Introduction to Bacon & the Art of Living
The story of bacon is set in the late 1800s and early 1900s when most of the important developments in bacon took place. The plotline takes place in the 2000s with each character referring to a real person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes and practices are superimposed on a historical setting. Modern people interact with old historical figures with all the historical and cultural bias that goes with this.
narrative – the history of bacon
From Sea to Deserts -> Sal Ammoniac Predating Saltpetre
University Geology Museum (1), Copenhagen, June 1891
Dear Children,
The day has finally arrived, our much-anticipated visit to the University of Copenhagen’s Geology Museum. It is in Nørregade. The museum is part of the Natural History Museum of Denmark. It was exceptional. The exhibition of minerals is, from what I am told, one of the finest in Europe! There are exhibitions on meteorites, volcanoes, continental drift, the geology of Denmark, the geology of Greenland, fossils (including the largest bivalves such as clams, mussels, oysters, and scallops), and an exhibition on the origin of humans. The fact that we had to postpone the trip for a week worked out well. Despite Uncle Jeppe being unable to join us, the Curator of the Museum was there and what happened was beyond our expectations! He proved to be just the man to be bombarded with my many questions!
Bezeklik caves on mountain slopes near Turfan
The Curator and My Research Partner
It was just a stroke of luck that the curator of the museum was on duty himself. Dr Hans Thirsten is a scientist with a single-minded dedication to the earth we live on. (2) He agreed to have coffee with us and answer our questions. This is the thing about the Danish that I notice wherever I go – they don’t have inflated egos and it is true of Dr Hans. If this were in Cape Town, I cannot imagine that someone with his position would have taken the time to have coffee with us and answer so many questions from a novice about minerals, chemistry, and geology. Minette is the right research partner! She asks simple but powerful questions. She is never afraid to ask for clarification on points of seeming contradiction.
From Sea to Dry Deserts
Dr Hans patiently listened to my questions before he started speaking. He was very polite in letting me finish and then he was also polite enough to completely disregard them and start at a place I had no knowledge of. Eventually, he returned to the specifics of my questions but in an unexpected way. Not one of us minded his approach. It was all fascinating and he had Minette, Andreas, his dad, his mom, and me hanging on to his every word.
First, the professor had to set me right in a wrong perception I had about how salts naturally occur on earth. I did not understand that today our salts are very refined. Impurities are removed before it is sold. Different salts are neatly separated but in nature that is not how they occur. In nature, salt exists as a mixture of various minerals. When the ancients talked about saltpetre, for example, there were many different grades of purity. The nitrate salts may be mixed with what we refer to as table salt or sodium chloride along with many other chemical compounds. The opposite also occurs. If salt is mined from a salt pan, for example, there may be nitrate salts mixed in.
The other matter that he cleared up is that of terminology. Different civilisations referred to the same salt by different names and sometimes used the same name to refer to different salts. This means that the historical consideration of minerals and salts must be done carefully, and one must always look at the characteristics of the salts described and not assume the term is used with the modern understanding.
With these initial thoughts, Dr Hans continues. “The real question relates to sources of nitrogen that could potentially end up as nitric oxide in meat which you know is the actual curing molecule and not nitrate or nitrite.” His knowledge of meat curing was based on his general knowledge of the subject matter, and it was vast!
“In this regard, everywhere and anywhere we have to do with any of the various forms of nitrogen in nature, we have a possible source for meat curing. Since nitrate is far more stable than nitrite, which acts only as an intermediate species of nitrogen and since nitric oxide is a gas, the most stable source of nitrogen will be in the form of a nitrate salt such as potassium nitrate or sodium nitrate. All salts eventually end up in the sea and one would expect the sea to be a large source of nitrate. It is therefore not surprising that while people living in desert areas would have noticed certain salts to have the ability to change the colour of meat from brown, back to pinkish/ reddish, along with increased preservation power and a slightly distinct taste, it is certainly true that coastal dwellers would have observed it first.”
“Well, Dr Hans said, “of course, this is only partially true. The presence of nitrates in the sea is primarily due to the nitrogen cycle, involving biological processes like nitrification and denitrification. Nitrate salts are found on land in arid regions where water could not carry it away such as Chilean saltpetre found in the Atacama desert which is one of the driest regions on earth”.
“The presence of nitrate and nitrite in sea salt is minimal, typically less than 2ppm, making it unlikely that sea salt alone was responsible for observed meat curing effects. Some speculate that it was the practice of seaside communities who stored meat in sea water that led to the discovery of curing. The practice of preserving meat by storing it in water, including seawater, might have directly led to the formation of significant amounts of nitrate and nitrite, but not on its own. For sufficient amounts of nitrite and nitrate ions to be formed, bacteria had to be involved. When stored in water, proteins in meat can undergo ammonification, resulting in the release of ammonia.”
“The process is described as follows: Proteins in meat are complex molecules made up of amino acids linked by peptide bonds. Over time, especially after the death of the animal, these proteins begin to break down. Bacteria contribute to this. Bacteria present on the meat or in the environment produce enzymes that catalyze the breakdown of proteins into smaller components, including amino acids. Specific enzymes, such as proteases, catalyze the hydrolysis of proteins. Hydrolysis is a chemical process that involves the cleavage of bonds in molecules due to the addition of water. Once proteins are broken down into amino acids, another process called deamination occurs. In deamination, the amino group (-NH2) from amino acids is removed, forming ammonia (NH3) and a keto acid.”
“Endogenous enzymes or enzymes inherently part of the meat itsef have a significant contribution in the breakdown of proteins. After the animal is killed, a process called autolysis begins, where the meat’s own enzymes start breaking down muscle tissue. This is a natural part of meat aging and tenderization. Proteolytic Enzymes are the key enzymes in meat that break down proteins. They include cathepsins and calpains, which are naturally present in the muscle tissue. These enzymes become more active after the animal’s death and contribute significantly to the breakdown of muscle proteins into smaller peptides and amino acids. Endogenous enzymes are primarily responsible for the tenderization of meat during aging. They work by breaking down muscle fiber proteins, connective tissue proteins (like collagen), and other structural proteins.”
