I estimate that William Oake invented the mild curing system around 1830. He was a trained chemist in Ireland. I am interested to understand what the chemists knew in the 1830s about microorganisms, nitrate salts and meat curing. These are extracts from the work of Thomas Thomson on the subject from his publication, The History of Chemistry by Thomas Thomson published in 1830.
The Hangover of Alchemy and What was Known from Facts
Reading this work reassured me that by 1830, the thinking of Chemistry sufficiently shifted away from the influence of Alchemy. Alchemy was a philosophically based system of thinking focused on the creation of gold from other elements, and Thomson devotes Chapter one to this pursuit. From reading the work of Liebig and Hoffmann, I know that the aftermath of the impact of this philosophical approach to science lingered on till very late in the 1800s.
If I thought that the concept of sticking to facts and not trying to come up with some grand unified theory was the invention of Hofmann, I was wrong. I quote the refreshing opening paragraph of Thomson. He wrote, “. . . the ancients have left no chemical writings behind them, and (that) no evidence whatever exists to prove that the science of chemistry was known to them. Scientific chemistry, on the contrary, took its origin from the collection and comparison of the chemical facts, made known by the practice and improvement of those branches of manufactures which can only be conducted by chemical processes. Thus the smelting of ores, and the reduction of the metals which they contain, is a chemical process; because it requires, for its success, the separation of certain bodies which exist in the ore chemically combined with the metals; and it cannot be done, except by the application or mixture of a new substance, having an affinity for these substances, and capable, in consequence, of separating them from the metal, and thus reducing the metal to a state of purity. The manufacture of glass, of soap, of leather, are all chemical, because they consist of processes, by means of which bodies, having an affinity for each other, are made to unite in chemical combination. Now I shall in this chapter point out the principal chemical manufactures that were known to the ancients, 50that we may see how much they contributed towards laying the foundation of the science. The chief sources of our information on this subject are the writings of the Greeks and Romans. Unfortunately the arts and manufactures stood in a very different degree of estimation among the ancients from what they do among the moderns. Their artists and manufacturers were chiefly slaves.”
This is one of the reasons why the historical record of meat curing is almost completely absent from ancient writings. This view of its “inferiority” continued with serious scientists in the years to come, with almost no reference to it till food science and meat science, in particular, came into their own during the early 1900s. In the case of meat, though, it was not only the province of slaves but also of housewives.
Let’s continue reading Thomson’s quote. “The citizens of Greece and Rome devoted themselves to politics or war. Such of them as turned their attention to learning confined themselves to oratory, which was the most fashionable and the most important study, or to history, or poetry. The only scientific pursuits which ever engaged their attention, were politics, ethics, and mathematics. For, unless Archimedes is to be considered as an exception, scarcely any of the numerous branches of physics and mechanical philosophy, which constitute so great a portion of modern science, even attracted the attention of the ancients.”
“In consequence of the contemptible light in which all mechanical employments were viewed by the ancients, we look in vain in any of their writings for accurate details respecting the processes which they followed. The only exception to this general neglect and contempt for all the arts and trades, is Pliny the Elder, whose object, in his natural history, was to collect into one focus, every thing that was known at the period when he lived.” Pliny the Elder’s detailed description of the production of hams is consequently probably the most well-known account from antiquity on the subject.
Thomson continues about Pliny the Elder, that “his work displays prodigious reading, and a vast fund of erudition. It is to him that we are chiefly indebted for the knowledge of the chemical arts which were practised by the ancients. But the low estimation in which these arts were held, appears evident from the wonderful want of information which Pliny so frequently displays, and the erroneous statements which he has recorded respecting these processes. Still a great deal may be drawn from the information which has been collected and transmitted to us by this indefatigable natural historian.”
The first class of interest to us is starch. Thompson writes, “the manufacture of starch was known to the ancients. Pliny informs us that it was made from wheat and from siligo, which was probably a variety or sub-species of wheat. The invention of starch is ascribed by Pliny to the inhabitants of the island of Chio, where in his time the best starch was still made. Pliny’s description of the method employed by the ancients of 96making starch is tolerably exact. Next to the China starch that of Crete was most celebrated; and next to it was the Egyptian. The qualities of starch were judged of by the weight; the lightest being always reckoned the best.”
