*** article being written – incomplete notes ****
THE SILK ROAD
The location of the Turpan-Hami and Tarim Basins are very important. Crossing the Taklimakan Desert is possible at the foot of the mountains surrounding the Turpan-Hami Basin or along its streams such as the Tarim, “that spring from the mountains to enter the desert from its periphery but soon vanish into the sand. As ancient caravans from Eastern China approached Dunhuang at the edge of this segment of what eventually came to be part of the Silk Road to the Medditeranian, the near absence of water in the desert’s centre forced them to make a choice. The southern option skirts the desert along its southern edge at the foot of the steep Kunlun slopes descending from Tibet’s high plateau. Alternatively, the northern route passes through Hami and those communities living along the Kongi and Tarim rivers that lead to Loulan and Lop Nor. It is along these routes that mummies from the Tarim Basin have been found.” (Aufderheide, A. C.; 2003: 268, 269)
The caravans on the silk road approached Dunhuang, crossing vast sodium and potassium nitrate deposits. If the knwoledge of its power was developed in this region and exported to Europe, I am sure that there should be remnants of this ancient knowledge in this city.
“One of the people who has extensively studied the Caucasian mummies of China, Professor Victor Mair of Pennsylvania University, said that he believes that early Europeans long ago spread out in different directions. He believes that some of these peoples traveled west to become the Celts in Britain and Ireland, others went north to become the Germanic tribes, and still others journeyed east to find their way to Xinjiang. These ancient European settlers are believed to represent some of the earliest human inhabitants of the Tarim Basin, and Mair has stated that from around 1800BCE the earliest mummies to be found here are exclusively Caucausoid or Europoid rather than Chinese in origin.” http://mysteriousuniverse.org/2014/10/the-mysterious-european-mummies-of-china/
The chemistry of alkaline C in desert sands
The Atacama link would mean that this was far more widespread than even thought by the two researchers and, depending on their particular proof, we know that preservation with either sodium or potassium nitrate salts were practised in Peru, Chili and China. It would make it completely reasonable to assume that this would have been the case in India also where vast natural deposits of potassium nitrate are found.
I thought that the reddening effect would have been the first reason to use nitrate and to distinguish it from other meat because it is so visual and obvious. If I had to guess, I would have said that the preserving power of nitrate and nitrite would have been a later discovery, but even from the comments of Binkerd and Kolari, and conjecture based on the mummification practices in Chili and Peru, it would now appear to me that the colour concerns were secondary and the primary reason for using these salts was due to their preservation and anti-microbial character.
The general climatic requirement of Binkerd and Kolari’s “saline deserts” and “coastal areas” is applied in “The Meat we Eat” by Romans et al., (2001) to suggest the origins of general salt curing of meat to have originated with the Sumerian culture, which emerged in the Tigris and Euphrates valleys, approximately 4,000 BC. Here we have a date, but how did they come up with it? I will return to the use of sodium chloride for preservation in this region later.
migration along the silk road
general on salt
Nature of the salts in China
Aeolian Carbon Salts in the Taklamakan and Badanjilin Deserts in Northwestern China and Their Potential Role in Global Carbon Cycle http://article.sciencepublishinggroup.com/html/10.11648.j.aos.20170201.15.html
benefits on NO and the advanced nature of chinese views on nitrate
https://books.google.co.za/books?id=OgusGV1EKA0C&pg=PA156&lpg=PA156&dq=Dunhuang,+meat+curing&source=bl&ots=eBJY7xO6Zc&sig=FxMGY9JsM5OTLGZQfccVk2MfZdg&hl=en&sa=X&ved=0ahUKEwidyp3u9JDUAhWkOsAKHXVnCjYQ6AEITzAJ#v=onepage&q=nitrate&f=false (excellent on Dunhuang menuscripts)
mummies in general
Human body preservation – old and new techniques https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931544/
deserts and saline lakes
Europe – salt
oldest examples of salt preservation
Early Arabic Pharmacology: An Introduction Based on Ancient and Medieval Sources https://books.google.co.za/books?id=LtYUAAAAIAAJ&pg=PA7&lpg=PA7&dq=Sumerian,+%22nitre%22&source=bl&ots=4IvSEchl1E&sig=o7sgBYPp9fwwUAER1EVUPUID9Tw&hl=en&sa=X&ved=0ahUKEwjqu_38wIHUAhWFCcAKHddYDjIQ6AEIJjAC#v=onepage&q=Sumerian%2C%20%22nitre%22&f=false
Evidence for Prehistoric Origins of Egyptian Mummification in Late Neolithic Burials http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103608
Organic chemistry of balms used in the preparation of pharaonic meat mummies http://www.pnas.org/content/110/51/20392.abstract
The Sumerians: Their History, Culture, and Character https://books.google.co.za/books?id=IuxIdug8DBUC&printsec=frontcover&dq=Sumerian+culture,+Tigris+and+Euphrates,+4,000+BC,+salt,+meat&hl=en&sa=X&ved=0ahUKEwjfmOK6vYHUAhXEAMAKHcWgC1MQ6AEIPTAF#v=onepage&q=meat&f=false
the history of energy and early man in europe
alternatives for curing
Now, returning to the line of inquiry that follows the practice of embalming. It continues to reveal some surprising. The earliest evidence we have of embalming in Egypt dates back to around 5000 BCE. (Wohl, V) The mummies from this period talk to us in an epoch well before writing was invented. The oldest surviving text from Egyp dates back to around 34oo BCE. She writes, “Our knowledge of the process comes primarily from descriptions written about 500 BCE by the famous Greek historian, Herodotus. Nearly 500 years later, in 45 BCE, Siculus, another historian, would write about the process.” From this, it is clear that even though the words date from between 500 and 45 BCE, the traditions that it chronicles may be between 4500 and 500 years older. It is impossible to say unless we examine the actual mummies.