“Microbial enzymes or enzymes produced by bacteria are also very important in the process. When meat is exposed to bacteria, either from the environment or from contamination, these bacteria can produce their own proteases. These enzymes further break down proteins in the meat. In conditions favourable for bacterial growth (like in the presence of water, nutrients, and suitable temperatures), bacterial enzymes can significantly contribute to the breakdown of meat proteins. This process often leads to spoilage and off-flavours, especially if pathogenic or spoilage bacteria are involved. The bacterial enzymes can also contribute to the deamination process, where amino acids are broken down, releasing ammonia which is our primary interest because the ammonia will lead to nitrite and nitrate which will cure the meat.”
“In combination, these enzymes will have a powerful effect. In the context of meat stored in water, both endogenous and microbial enzymes can be active. The water provides an ideal medium for enzymatic activity and bacterial growth, accelerating protein breakdown and ammonification. The extent to which each type of enzyme contributes to protein breakdown depends on factors like the age of the meat, storage conditions, temperature, and the presence or absence of specific bacteria.”
“You can see that the fact that the meat is stored in water is important since water provides an essential medium for enzymatic activities which is what the surface proteins would be in contact with. Water would also help with bacteria. Water acts as a solvent, supporting the growth and proliferation of bacteria. The more bacteria present, the more enzymatic activity there is to break down proteins as the bacteria will produce the enzymes. Water further allows for the easy transport of enzymes and nutrients, facilitating the interaction between microbial enzymes and the proteins in meat.
Now, bacteria is responsible for converting the ammonia to nitrite and then to nitrate in steps that are called nitration and nitrification (conversion of ammonia to nitrite, and nitrite to nitrate, respectively). Ammonia-oxidizing bacteria (AOB), if present on the meat or in the environment (including seawater), can convert ammonia into nitrite (NO2-). This process is known as nitritation. Bacteria involved in nitrification are commonly found in various environments, including soil and water. It’s plausible that some of these bacteria could be present on the surface of the meat or in the storage environment. In a second step, nitrite-oxidizing bacteria (NOB) can then convert nitrite into nitrate (NO3-). This is the second step of nitrification, known as nitratation. The presence of nitrite and nitrate on meat, even in small quantities, can have preserving effects. Nitrite, in particular, is effective in inhibiting the growth of harmful bacteria, and in contributing to the characteristic flavour and colour of cured meats.”
Dr Hans ordered a second cup of strong coffee! His mannerism is controlled and he speaks in an almost monotone voice. We all remained spellbound. I could not even look up as I was furiously trying to keep up taking notes and I was thankful every time he paused to take a sip of his coffee. “I suspect that people discovered this even long before barrels were invented. In general, coastal communities used seawater for meat storage and the practice was so widespread that it would have been impossible not to have noticed meat curing taking place. If it is generally true that the earliest humans first settled around coastal locations before migrating inland, it could push the discovery of curing many thousands of years earlier than we ever imagined, to a time when modern humans started spreading around the globe. The process I described of forming ammonium and bacteria converting the ammonia into nitrite and nitrate is also true for fresh water. The fact that the seawater contains some salt had nothing to do with it. More important, is the type of bacteria found in the seawater but the same bacteria would also be present in freshwater. The fact is still that nitrate and nitrite would be generally “closer” to the communities living by the sea in sea salt whether it was collected from the bay or through solar evaporation, from regular seawater as nitrogen is an important nutrient in the water for microorganisms and plants in the water, alike.”
“When it developed into an art or a trade is another question altogether, but, speculating about this, I think we can safely push the time when it was noticed back to the earliest cognitive and cultured humans whom we would have recognized as thinking “like us” if we could travel back in time and meet them. I think the question of when they recognised this in various regions to the time when these areas were populated.”
“Even though I now suspect that curing was first noticed by communities living by the sea as I just explained, I suspect inland dwellers discovered salt that cures meat in deserts also. As I already said, salt in nature almost always appears as a mix of various salts and under certain conditions, these salt deposits contain small amounts of nitrate salts, ammonium chloride and sometimes even nitrite. The ancients would have noticed that these salts cure meat. We mostly think of saltpetre as the earliest curing salt from the desert, but I think there is another salt that possibly pre-dates the widespread use of saltpetre as curing agent and that is sal ammoniac.”
Sal Ammoniac
“The most important two curing salts that appear to us from antiquity are saltpetre (sodium or potassium nitrate) and sal ammoniac (ammonium chloride). Both salts were well known in Mesopotamia and references to them appear alongside references to salt curing of fish mentioned earlier and both salts were used in meat curing. I have already shown you the link between ammonia and nitrite from our discussion on the breakdown of amino acids from surface protein of meat stored in water. The use of sal ammoniac, you will therefore see, makes perfect sense!”
I was riveted! “The ancients developed basic techniques of separating out the different salts. In particular, sal ammoniac was by far the more important salt of the bronze age (2000 BCE). It was produced in Egypt where it appeared around the kilns where camel dung was used as fuel for the fire and it was mined in Asia. When the horse was domesticated around 5000 BCE, a food source was needed to sustain humans on long expeditions and I believe sal ammoniac fits the requirement perfectly.”
“Both salts cure the meat in a week which obviously had huge advantages compared to salting the meat with normal table salt. In my experience, salt ammoniac is, however, a far better preservative than saltpetre. Sal ammoniac, as far as I can find, was globally traded much earlier than saltpetre. Ancient Macedonian records indicate that even in 2000 BCE saltpetre was preferred in food over sal ammoniac on account of the better taste of saltpetre. Still, sal ammoniac was far more vigorously traded than saltpetre in the early Christian era and possibly for thousands of years before that. As is the case we discussed in seawater, ammonium chloride undergoes a bacterial transformation into nitrites which will then in the meat matrix yield nitric oxide which will cure the meat. Using sal ammoniac directly would result in quicker curing of the meat than leaving the meat in water, sea water or fresh.”