He discusses the production of beer, but the real relevance to later meat scientists came when he discusses MISCELLANEOUS OBSERVATIONS. Before we get to the particular relevance to our considerations of elements that would be important in mfoor processing and preserbation we pause for a moment to note his mention of gasses. The progress of Chemistry was effectively halted until such time as they could recognise the existence of gassess as distinct separate elements, governed by its own set of peculiar laws. His short mention of it shows that this realisation has been established by 1830
Thomson writes, “the ancients seem to have been ignorant of the nature and properties of air, and of all gaseous bodies. Pliny’s account of air consists of a single sentence: “Aër densatur nubibus; furit procellis.” “Air is condensed in clouds, it rages in storms.” Nor is his description of water much more complete, since it consists only of the following phrases: “Aquæ subeunt in imbres, rigescunt in grandines, tumescunt in fluctus, præcipitantur in torrentes.” “Water falls in showers, congeals in hail, swells in waves, and rushes down in torrents.” In the thirty-eighth chapter of the second book, indeed, he professes to treat of air; but the chapter contains merely an enumeration of meteorological phenomena, without once touching upon the nature and properties of air.”
“Pliny, with all the philosophers of antiquity, admitted the existence of the four elements, fire, air, water, and earth; but though he enumerates these in the fifth chapter of his first book, he never attempts to explain their nature or properties. Earth, among the ancients, had two meanings, namely, the planet on which we live, and the soil upon which vegetables grow. These two meanings still exist in common language. The meaning afterwards given to the term, earth, by the chemists, did not exist in the days of Pliny, or, at least, was unknown to him; a sufficient proof that chemistry, in his time, had made no progress as a science; for some notions respecting the properties and constituents of those supposed four elements must have constituted the very foundation of scientific chemistry.”
One of the elements that would become extremely important for the dissiplin of food science is the concept of acids and basis. Thomson writes, “the ancients were acquainted with none of the acids which at present constitute so numerous a tribe, except vinegar, or acetic acid; and even this acid was not known to them in a state of purity. They knew none of the saline bases, except lime, soda, and potash, and these very imperfectly. Of course the whole tribe of salts was unknown to them, except a very few, which they found ready formed in the earth, or which they succeeded in forming by the action of vinegar on lead and copper. Hence all that extensive and most important branch of chemistry, consisting of the combinations of the acids and bases, on which scientific chemistry mainly depends, must have been unknown to them.”
“Sulphur occurring native in large quantities, and being remarkable for its easy combustibility, and its disagreeable smell when burning, was known in the very earliest ages. Pliny describes four kinds of sulphur, differing from each other, probably, merely in their purity. These were1. Sulphur vivum, or apyron. It was dug out of the earth solid, and was doubtless pure, or nearly so. It alone was used in medicine.2. Gleba—used only by fullers.3. Egula—used also by fullers.Pliny says, it renders woollen stuffs white and soft. It is obvious from this, that the ancients knew the method of bleaching flannel by the fumes of sulphur, as practised by the moderns.4. The fourth kind was used only for sulphuring matches.
Sulphur, in Pliny’s time, was found native in the Æolian islands, and in Campania. It is curious that he never mentions Sicily, whence the great supply is drawn for modern manufacture.
In medicine, it seems to have been only used externally by the ancients. It was considered as excellent for removing eruptions. It was used also for fumigating.
