends nitrous acid prepared with sal-ammoniac for dissolving metals, and particularly gold. I will not either determine how old the use of this salt is in soldering and tinning; but I must observe, that it was known to Agricola995 and Imperato. I however doubt whether it was very common, because Biringoccio996 recommends borax for that purpose, without so much as mentioning sal-ammoniac; though it is possible that I may have overlooked it.

We are now arrived at the modern history, which I shall give in as brief a manner as I can, because it has been already fully treated on by others. What was long ago shown by the celebrated Mr. Boyle was proved in the year 1716 by Geoffroy the younger, that sal-ammoniac was composed of the muriatic acid and volatile alkali, and that it could be thence prepared in Europe by sublimation997. In the same year the jesuit Sicard gave the first certain account of the sal-ammoniac manufactories at Damayer, in the Delta, and described in what manner this salt was prepared there, by sublimation in glass vessels, from the soot of the burnt dung of camels and cows, which is used in Egypt for fuel, with the addition of sea salt and urine998. In the year 1719, the Academy of Sciences at Paris received from Lemere, the French consul at Cairo, an account of the process employed; but it contained no mention either of sea salt or of urine999. Afterwards this information was in part confirmed, and in part rectified and enlarged, by Paul Lucas1000, Granger, or, as he was properly called, Tourtechot1001, and the celebrated travellers Shaw, Pocock, Norden, Hasselquist, Niebuhr, and Mariti.

Several writers have asserted that sal-ammoniac comes also from the East Indies. It is mentioned by Tavernier among the wares which in his time were brought from Amadabat, in the territories of the Mogul, to Surat; and Geoffroy states, that when the trade of Marseilles was interrupted by the plague, the French obtained from Holland sal-ammoniac, which was shaped like a truncated cone, and was given out to be Indian1002. Pomet also says, that some of the same kind was formerly procured from Venice and Holland. But Gaubius asserts that he was never able to hear of any such sal-ammoniac in Holland1003; nor is it to be found in the price currents of the East India Company. I am almost inclined to suspect that these truncated cones were formed by the merchants from broken pieces or fragments of the Egyptian sal-ammoniac, by solution and imperfect crystallization or sublimation. In this manner the merchants at Marseilles convert the refuse of the Egyptian sal-ammoniac into cakes by a new sublimation, in order that it may become more saleable, though it is not readily purchased by artists. Gaubius, however, has described a kind of sal-ammoniac which he obtained from India, with the information that it was made in Hindostan from the soot of animal dung; but in my opinion this requires further confirmation1004.

Where and at what time the first works for making sal-ammoniac were established in Europe, I am not able to determine. The account given by Thurneisser, that the first sal-ammoniac was made in the Tyrol in the ninth century, is truly ridiculous. It is not worth the trouble to inquire where he or Paracelsus found this foolish assertion. One might be almost induced to believe, that in the time of Boyle there were manufactories of sal-ammoniac in Europe1005. But perhaps there may be no other foundation for all this than the before-mentioned assertion of CÆsalpinus, that this salt came from Germany. At Bamberg, the Germans were long accustomed to boil the sediment of the salt-pans with old urine, and to sell it cheap for sal-ammoniac; and Weber asserts that some of the same kind is still made at Vienna. The hundred weight costs from twenty to thirty florins, but the refuse may be purchased for a mere trifle. If I am not mistaken, the first real manufactories of sal-ammoniac were established in Scotland; and the oldest of these, perhaps, was that erected by Dovin and Hutton at Edinburgh in 1756, and which, like many in England, manufactures this salt on a large scale1006. Among the later undertakings of this kind is Gravenhorst’s manufactory at Brunswick, and that which in the neighbourhood of Gothenburg manufactures sal-ammoniac from the refuse left in making train oil.

[Sal-ammoniac is now prepared either by the destructive distillation of bones or coal. The gas-liquor supplies, we believe, the largest part. This fluid contains hydrosulphuret and carbonate with some other salts of ammonia. It is decomposed with sulphuric acid, and on evaporation the sulphate of ammonia is obtained in a crystalline state. This is then mixed with common salt and the mixture heated in iron vessels, whereupon the muriate of ammonia sublimes.

Sal-ammoniac is exported in considerable quantities to Russia and other parts of the continent and to the United States.]