Natural Sal Ammoniac
Sal ammoniac is a salt that both occurs naturally and is made by human endeavour. He introduced us to a region of the word that I did not even know existed. “Turpan is the name of an oasis in the far western regions of China. It is an extremely dry area. Turpan is also probably the only place on earth where sal ammoniac and nitrate salts in the form of sodium nitrate occur in massive quantities side by side. Sal ammoniac, in the surrounding mountains and nitrate salts on the basin floor.
“Chinese authors of antiquity are unanimous that sal ammoniac came into China from Turpan, Tibet, and Samarkand and through Samarkand, it was traded into the Mediterranian along the Silk Road. It all makes for an appealing case for sal ammoniac as the actual curing salt from antiquity that was used in meat curing when the practice spread around the world. There is even a tantalizing link between Turfpan and the ancient city of Salzburg and the salt mines which leads me to speculate that the trade of sal ammoniac was done into the heart of Western Europe, into what became known as Austria. This leads me to believe that the actual technological progressions related to meat curing may have come from Austria. Whether it was through Salzburg and initially from Turfan is not clear.”
“Around Turpan (also called Turfan), sal ammoniac forms in volcanic vents and after volcanic eruptions before it has rained which dissolves the crystals. It is highly soluble. It is unique in that the crystals are formed directly from the gas fumes and bypass the liquid phase, a process known as sublimation. The Turfan area, both the basin and the mountains are replete with different salts containing nitrogen (nitrate salts and ammonium) any one of which could be used effectively in meat curing.”
“The sal ammonia was mined from openings in the sides of volcanic mountains where steam from underground lava flows created the ammonium chloride crystals. These were traded across Asia, Europe and into India. Massive sodium nitrate deposits occur in the Tarim Basin, the second-lowest point on earth. I then speculate that traders used some of these deposits to forge ammonium chloride since the ammonium chloride crystals did not survive in crystal form on long voyages due to their affinity for water which breaks the crystal structure down. Once this happened, the sodium nitrate and the ammonium chloride look similar. Because it is known that almost all the sal ammonia produced in Samarkand was exported, I deduce that demand outstripped supply and this provided the incentive for such forgery. I find support for the likelihood of such a forgery, not just in the limited supply of sal ammoniac compared to nitrate salts, but also in the fact that mining sal ammoniac was a seasonal affair and extremely dangerous and a difficult undertaking.”
“It seems likely that sal ammonia was the forerunner of saltpetre as the curing agent of choice. It is composed of two ions, ammonium, and chloride. The ammonium would be oxidized by ammonia-oxidizing bacteria (AOB) into nitrites and the well-known reaction sequence would follow.”
“Sal ammoniac was mined from the earth. In China, ancient names given for Sal Ammoniac are “red gravel” and “essence of the white sea.” There were sal ammoniac mines in Soghd. Mohammadan traders passed it at Khorasan travelling towards China. Kuča still yielded sal ammoniac at the beginning of the 1900s. There are ancient references to white and red varieties of sal ammoniac. The mines in Setrušteh or سمرقند (Samarkand in the Persian language) are described in classic literature as follows. “The mines of sal ammoniac are in the mountains, where there is a certain cavern, from which a vapour issues, appearing by day like smoke, and by night like fire. Over the spot whence the vapour issues, they have erected a house the doors and windows of which are plastered over by clay that none of the vapour can escape. On the upper part of this house the copperas rest. When the doors are to be opened, a swiftly-running man is chosen, who, having his body covered over with clay, opens the door; takes as much as he can from the copperas, and runs off; if he should delay he should be burnt. This vapour comes forth in different places, from time to time; when it ceases to issue from one place, they dig in another until it appears, and then they erect that kind of house over it; if they did not erect this house, the vapour would burn, or evaporate away.” (Laufer,1919) “Tibetans received this salt from India as can be seen from an ancient name they gave to it namely “Indian salt.” There are records that it was harvested from certain volcanic springs from Tibet and Se-č’wan. (Laufer,1919) The same vapours are seen in the smokey mountains of Turfan.”
Human-Made Ammonium Chloride
“Just like saltpetre, sal ammoniac occurs naturally and is also generated by human ingenuity. The name, ammonia, came from the ancient Egyptian god, Amun. The Greek form of Amun is Ammon. At the temple dedicated to Ammon and Zeus near the Siva Oasis in Lybia, priests and travellers would burn soil rich in ammonium chloride. The ammonium chloride is formed from the soil, being drenched with nitrogen waste from animal dung and urine. The ammonia salts were called sal ammoniac or “salt of ammonia” by the Romans because the salt deposits were found in the area. During the Middle Ages, ammonia was made through human endeavour through the distilling of animal dung, hooves, and horns. (Myers, RL. 2007: 27)”
“The New York Tribune of 31 January 1874 wrote the following. ‘For centuries sal ammoniac was imported from Egypt where it is sublimed from camels’ dung.’ An article, published in 1786 on Friday, 18 August in the Pennsylvania Packet, described the process of making sal ammoniac in Egypt as follows.’Sal Ammoniac is made from soot arising from the burnet dung of four-footed animals that feed only on vegetables. But the dung of these animals is fit to burn for sal ammoniac only during the four first months of the year when they feed on fresh spring grass, which, in Egypt is a kind of trefoil or clover; for when they feed only on dry meat, it will not do. The dung of oxen, buffalo, sheep, goats, horses, and asses, are at the proper time as fit as the dung of camels for this purpose; it is said that even human dung is equal to any other.'”
“The soot arising from the burnt dung is put into glass vessels, and these vessels into an oven or kiln which is heated by degrees and at last urged with a very strong fire for three successive nights and days, the smoke first shows itself, and, in a short time after, the salt appears sticking to the glasses, and, by degrees, covers the whole opening. The glasses are then broken, and the salt is taken out in the same state and form in which it is sent to Europe. At this time, Egypt was one of the major suppliers of sal ammoniac to the European continent.”