Pliny’s term alumen was, or included, aluminium sulphate minerals. Another source states that “alum ( alumen , στυπτηρία ). Just as today the word A. is a collective name for a whole group of salts of sulfuric acid and not just a name for the double salt of sulphate of potash and sulphate of alumina, so the words alumen and στυπτηρία also appear among the ancientsto have been used in the same or a somewhat broader sense, whereby the individual varieties were distinguished more precisely partly by the place where they were found, partly by special additions to the name.” (Wikisource)
Thomson writes, “the word alumen, which we translate alum, occurs often in Pliny; and is the same substance which the Greeks distinguished by the name of στυπτηρια (stypteria). It is described pretty minutely by Dioscorides, and also by Pliny. It was obviously a natural production, dug out of the earth, and consequently quite different from our alum, with which the ancients were unacquainted. Dioscorides says that it was found abundantly in Egypt; that it was of various kinds, but that the slaty variety was the best. He mentions also many other localities. He says that, for medical purposes, the most valued of all the varieties of alumen were the slaty, the round, and the liquid. The slaty alumen is very white, has an exceedingly astringent taste, a strong smell, is free from stony concretions, and gradually cracks and emits long capillary crystals from these rifts; on which account it is sometimes called trichites. This description obviously applies to a kind of slate-clay, which probably contained pyrites mixed with it of the decomposing kind. The capillary crystals were probably similar to those crystals at present called hair-salt by mineralogists, which exude pretty abundantly from the shale of the coal-beds, when it has been long exposed to the air. Hair-salt differs very much in its nature. Klaproth ascertained by analysis, that the hair-salt from the quicksilver-mines in Idria is sulphate of magnesia, mixed with a small quantity of sulphate of iron. The hair-salt from the abandoned coal-pits in the neighbourhood of Glasgow is a double salt, composed of sulphate of alumina, and sulphate of iron, in definite proportions; the composition being
1 atom protosulphate of iron, 1½ atom sulphate of alumina, 15 atoms water.
I suspect strongly that the capillary crystals from the schistose alumen of Dioscorides were nearly of the same nature.
From Pliny’s account of the uses to which alumen was applied, it is quite obvious that it must have varied very much in its nature. Alumen nigrum was used to strike a black colour, and must therefore have contained iron. It was doubtless an impure native 105sulphate of iron, similar to many native productions of the same nature still met with in various parts of the world, but not employed; their use having been superseded by various artificial salts, more definite in their nature, and consequently more certain in their application, and at the same time cheaper and more abundant than the native.”
The alumen employed as a mordant by the dyers, must have been a sulphate of alumina more or less pure; at least it must have been free from all sulphate of iron, which would have affected the colour of the cloth, and prevented the dyer from accomplishing his object.
What the alumen rotundum was, is not easily conjectured. Dioscorides says, that it was sometimes made artificially; but that the artificial alumen rotundum was not much valued. The best, he says, was full of air-bubbles, nearly white, and of a very astringent taste. It had a slaty appearance, and was found in Egypt or the Island of Melos.
The liquid alumen was limpid, milky, of an equal colour, free from hard concretions, and having a fiery shade of colour. In its nature, it was similar to the alumen candidum; it must therefore have consisted chiefly, at least, of sulphate of alumina.
– Nitre and Carbonate of Soda
Thomsson writes, “the word nitre (רתנ) had been applied by the ancients to carbonate of soda, a production of Egypt, where it is still formed from sea-water, by some unknown process of nature in the marshes near Alexandria. This is evident, not merely from the account given of it by Dioscorides and Pliny; for the following passage, from the Old Testament, shows that it had the same meaning among the Jews: “As he that taketh away a garment in cold weather, is as vinegar upon nitre: so is he that singeth songs to a heavy heart.” Vinegar poured upon saltpetre produces no sensible effect whatever, but when poured upon carbonate of soda, it occasions an effervescence. When saltpetre came to be imported to Europe, it was natural to give it the same name as that applied to carbonate of soda, to which both in taste and appearance it bore some faint resemblance. Saltpetre possessing much more striking properties than carbonate of soda much more attention was drawn to it, and it gradually fixed upon itself the term nitre, at first applied to a different salt. When this change of nomenclature took place does not appear; but it was completed before the time of Roger Bacon, who always applies the term nitrum to our nitrate of potash and never to carbonate of soda.”
– Lime and Vinegar
“In the preceding history of the chemical facts known to the ancients, I have taken no notice of a well-known story related of Cleopatra. This magnificent and profligate queen boasted to Antony that she would herself consume a million of sistertii at a supper. Antony smiled at the proposal, and doubted the possibility of her performing it. Next evening a magnificent entertainment was provided, at which Antony, as usual, was present, and expressed his opinion that the cost of the feast, magnificent as it was, fell far short of the sum specified by the queen. She requested him to defer computing till the dessert was finished. A vessel filled with vinegar was placed before her, in which she threw two pearls, the finest in the world, and which were valued at ten millions of sistertii; these pearls were dissolved by the vinegar and the liquid was immediately drunk by the queen. Thus she made good her boast, and destroyed the two finest pearls in the world. This story, supposing it true, shows that Cleopatra was aware that vinegar has the property of dissolving pearls. But not that she knew the nature of these beautiful productions of nature. We now know that pearls consist essentially of carbonate of lime, and that the beauty is owing to the thin concentric laminæ, of which they are composed.”
“Nor have I taken any notice of lime with which the ancients were well acquainted, and which they applied to most of the uses to which the moderns put it. Thus it constituted the base of the Roman mortar, which is known to have been excellent. They employed it also as a manure for the fields, as the moderns do. It was known to have a corrosive nature when taken internally; but was much employed by the ancients externally, and in various ways as an application to ulcers. Whether they knew its solubility in water does not appear; though, from the circumstance of its being used for making mortar, this fact could hardly escape them. These facts, though of great importance, could scarcely be applied to the rearing of a chemical structure, as the ancients could have no notion of the action of acids upon lime, or of the numerous salts which it is capable of forming. Phenomena which must have remained unknown till the discovery of the acids enabled experimenters to try their effects upon limestone and quicklime. Not even a conjecture appears in any ancient writer that I have looked into, 109about the difference between quicklime and limestone. This difference is so great that it must have been remarked by them, yet nobody seems ever to have thought of attempting to account for it. Even the method of burning or calcining lime is not described by Pliny; though there can be no doubt that the ancients were acquainted with it.”
What was Handed Down from the Arabians
I quote Thomson’s entire introduction to this chapter which brilliantly reviews the history of the contribution of the Arabians to chemistry, their impact on Europe and the role they plaid in waking Europe up from its slumber during the middle ages. Apart from these, his writing style is brilliant, and I enjoy it so much that I can’t help but give the entire section. He writes, “The people to whom scientific chemistry owes its origin are the Arabians. Not that they prosecuted scientific chemistry themselves, but they were the first persons who attempted to form chemical medicines. This they did by mixing various bodies with each other and applying heat to the mixture in various ways. This led to the discovery of some mineral acids. There they applied to the metals, &c., and ascertained the effects produced upon that most important class of bodies. Thus the Arabians began those research which led gradually to the formation of scientific chemistry. We must therefore endeavour to ascertain the chemical facts for which we are indebted to the Arabians.”
“When Mahomet first delivered his dogmas to his countrymen they were not altogether barbarous. Possessed of a copious and expressive language, and inhabiting a burning climate, their imaginations were lively and their passions violent. Poetry and fiction were cultivated by them with ardour, and with considerable success. But science and inductive philosophy, had made little or no progress among them. The fatalism introduced by Mahomet, and the blind enthusiasm which he inculcated, rendered them furious bigots and determined enemies to every kind of intellectual improvement. The rapidity with which they overran Asia, Africa, and even a portion of Europe, is universally known. At that period the western world, was sunk into extreme barbarism, and the Greeks, with whom the remains of civilization still lingered, were sadly degenerated from those sages who graced the classic ages. Bent to the earth under the most grinding but turbulent despotism that ever disgraced mankind, and having their understandings sealed up by the most subtle and absurd, and uncompromising superstition, all the energy of mind, all the powers of invention, all the industry and talent, which distinguished their ancestors, had completely forsaken them. Their writers aimed at nothing new or great, and were satisfied with repeating the scientific facts determined by their ancestors. The lamp of science fluttered in its socket, and was on the eve of being extinguished.”
“Nothing good or great could be expected from such a state of society. It was, therefore, wisely determined by Providence that the Mussulman conquerors, should overrun the earth, sweep out those miserable governors, and free the wretched inhabitants from the trammels of despotism and superstition. As a despotism not less severe, and a superstition still more gloomy and uncompromising, was substituted in their place, it may seem at first sight, that the conquests of the Mahometans brought things into a worse state than they found them. But the listless inactivity, the almost deathlike torpor which had frozen the minds of mankind, were effectually roused. The Mussulmans displayed a degree of energy and activity which have few parallels in the history of the world: and after the conquests of the Mahometans were completed, and the Califs quietly seated upon the greatest and most powerful throne that the world had ever seen; after Almanzor, about the middle of the eighth century, had 112founded the city of Bagdad, and settled a permanent and flourishing peace, the arts and sciences, which usually accompany such a state of society, began to make their appearance.”