Ammonium Chloride (Sal Ammoniac) Chemistry
“We have seen that nitrite is formed by removing an oxygen atom from nitrogen. It was the Russian microbiologist Sergei Winogradsky who discovered that certain microorganisms create nitrite and nitrate from ammonia through a process called biological oxidation. Have a look at how oxygen is added at every step. Ammonia is NH3 and there is no oxygen. Nitrite is formed (NO−2 ) which is the nitrogen and two oxygen atoms. From nitrite, through bacterial action, nitrate is formed (NO−3). We have to understand a bit more about ammonia to see how this works. This will be very important when we look at the decomposition of animal tissue and in animal urine and excrement since it contains copious amounts of ammonia. The building blocks of ammonia are seen in its chemical formulation. Ammonia is a compound of nitrogen and hydrogen with the formula NH3. In nature, ammonia exists as NH3 or its ammonium ion (NH4+). The ammonium ion, in nature, also combines with a metal such as chlorine to form a salt of ammonium. Ammonium is therefore not only important in the nitrogen cycle but also in meat curing in the form of a salt where a metal such as chloride combines with the ammonium ion to form ammonium chloride (NH4Cl). It is the NH4 that makes it mildly acidic and the new molecule of sal ammoniac or ammonium chloride is highly reactive with water. Ammonium chloride occurs naturally as a crystal and is formed through the action of bacteria on decomposing organic material. As a salt, it is one of the iconic salts of antiquity.
“Not only would it result in the reddish-pinkish cured colour, but it was an excellent preservative. An 1833 book on French cooking, The Cook and Housewife’s Manual by Christian Isobel Johnstone states that “crude sal ammonia is an article of which a little goes far in preserving meat, without making it salt.” (Johnstone, C. I.; 1833: 412) It is, of course, the sodium which tastes salty in sodium chloride and ammonium chloride will have an astringent, salty taste. I know exactly what ammonium chloride tastes like since it was added to my favourite Dutch candy “Zoute Drop” with liquorice.”
The Turfan Priority
“The reason for the interest in the Turfan region, as with the Atacama region in Chili and Peru where massive nitrate deposits exist was in the first place the existence of the oldest naturally mummified human bodies. In both the Atacama region and the Turfan depression, natural mummification occurred as a result of the driest climate on earth and the very cold nighttime temperatures, but also due to the natural presence of nitrate in the soil. The link between what the people observed in their relatives not decaying and the salts that contributed to this was obvious to the inhabitants of these regions. Besides this, Turfan was a major trading location with ample contact with the rest of the world for them to know how unusual this is.”
Dr Thirsten pulled the curtains of his thoughts back as he sat, relaxed in a comfortable chair and looked at all the evidence he considered over the years. He thinks that Turfan plays a role in changing nitrite curing into an art. The first and obvious reason is the fact that such large deposits of nitrate exist in the depression and in contrast to the huge quantities that exist in the Atacama Desert, these deposits occur on the top layer of the soil making it much more accessible. His second reason is the occurrence of sal ammoniac in close proximity to nitrate. The fact is that these are two completely different salts and despite the tantalising possibility of the one being traded for the other, people in the region must have developed the skill from early on to distinguish between the two. There is evidence that the different salts were often confused, but a basic understanding of the distinct properties of each salt would have developed among the population. Evidence from Turfan shows that sal ammoniac was one of the most traded commodities.
A third clue is evidence of a sophisticated understanding of nitrate salt as medicine in the general proximity of Turfan. This comes to us from a city about 800km to the east, Dunhuang.
On 25 June 1900, a Daoist monk, Wang Yuanlu, discovered a manuscript in the Mogao caves close to Dunhuang. It is a mix of religious and secular documents dating from the 5th to the early 11th centuries. One text is of particular interest to us, referred to as the Dunhuang Medical Text. The text is attributed to the famous Daoist alchemist and physician Toa Hongjing (CE 456 – 536). (Cullen, C, Lo, V.; 2005) There is evidence that it relies on earlier traditions from the Han and Sui Dynasties. “The original was decorated with images of the Three Daoist Lords and the Twelve Constellations, indicating links with Doist traditions.” In translation, it reads as follows:
“The symptoms presented by the patient point to some sort of cardiovascular distress. The colour of the fingernails (cyanosis) indicates a lack of oxygen in the tissue caused by restricted blood flow. Cold hands and feet point to the same. The pain suffered by the patient may indicate severe angina, i.e. restricted blood flow due to the narrowing of the cardiac arteries.”
What is completely unexpected is that the value of bacterially reduced nitrate has been known since antiquity. Dr Thirsten speculated on his part that he would not be surprised if science discovers that there is a physiologically important role of nitrite for humans and possibly for all mammals. The Chinese did not know anything about bacteria that reduce nitrate to nitrite, but by careful observation, they knew that nitrate salt that is kept in the month changes into something with extraordinary healing power. (3)
An Unforgettable Day
It was all over too soon. When Dr Hans was done, everybody applauded! I asked him how he knew so much about meat curing and not only geology and mineralogy. He told me that he grew up in a butcher’s family. His dad had a keen interest in mineralogy in particular since it deals with chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artefacts. His father inspired him to study geology.
That evening we did not read Edward Smith’s book after supper. Instead, we went over the notes I took and where our host was too fast for me to catch everything he said, Minette helped me to get the facts straight. She has a very keen mind and a great memory.
We talked till very late into the night and all retired to bed, aware that we all experienced something very special today. There were two groups of people that I wanted to share this with. Tristan, Lauren, I could not go to bed without writing this letter. It is now 2:00 a.m. Tomorrow I will share this with someone else. Jeppe could not attend on account of the birthday celebrations of a grandchild. I can hardly wait for Minette and me to share this with him.
Now I am off to bed! I am exhausted but insanely excited! My Danish experience had just gone to another level! I can hardly believe the privilege I have to be here!
Lots of love from Denmark and a very happy father!