“That calif founded an academy at Bagdad, which acquired much celebrity, and gradually raised itself above all the other academies in his dominions. A medical college was established there with powers to examine all those persons who intended to devote themselves to the medical profession. So many professors and pupils flocked to this celebrated college, from all parts of the world, that at one time their number amounted to no fewer than six thousand. Public hospitals and laboratories were established to facilitate a knowledge of diseases, and to make the students acquainted with the method of preparing medicines. It was this last establishment which originated with the califs that gave a first beginning to the science of chemistry.”
“In the thirteenth century the calif Mostanser re-established the academy and the medical college at Bagdad: for both had fallen into decay, and had been replaced by an infinite number of Jewish seminaries. Mostanser gave large salaries to the professors, collected a magnificent library, and established a new school of pharmacy. He was himself often present at the public lectures.”
“The successor of Mostanser was the calif Haroun-Al-Raschid, the perpetual hero of the Arabian tales. He not only carried his love for the sciences further than his predecessors, but displayed a liberality and a tolerance for religious opinions, which was not quite consistent with Mahometan bigotry and superstition. He drew round him the Syrian Christians, who translated the Greek classics, rewarded them liberally, and appointed them instructors of his Mahometan subjects, especially in medicine and pharmacy. He protected the Christian school of Dschondisabour, founded 113by the Nestorian Christians, before the time of Mahomet, and still continuing in a flourishing state: always surrounded by literary men, he frequently condescended to take a part in their discussions, and not unfrequently, as might have been expected from his rank, came off victorious.”
“The most enlightened of all the califs was Almamon, who has rendered his name immortal by his exertions in favour of the sciences. It was during his reign that the Arabian schools came to be thoroughly acquainted with Greek science; he procured the translation of a great number of important works. This conduct inflamed the religious zeal of the faithful, who devoted him to destruction, and to the divine wrath, for favouring philosophy, and in that way diminishing the authority of the Koran. Almamon purchased the ancient classics, from all quarters, and recommended the care of doing so in a particular manner to his ambassadors at the court of the Greek emperors. To Leo, the philosopher, he made the most advantageous offers, to induce him to come to Bagdad; but that philosopher would not listen to his invitation. It was under the auspices of this enlightened prince, that the celebrated attempt was made to determine the size of the earth by measuring a degree of the meridian. The result of this attempt it does not belong to this work to relate.”
“Almotassem and Motawakkel, who succeeded Almamon, followed his example, favoured the sciences, and extended their protection to men of science who were Christians. Motawakkel re-established the celebrated academy and library of Alexandria. But he acted with more severity than his predecessors with regard to the Christians, who may perhaps have abused the tolerance which they enjoyed.”
“The other vicars of the prophet, in the different Mahometan states, followed the fine example set them by Almamon. Already in the eighth century the sovereigns 114of Mogreb and the western provinces of Africa showed themselves the zealous friends of the sciences. One of them called Abdallah-Ebn-Ibadschab rendered commerce and industry flourishing at Tunis. He himself cultivated poetry and drew numerous artists and men of science into his state. At Fez and in Morocco the sciences flourished, especially during the reign of the Edrisites, the last of whom, Jahiah, a prince possessed of genius, sweetness, and goodness, changed his court into an academy, and paid attention to those only who had distinguished themselves by their scientific knowledge.”
“But Spain was the most fortunate of all the Mahometan states, and had arrived at such a degree of prosperity both in commerce, manufactures, population, and wealth, as is hardly to be credited. The three Abdalrahmans and Alhakem carried, from the eighth to the tenth century, the country subject to the Calif of Cordova to the highest degree of splendour. They protected the sciences, and governed with so much mildness, that Spain was probably never so happy under the dominion of any Christian prince. Alhakem established at Cordova an academy, which for several ages was the most celebrated in the whole world. All the Christians of Western Europe repaired to this academy in search of information. It contained, in the tenth century, a library of 280,000 volumes. The catalogue of this library filled no less than forty-four volumes. Seville, Toledo, and Murcia, had likewise their schools of science and their libraries, which retained their celebrity as long as the dominion of the Moors lasted. In the twelfth century there were seventy public libraries in that part of Spain which belonged to the Mahometans. Cordova had produced one hundred and fifty authors, Almeria fifty-two, and Murcia sixty-two.”
“The Mahometan states of the east continued also to favour the sciences. An emir of Irak, Adad-El-Daula 115by name, distinguished himself towards the end of the tenth century by the protection which he afforded to men of science. To him almost all the philosophers of the age dedicated their works. Another emir of Irak, Saif-Ed-Daula, established schools at Kufa and at Bussora, which soon acquired great celebrity. Abou-Mansor-Baharam, established a public library at Firuzabad in Curdistan, which at its very commencement contained 7000 volumes. In the thirteenth century there existed a celebrated school of medicine in Damascus. The calif Malek-Adel endowed it richly, and was often present at the lectures with a book under his arm.”
“Had the progress of the sciences among the Arabians been proportional to the number of those who cultivated them, we might hail the Saracens as the saviours of literature during the dark and benighted ages of Christianity; but we must acknowledge with regret, that notwithstanding the enlightened views of the califs, notwithstanding the multiplicity of academies and libraries, and the prodigious number of writers, the sciences received but little improvement from the Arabians. There are very few Arabian writers in whose works we find either philosophical ideas, successful researches, new facts, or great and new and important truths. How, indeed, could such things be expected from a people naturally hostile to mental exertion; professing a religion which stigmatizes all exercise of the judgment as a crime, and weighed down by the heavy yoke of despotism? It was the religion of the Arabians, and the despotism of their princes, that opposed the greatest obstacles to the progress of the sciences, even during the most flourishing period of their civilization.103 Fortunately 116chemistry was the branch of science least obnoxious to the religious prejudices of the Mahometans. It was in it, therefore, that the greatest improvements were made: of these improvements it will be requisite now to endeavour to give the reader some idea. Astrology and alchymy, they both derived from the Greeks: neither of them were inconsistent with the taste of the nation—neither of them were anathematized by the Mahometan creed, though Islamism prohibited magic and all the arts of divination. Alchymy may have suggested the chemical processes—but the Arabians applied them to the preparation of medicines, and thus opened a new and most copious source of investigation.”
“The chemical writings of the Arabians which I have had an opportunity of seeing and perusing in a Latin dress, being ignorant of the original language in which they were written, are those of Geber and Avicenna.”
Geber’s Table Salt, Sal ammoniac and Saltpetre used in Curing
I shall now state the different chemical substances or preparations which were known to Geber, or which he describes the method of preparing in his works.
1. Common salt. This substance occurring in such abundance in the earth, and being indispensable as a seasoner of food, was known from the earliest ages. But Geber describes the method which he adopted to free it from impurities. It was exposed to a red heat, then dissolved in water, filtered, crystallized by evaporation, and the crystals being exposed to a red heat, were put into a close vessel, and kept for use. Whether the identity of sal-gem (native salt) and common salt was known to Geber is nowhere said. Probably not, as he gives separate directions for purifying each.
2. Geber gives an account of the two fixed alkalies, potash and soda, and gives processes for obtaining them. Potash was obtained by burning cream of tartar in a crucible, dissolving the residue in water, filtering the solution, and evaporating to dryness. This would yield a pure carbonate of potash.
Carbonate of soda he calls sagimen vitri, and salt of soda. He mentions plants which yield it when burnt, points out the method of purifying it, and even describes the method of rendering it caustic by means of quicklime.
3. Saltpetre, or nitrate of potash, was known to him; and Geber is the first writer in whom we find an account of this salt. Nothing is said respecting its origin; but there can be little doubt that it came from India, where it was collected, and known long before Europeans were acquainted with it. The knowledge of this salt was probably one great cause of the superiority of the Arabians over Europeans in chemical knowledge; for it enabled them to procure nitric acid, by means of which they dissolved all the metals known in their time, and thus acquired a knowledge of various important saline compounds, which were of considerable importance.