Dad
Notes on the Elucidation of the Mechanism behind the Dunhuang Medical Text
“Modern treatment for angina is glyceryl trinitrate or isosorbide dinitrate. So, at first glance, there seems to be a similarity in treatment, compared to the one described in the Dunhuang Medical Text but these are organic nitrates which can be used by the body to resolve the restricted blood flow. It does this by converting it through enzymes into nitric oxide. Saltpetre is inorganic and by itself will not have any effect to relieve the symptoms. The body does not have enzymes that will convert nitrate to nitric oxide which is the agent responsible for initiating the sequence that leads to a resolution of the restricted blood flow.”
“The remarkable feature of the Dunhuang text is that the combination of the use of saltpetre (which is nitrate), not on its own, but when applied according to the dictates of the text, which then becomes a remedy for exactly the condition described. Under very special circumstances, exactly as detailed in the Dunhuang text, beginning with the microbial conversion of nitrate to nitrite by bacteria on the tongue, the nitrate ion from saltpetre converts into a species which can be changed in the body to nitric oxide which resolves the symptoms. This molecule is nitric oxide. An interesting side note is that the tongue, in traditional Chinese medical theory, is linked to the function of the heart.”
Further Reading
From The Salt Bridge,
01. Salt – 7000 years of meat-curing
02. Nitrate salt’s epic journey: From Turfan in China, through Nepal to North India
03. And then the mummies spoke!
06. Ancient plant Curing of Meats
07. The Turfan Depression links with the Black Sea Region
(c) eben van tonder
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Note 1
Neither the University of Copenhagen, the Geology Museum nor any other affiliated organisation had any input in any of the content in this chapter. All research and conclusions are that of Eben van Tonder and the interaction with the curator of the museum, as portrayed here, is fiction. Eben places it in this setting for literary and artistic reasons.
Note 2
Hans Thirsten is a reference to Hans Thybo whom we did not meet nor was he ever the curator of the museum. I, however, want to honour Hans Thybo as an exceptional scientist and an unusually talented man by mentioning his name in this work. The entire discussion is based on my own work. To prevent any direct reference to him I changed his surname completely, but I want to mention on whom I base this character. I quote an excellent background of Dr Thybo from Wikipedia which reads:
Hans Thybo (born 19 February 1954) is a Danish geophysicist and geologist. He was a Professor of Geophysics at the Geological Institute and the Institute for Geography and Geology at the University of Copenhagen, as well as at the Centre for Earth Evolution and Dynamics at the University of Oslo. He is a professor at the Eurasia Institute of Earth Sciences at Istanbul Technical University and at the School of Earth Sciences at China University of Geosciences, Wuhan. Until a fusion in 2007, he was elected Head of the Department at the Geological Institute and a member of the board of Geocenter Copenhagen. He was a Professor at the Department of Geosciences and Natural Resource Management until he was dismissed from his Chair in 2016. The dismissal was later found illegal and violating employment agreements by an arbitration court and Thybo received a modest economic compensation, but the University of Copenhagen did not re-employ Thybo, nor did the University sanction his accusers. The internationally agreed principle of tenure for university professors does not apply to universities in Denmark. Thybo has earlier been associated with Technische Hogeschool Delft and Stanford University.
Thybo is President of the International Lithosphere Program (ILP) and was earlier President of the European Geosciences Union, where he also held posts as General Secretary and President for the Seismology Division. He has been chair of the Danish national committee for ICSU (International Council for Science). He is currently a member of the Committee for Freedom and Responsibility in Science of ISC (International Science Council). He is a member of and was earlier vice president of Royal Danish Academy of Science and Letters. He has received the 1000 Talents Award from China and he is a fellow of Royal Astronomical Society, London and the Geological Society of America. He is elected member of Academia Europaea, the Norwegian Academy of Sciences and Letters and the Danish Academy of Natural Sciences, and he has been a Danish representative to the International Council for Science (ICSU).
Hans Thybo has been a leader of several geoscientific research programs and he has been a field expedition leader to e.g. the ice sheet in Greenland, east Africa and Siberia. He initiated several pan-European research programmes with east-west collaboration after the end of the Cold War. His research includes the discovery of ca. 2 billion-year-old plate tectonic structures, the fundamental Mid-Lithospheric Discontinuity of the lithospheric mantle, the presence of molten rocks at the Core-Mantle Discontinuity at ca. 3000 km depth below Siberia, a new model for the formation of the economically important sedimentary basins, Presence of strong seismic anisotropy in cratonic crust with the implication that crust and mantle have been coupled for billions of years, and the presence of a hitherto unknown type of crust in Tibet.
Note 3
The entire account is fictitious and the fact that scientists had any inkling of a positive contribution by it in human physiology only started to emerge almost 90 years later, in the 1980s. The clear link that existed in China between Saltpeter that had to be kept in the mouth for a time and the fact that this “unlocked” healing power was lost to science in the sands of antiquity. Following the 1980s, the physiological importance of nitrate, nitrite and nitric oxide in human physiology became one of the most intensely studied subjects in medicine which lasted well into the 2000s..
A Detailed Survey of Sal ammoniac Production Methods from 1807
Aikin, A., & Aikin, C. R. (1807) writes in their work “A Dictionary of Chemistry and Mineralogy, with an Account of the Processes Employed in Many of the Most Important Chemical Manufactures. To Which Are Added a Description of Chemical Apparatus, and Various Useful Tables of Weights and Measures, Chemical Instruments, &c. &c. Illustrated with Fifteen Engravings.* London: Printed for John and Arthur Arch, Cornhill; and William Phillips.”
“On Sal Ammoniac
Muriate of Ammonia, Salzaures Ammoniak (German). This neutral salt, consisting of muriatic acid and ammonia in a state of mutual saturation, was not unknown to the ancients. In the time of Pliny, it was imported into Europe from Egypt and continued to be furnished by the same country to various states of modern Europe until within the last fifty or sixty years.