There is a process for preparing saltpetre artificially, in several of the Latin copies of Geber, though it does not appear in our English translation. The method was to dissolve sagimen vitri, or carbonate of soda, in aqua fortis, to filter and crystallize by evaporation. If this process be genuine, it is obvious that Geber must have been acquainted with nitrate of soda; but I have some doubts about the genuineness of the passage, because the term aqua fortis occurs in it. Now this term occurs nowhere else in Geber’s work: even when he gives the process for procuring nitric acid, he calls it simply water; but observes, that it is a water possessed of much virtue, and that it constitutes a precious instrument in the hands of the man who possesses sagacity to use it aright.
4. Sal ammoniac was known to Geber, and seems to have been quite common in his time. There is no evidence that it was known to the Greeks or Romans, as neither Dioscorides nor Pliny make any allusion to it. The word in old books is sometimes sal armoniac, sometimes sal ammoniac. It is supposed to have been brought originally from the neighbourhood of the temple of Jupiter Ammon: but had this been the case, and had it occurred native, it could scarcely have been unknown to the Romans, under whose dominions that part of Africa fell. In the writings of the alchymists, sal ammoniac is mentioned under the following whimsical names:
Aqua duorum fratrum ex sorore,
Lapis angeli conjungentis,
Geber not only knew sal ammoniac, but he was aware of its volatility; and gives various processes for subliming it, and uses it frequently to promote the sublimation of other bodies, as of oxides of iron and copper. He gives also a method of procuring it from urine, a liquid which, when allowed to run into putrefaction, is known to yield it in abundance. Sal ammoniac was much used by Geber, in his various processes to bring the inferior metals to a state of greater perfection. By adding it or common salt to aqua fortis, he was enabled to dissolve gold, which certainly could not be accomplished in the time of Dioscorides or Pliny. The description, indeed, of Geber’s process for dissolving gold is left on purpose in a defective state; but an attentive reader will find no great difficulty in supplying the defects, and thus understanding the whole of the process.
About Nitric Acid, he writes: Nitric acid was known to him by the name of dissolving water. He prepared it by putting into an alembic one pound of sulphate of iron of Cyprus, half a pound of saltpetre, and a quarter of a pound of alum of Jameni: this mixture was distilled till every thing liquid was driven over. He mentions the red fumes which make their appearance in the alembic during the process. This process, though not an economical one, would certainly yield nitric acid; and it is remarkable, because it is here that we find the first hint of the knowledge of chemists of this most important acid, without which many chemical processes of the utmost importance could not be performed at all.
This acid, thus prepared, he made use of to dissolve silver: the solution was concentrated till the nitrate of silver was obtained by him in a crystallized state. This process is thus described by him: “Dissolve silver calcined in solutive water (nitric acid), as before; which being done, coct it in a phial with a long neck, the orifice of which must be left unstopped, for one day only, until a third part of the water be consumed. This being effected, set it with its vessel in a cold place, and then it is converted into small fusible stones, like crystal.”
He was in the habit also of dissolving sal ammoniac in this nitric acid, and employing the solution, which was the aqua regia of the old chemists, to dissolve gold.124 He assures us that this aqua regia would dissolve likewise sulphur and silver. The latter assertion is erroneous. But sulphur is easily converted into sulphuric acid by the action of aqua regia, and of course it disappears or dissolves.
The Salts of Geber NOT used in Curing
Attfield, John (1871)
NITRIC ACID AND OTHER NITRATES.
Formula of Nitric Acid HNO3. Molecular weight 63.
-The group of elements represented by the formula NO3 is that characteristic of nitric acid and all other nitrates; hence it is expedient to regard these elements as forming an acidulous radical, which may be termed the nitric radical. Like the hypothetical basylous radical ammonium (NH4), this supposed acidulous radical (NO:) has not been isolated. Possibly it is liberated when chlorine is brought into contact with nitrate of silver; but if so, its decomposition into white crystalline nitric anhydride (N2O5) and oxygen (0) is too rapid to admit of its identification.
Sources.-The nitrogen and oxygen of the air combine and ultimately form nitric acid whenever a current of electricity (as in the occurrence of lightning) passes. Nitrates are commonly met with in waters, soils, and the juices of plants. In the concentrated plant juices termed medicinal ” Extracts,” small prismatic crystals of nitrate of potassium may occasionally be observed. (The cubical crystals often met with on extracts are chloride of potassium.) Nitric acid and other nitrates are obtained from nitrates of potassium and sodium, and these from the surface soil of tropical countries. Nitrate of potassium or prismatic nitre (from the form of its crystals) is chiefly produced in and about the villages of India. The natives simply scrape the surface of waste grounds, mud heaps, banks, and other spots where a slight incrustation indicates the presence of appreciable quantities of nitre, mix the scrapings with wood-ashes (carbonate of potassium, to decompose the nitrate of calcium always present), digest the mixture in water, and evaporate the liquor. The impure product is purified by careful recrystallizations, and is sent into commerce in the form of white crystalline masses or fragments of striated six-sided prisms. Besides its use in medicine (Potassii Nitras, U. S. P.), it is employed in very large quantities in the manufacture of gunpowder. Nitrate of Sodium (Sodii Nitras, U. S. P.) occurs in more distinct incrustations on the surface of the ground in Peru, Bolivia, and Chili, more especially in the district of Atacama; it is distinguished as Chili saltpetre or (from the form of its crystals-obtuse rhomboids) cubic nitre, and is chiefly used as a manure and as a source of nitric acid, its tendency to absorb moisture unfitting it for use in gunpowder. In many parts of Europe nitrate of potassium is made artificially by exposing heaps of animal manure, refuse, ashes, and soil to the action of the air and the heat of the sun: in the course of a year or two the nitrogen of the animal matter becomes oxidized to nitrates, and the latter are removed by washing.
Note. —The word nitric is from nitre, the English equivalent of the Greek vatpov (nitron), a name applied to certain natural deposits of natron (carbonate of sodium), for which nitrate of potassium seems at first to have been mistaken. Saltpetre is simply sal petrce, salt of the rock, in allusion to the natural origin of nitrate of potassium. Sal prunella (from sal, a salt, and pruna, a live coal) is nitrate of potassium melted over a fire and cast into cakes or bullets. The nitric radical is univalent (NO3′).
NITROUS ACID (HNO2) AND OTHER NITRITES.
— Strongly heat a fragment of nitrate of potassium or of sodium on a piece of platinum foil; oxygen is evolved and nitrite of potassium remains. Test.-Dissolve the residue in water, add a few drops of dilute sulphuric acid, then a little weak solution of iodide of potassium, and, lastly, some mucilage of starch; the deep-blue compound of iodine and starch is at once produced. Repeat this experiment, using nitrate of potassium instead of nitrite; no blue color is produced. 2HI + 2HNO2 = 2H120 + 2NO + I2. Testfor Nitrites in VWater.-This liberation of iodine by nitrites and not by nitrates is a reaction of considerable value in searching for nitrites in ordinary drinking-waters, the occurrence of such salts being held to indicate the presence of nitrogenous organic matter in a state of oxidation or decay. The sulphuric acid used in the operation must be pure, and the iodide of potassium free from iodate. Commercial Nitrous Acid.-The liquid commonly termed in pharmacy nitrous acid is simply nitric acid impure from the presence of nitrous acid. The only nitrite used in medicine is a nitrite of an organic basylous radical, ethyl; nitrite of ethyl (C2HNO,), or nitrous ether, is the chief constituent of ” sweet spirit of nitre” (Spiritus.Etheris Nitrosi, B. P. and U. S. P.: vide Index).
The History of Chemistry by Thomas Thomson, M.D. F.R.S.E. Professor of Chemistry in the University of Glasgow. In Two Volumes. Vol. I. London: Henry Colburn, and Richard Bently, New Burlington Street. 1830. Whiting, Beaufort House, Strand.
Attfield, John. (1871) Chemistry, general, medical, and pharmaceutical, including the chemistry of the U.S. pharmacopœia. A manual on the general principles of the science, and their applications to medicine and pharmacy. By John Attfield. Philadelphia: H. C. Lea,