It has also been prepared in India, probably in the same manner as in Egypt, from time immemorial. Before discussing the properties of this salt, we shall give an account of its manufacture, first in Egypt and then in various countries of Europe.
Due to the great scarcity of wood in Egypt, the principal fuel of the country is composed of the dung of camels, cows, and other domestic herbivorous quadrupeds, mixed with chopped straw and dried in the sun. The soot produced by the combustion of this fuel is the material from which sal ammoniac is prepared by sublimation. The vessels used on this occasion are very thin globular glass balloons with a short neck terminating in a mouth about one inch in diameter. The largest balloons are about 36 inches across, but they vary greatly in size, being capable of containing, when three-quarters full, from 12 to 50 lbs. of soot. To prevent them from breaking during the process, they are coated with a mixture of mud deposited by the Nile and chopped straw. It has been affirmed by the Jesuit Père Sicard and some others that the soot is mixed with a certain proportion of common salt and camels’ urine, but this appears to be a mistake, contradicted by the most accurate inquirers. From these, it appears that no other ingredient is used but soot, which, moderately pressed down, fills the balloons to within about four fingers’ breadth of the neck. The vessels thus charged are arranged, up to 60 or 70 in number, in an oblong brick furnace and secured with clay so that their necks alone are in contact with the external air. The furnace is now very gradually heated by means of straw for the first three or four hours, and afterward with a mixture of straw and the common fuel of the country, viz. dried dung. In the course of six or seven hours, a thick somewhat acid empyreumatic smoke begins to rise out of the balloons and continues for about fifteen hours. The sublimation of the sal ammoniac commences three or four hours before the smoke ceases, and continues from fifteen to forty hours, depending on the size of the balloon, without any further care being required than to regulate the fire properly and occasionally pass an iron rod down the necks of the balloons to prevent them from being clogged by the rising salt, thus preventing an explosion. When the sublimation ceases, the fire is allowed to go out, and the vessels, as soon as they are sufficiently cool, are removed from the furnace and broken. The cake of sal ammoniac, occupying the upper part of the vessels, is in the form of a very shallow basin and weighs, on average, somewhat more than half the soot employed; it generally has a yellowish-white tinge and is apt to be fouled with a little charcoal, especially if the heat has been too great. The proportion of salt from a given quantity of soot is liable, however, to considerable variation: it is found that the dung of the same animal affords soot much richer in salt when it is fed on fresh vegetables than on hay and other dry food. Moreover, there is a great difference in the soot from the dung of different animals similarly circumstanced as to food: according to Mr. Granger, Egyptian sal ammoniac makers esteem the soot of cow dung when the animal is fed on grass to be by far the best, with 26 lbs. of this yielding no less than 6 lbs. of salt. However, according to Hasselquist, the soot from the dung of goats and sheep is held in the highest regard.
In this very simple manufacture, the sal ammoniac appears to exist ready-formed in the soot, and the action of the heat is confined to merely separating the saline from the other ingredients. The soot itself is of a deep black color, has a taste strongly resembling that of sal ammoniac, and when strongly heated, emits a sulfurous odor. In Europe, where dung is used for better purposes than fuel, the manufacture of sal ammoniac is a much more complicated process, especially when carried out in the best and most economical manner. A kind of intermediate method, however, is practiced with success in some establishments in the Netherlands, of which the following are the principal details.
A kind of fuel capable of producing sal ammoniac by its combustion is first prepared. The ingredients of this fuel are:
- 25 parts by measure of pulverized pit coal
- 5 parts of common chimney soot
- 2 parts of clay
To these is added a saturated solution of common salt in sufficient quantity to bring the whole to a consistency suitable for being molded into balls. The balls are of an oval form and, after being dried in the air, are ready for use.
On the Apparatus for Collecting the Soot
The apparatus for collecting the soot produced by the combustion of this fuel consists of a brick furnace communicating by a flue 2 inches in diameter, with a vaulted chamber, also made of brick. From the opposite extremity of this chamber, a flue of the same diameter as that already mentioned passes out, terminating in a horizontal gallery at the end of which is the chimney. The furnace is charged with the balls mentioned earlier, along with a somewhat variable proportion of dry bones. With these materials, an incessant fire is kept up for from four to six months. At the expiration of this time, the vaulted chamber and gallery are opened, and the soot lining them is scraped off from the top, sides, and floor, taking care to keep the soot from the floor separate from the rest.
The principal new combinations that occur due to the combustion appear to be the following: first, the pit coal is resolved into various gases, empyreumatic oil loaded with finely divided charcoal, and carbonated ammonia. The soot forms carbonic acid and also gives out the carbonated ammonia it contained. The bones afford empyreumatic animal oil and carbonated ammonia. The common salt is decomposed by the action of the clay, its alkaline base remaining united to the earth, and its acid passing in a gaseous state into the chamber, where it meets and decomposes the carbonated ammonia, forming sal ammoniac. Hence, the contents of the soot collected in the chamber are carbonaceous matter, muriate of ammonia, and empyreumatic bituminous oil, the latter of which is particularly abundant in the soot that concretes on the floor.
To separate the sal ammoniac from the other ingredients, sublimation is employed. Several egg-shaped jars, made of earthenware, about 20 inches high and 16 in diameter, with a mouth 2.5 inches wide, are fixed in a furnace. Once they are moderately warm, they are charged with soot broken into small pieces, filling the jars to within three inches of their mouths. A duly regulated heat is then maintained for 48 hours. During this time, the volatile oil first rises and escapes into the air, then the sal ammoniac sublimates and adheres to the upper part of the jars, while the earthy and carbonaceous impurities remain at the bottom. The vessels are then broken, and the cakes of salt extracted. Fifteen pounds of soot yield, on average, about five pounds of muriated ammonia. The soot from the floor of the chamber is too heavily laden with bitumen for the salt to be extracted by simple sublimation. The most economical way to treat it is to burn it again, destroying the bitumen and allowing the sal ammoniac mixed with the soot to rise uninjured into the chamber.
The method of manufacturing this salt in England, though more complicated than the above, is considered considerably more economical. The following was the actual practice at a large establishment near London, which was abandoned a few years ago due to Glauber’s salt being subjected to excise. The material from which the ammonia was extracted was bones. These were collected from the streets and dunghills, mainly by old women. The bones were chopped into small pieces, either by hatchets or machinery, then boiled to extract the grease, fat, and marrow, which was sold to soap-boilers. The bones were then thrown into a cylindrical iron still, about three feet in diameter and eight or nine feet long, laid horizontally over a fireplace, capable of being made moderately red-hot. At one end of the cylinder was a mouth about 14 inches in diameter for introducing the bones, furnished with a cover that could close it accurately with a little lute. From the other end of the cylinder proceeded a cast iron pipe, from six to eight inches in diameter and 18 or 20 feet long, terminating in one or more oblong leaden receivers kept cool by water, placed in a vessel of the same materials. The bottom of this vessel formed their cover, the juncture secured by lute. There were usually two receivers to each still, or three to two stills. Each receiver was about 12 feet long, one foot deep, and 14 inches wide, and the refrigeratory that covered it held about four inches of water. At the end most remote from the still was a pipe fitted with a wooden plug for drawing off the condensed liquor, and above this was a hole through which the gas and incondensible vapor passed into the open air. A single charge of each still yielded about 36 lbs. of impure alkaline liquor and about 30 lbs. of black fetid oil floating on its surface. This latter was skimmed off, and the alkali was saturated with sulfuric acid, either by adding the mother liquor from green vitriol makers (mostly red sulfate of iron) or more economically by calcined and pulverized gypsum. After mixing and stirring the materials, they are left to rest for some hours, during which a double decomposition occurs: the sulfate of lime yields part of its acid to the ammonia, and at the same time deprives this latter of its carbonic acid. The solution of sulfate of ammonia thus produced is then mixed with common salt, causing another decomposition. The alkali of the former and the acid of the latter unite to form muriate of ammonia, while the two remaining ingredients produce, by their combination, sulfate of soda.
Refining Sal Ammoniac
The liquor containing these two salts is then clarified by subsidence and decantation, and transferred into oblong leaden boilers about 9 feet long, 3 feet wide, and 9 inches deep. The boilers are set on iron plates for about half of their length and heated by a fire beneath, with the remaining part supported by flat tiles defended by solid brickwork to keep out the heat.
As the water evaporates, the Glauber’s salt begins to crystallize and is swept from time to time to the cool end of the boiler, from where it is shovelled into baskets arranged over the end of the boiler, so that the liquor which drains from the small granular crystals is not lost. The evaporation continues for several hours until as much as possible of the Glauber’s salt has been separated, and the muriate of ammonia begins to crystallize on the surface of the liquor in the form of feathered stars. The remaining fluid is then run off into coolers and deposits little else than muriate of ammonia until it gets below the temperature of 70°F, at which time the crystals are to be removed, lest they be mixed with Glauber’s salt, which now begins to be deposited again.
After the muriate of ammonia has been allowed to drain in the baskets, it is removed to a kind of oven, or even an open tiled hearth heated from below, where the water of crystallization is driven off, making the salt spongy, friable, and of an ash or slate colour, interspersed with small white filaments. The salt is now removed while hot into globular glass receivers or more commonly glazed earthen jars, fitted with a cover having a hole of about half an inch in diameter in its centre, luted on with a mixture of clay and horse dung. These are set in iron pots over a strong fire, in a furnace of either a circular or oval form, capable of containing from six to eighteen, surrounded with sand up to the edge of the pot, and also having about two and a half inches of sand on the cover, confined by an iron ring about three inches deep and two inches less in diameter than the cover. This setup allows for the luting to be repaired if it gives way without cooling the covers, which should be kept at about 320°F during the sublimation.
These earthen pans may be filled to within two inches of the top with the dried salt gently pressed in, but not rammed close. The fire, which has been lit some time before, is now raised gradually until the iron pots are of a strong red heat all around, being so placed in the furnace that the upper part is first heated, with the bottom resting on solid brickwork. During the first impression of the heat, a portion of the salt carrying with it a quantity of watery vapor not separated in the drying place will escape through the hole in the cover, which must be left open until all the aqueous particles are exhaled. This is known by bringing a piece of cold smooth iron plate near the hole to condense the sublimate, which, becoming more and more dry, eventually attaches itself firmly to the plate in the form of a dry semi-transparent crust.
This time, the hole is to be stopped with a bit of lute, more sand is to be put on the cover, and the heat continued until it is judged that nearly the whole of the muriate of ammonia is sublimed. The time required for this purpose depends on the structure of the furnace, the size of the pots, the briskness of the fire, and other circumstances only to be learned by experience. The process should be stopped before the sublimation has entirely ceased, as the heat in some parts of the jar may be too great when it is nearly empty, and either by burning a part of the salt itself, or elevating a portion of foreign matter from which it can never be kept wholly free, giving the cake a yellow tinge, and a scorched, opaque, crackled appearance. The same defects are likely to happen when any part of the luting gives way and needs to be repaired by wet lute when the sublimation is pretty far advanced. Consequently, glass vessels are preferable, except for the expense, as they must always be broken to pieces to get out the cake; the jars, on the contrary, will serve for several sublimations, even the covers, if well glazed, will last two operations.
The sublimation being finished and the apparatus sufficiently cool, the tops of the jars are to be taken off, and the cakes of sal ammoniac that are found adhering to them are to be separated and placed for a day or two in a damp atmosphere, which softens their surface a little, thus facilitating the removal of any superficial impurities. Lastly, the cakes are packed up in casks for sale.
The following is a table of the proportions of dry carbonate of ammonia afforded by different substances:
- Horn
- Feathers
- Wool
- Soot
- Bones
- Blood
- Putrid urine
In common manufactories, the dry carbonate yields rather less than the sal ammoniac. In most of the Scotch manufactories, soot is used instead of bones, these latter being only abundantly available in the vicinity of a very large town. Muriate of ammonia prepared by any of the above methods possesses the following properties:
It has no smell. To the taste, it is bitter, pungent, and urinous, and at the same time cooling; its colour, when perfectly pure, is a bluish-white; its texture when sublimed is fibrous, tough, moderately elastic, and somewhat ductile, and hence is not easily reducible to powder. Its primitive crystalline form is the regular octahedron, but when crystallized from its solution in water it is either in long tetrahedral pyramids or in flaky feathered crystals; when sublimed it sometimes forms rhomboids, approaching very nearly to the cube; the former crystals are somewhat deliquescent, but the latter, as well as every other sublimed variety of this salt, are permanent in the air.
Specific gravity is 1.42. It is soluble in about thrice its weight of water at ordinary temperature and produces much cold during the solution; boiling water takes up its own weight of this salt, part of which as the solution cools is deposited in beautiful feathery crystals.
When exposed to a dry heat somewhat exceeding that at which lead melts, it begins to rise in the form of a white vapor (without previously entering into fusion) which has a peculiar odor and attaches itself to cool surfaces. It is generally represented as undergoing no change by this process, but according to Beaumé, after repeated sublimations it begins to be decomposed, a little ammonia being first discharged, and afterward some muriatic acid gas.
Muriate of ammonia is decomposable with the abstraction of its acid by the caustic fixed alkalies and by all the alkaline earths, more especially if a moderate heat is applied: the ammonia is volatilized in the form of gas, and the acid remains behind in combination with the added alkali. If a carbonated instead of a pure alkali is employed, and sublimation is had recourse to, the ammonia rises in a mild or carbonated state. Many of the metals and metallic oxides are also capable of decomposing muriate of ammonia in the dry way, ammoniacal gas being disengaged, and the metal remaining behind in the state of muriate. It is remarkable that many metals when thus treated are converted into muriated oxides, although liquid muriatic acid has no effect upon them; thus mercury when triturated accurately with sal ammoniac and heated, disengages ammoniacal gas, and muriated mercury is the result. If, however, an excess of ammoniacal muriate is present, this excess combines with the muriate of mercury, forming the sal-alembroth, as mentioned under the article MERCURY. Silver by similar treatment decomposes sal ammoniac and is itself converted into luna cornea.
Sulfuric acid is capable of decomposing muriate of ammonia by distillation, the muriatic acid being volatilized and sulfate of ammonia remaining in the retort. Nitric acid and muriate of ammonia react upon each other; the muriatic acid is liberated from its base by part of the nitric acid, while another portion of the same is decomposed, and its oxygen passes to the muriatic acid, thus converting it into the oxymuriatic. Hence, the old chemists were in the habit of composing an aqua regia by dissolving sal ammoniac in nitrous acid for dissolving gold; the occasional bad consequences of which were mentioned when treating of that metal. The action of nitre and sal ammoniac in solution has not been investigated; but if the latter salt is added to nitre in fusion a partial deflagration takes place, no doubt in consequence of the mutual decomposition of the ammonia and nitric acid. According to Gellert, a boiling hot solution of muriate of ammonia is capable of dissolving vegetable resin. The action of sulfur and sal ammoniac on each other has been scarcely examined. Pott affirms that if one part of the former and two of the latter are sublimed together, the inflammability of the sulfur is destroyed. The water of composition contained in sal ammoniac is the same in quantity according to Beaumé, whether the salt is sublimed or crystallized from its aqueous solution. Mr. Kirwan agrees with this, who states the component parts of sal ammoniac, whether sublimed or crystallized, as:
- 42.75 Muriatic acid
- 25.00 Ammonia
- 32.25 Water
- 100.00
The uses of sal ammoniac are considerable. Besides being employed in the laboratory as the substance from which pure and carbonated ammonia is procured, it is used in substance by the dyer, the refiner of gold, the coppersmith, and the manufacturer of tin plate.”
-> Evaluation
It seems that any part of the animal was used to create sal ammoniac.
- Horn
- Feathers
- Wool
- Soot
- Bones
- Blood
- Putrid urine
An interesting observation from The New York Tribune quote of 31 January 1874 the dung of four-footed animals that feed only on vegetables “is fit to burn for sal ammoniac only during the four first months of the year when they feed on fresh spring grass, which, in Egypt is a kind of trefoil or clover; for when they feed only on dry meat, it will not do. The dung of oxen, buffalo, sheep, goats, horses, and asses, are at the proper time as fit as the dung of camels for this purpose; it is said that even human dung is equal to any other.” In other words, sal ammoniac (ammonium chloride) production from animal dung is influenced by the diet of the animals. Specifically, the quality and quantity of sal ammoniac produced are better when the animals consume fresh, green vegetation compared to dry fodder.”
This being true, if the dung from geese would be used who feed on green vegetation such as grass, it would make their dung a potentially superior source for producing sal ammoniac. Given their diet, it stands to reason that goose dung would be rich in the necessary components that, when burnt, produce high-quality sal ammoniac.
The only possible explanation I have for this is that fresh vegetation likely contributes to higher nitrogen content and other favourable chemical properties that facilitate better sublimation of sal ammoniac.
References
All the “Further Reading” articles are my references.
Bacon Curing – A Historical Review
Photo References
Domingos, S. S.. (2011) Vertical flow constructed wetlands for the treatment of inorganic industrial wastewater. Murdoch University WA, Australia.
Featured Image: Bezeklik caves on mountain slopes near Turfan. https://www.advantour.com/china/turpan/bezeklik-caves.htm
Flaming Mountains of Turfan: https://za.pinterest.com/pin/334251603567115799/?lp=true
McCulloch, John Ramsy. (1845) M’Culloch’s Universal Gazetteer: A Dictionary, Geographical, Statistical, and Historical, of the Various Countries, Places, and Principal Natural Objects in the World.
Turfan Depression: http://www.howderfamily.com/blog/turpan-depression/