Lets first look at what is recorded in the words of Siculus and Herodotus. They reveal that in cases of “evisceration, all the viscera except the kidneys and heart were removed and cleansed, then immersed in a container of palm wine and packed in natron.” The entire body was then “immersed in a high concentration of natron for 20 days. After that, it was rinsed with water and dried in the sun.” “Egyptologists use the term natron to refer to a variety of chemical compounds; specifically, sodium chloride (table salt), sodium carbonate (Na2CO3 or soda ash), sodium bicarbonate (NaHCO3) and sodium sulphate (Na2SO4).” (Bertman, S.. 2010)
In Europe, there is a description of an embalming process from around the 500’s AD from the writings of contemporary physicians, Peter Forestus (1522–1597) and Ambroise Paré (1510–1590) where amongst other, a washing solution of salt is used. The salt was part of Paré’s list. Forestus’s list contains another very interesting ingredient in rosemary which is such an excellent natural antioxidant that it is used in natural curing brines to this day.
During the middle ages, it became important to preserve bodies for research. Leonardo da Vinci (1452–1519) described a method of preserving the cadavers for his own research. (Brenner, E.; 2014) The mixture he used consisted of turpentine, camphor (scent masking), oil of lavender (scent masking), vermilion (colouring agent), wine, rosin (a resin used as an adhesive), sodium nitrate, and potassium nitrate. In his mix, for preservation, he relied on sodium and potassium nitrate and turpentine. This means that not only did cultures from around the world understand that there is a meat preserving power in saltpeter, possibly from as early as 5000 BCE, but in the 1500’s, saltpeter is a known agent to preserve meat.
Amongst certain cultures technology was then developed, for various reasons, to preserve meat through adding salt. Why and how this happened is a matter of great fascination and I will dedicate much time to this question over the years to come.
What is clear is that as our way of life became more sophisticated, we domesticated our food sources and salt played an ever increasing role in importance in our interaction with domesticated animals and preparing food. The first food source that we domesticated was the wild fig, probably many years before we did the same to grain. Archaeologists found domesticated figs dating back to 9400 BCE. Sheep were domesticated around 8000 BCE, cattle, and pigs around 7000 BCE. (Bitterman, M, 2010: 17)
In general, we can say that sometime between 15 000 and 5000 BCE, human society’s use of salt increased rapidly as salt became popular for use in our own food and for our domesticated livestock. Food for livestock was supplement with salt and we expanded its utility to curing and preserving foods, tanning hides, producing dyes and other chemicals and for medicine. Humans “evolved with a physiological requirement for salt; our culture was born from it. Access to salt became essential to survive. Salt localised groups of people.” (Bitterman, M, 2010: 17) Curing took meat which we culled from nature and brought it into culture. (Laszlo, P, 1998: 14) It turned the art of preserving into an expression of community and “togetherness” by transforming “preservation of food” into culinary delights of great enjoyment. Salt not only have great functional benefits but also improves our experience of taste.
Salting made it possible to trade in perishable foods. There is evidence that by 1,200 BCE, another great traders civilisation of ages past, the Phoenicians, were trading salted fish in the Eastern Mediterranean region. (Binkerd, E. F.; Kolari, O. E. 1975: 655–661) Saltworks were one of the main features of their settlements in Lebanon, Tunisia, Egypt, Turkey, Cyprus, Crete and Sicily.
By 900 BCE, salt was being produced in ‘salt gardens’ in Greece and dry salt curing and smoking of meat were practised and documented. (Binkerd, E. F.; Kolari, O. E. 1975: 655–661) Ancient records of 200 BCE tell us that the Romans learned how to cure meat from the Greeks and further developed methods to “pickle” various kinds of meats in a brine marinade. Salting had the effect of reddening the meat and the report of this observation became the first recorded record of the colour effect of saltpeter. (Binkerd, E. F.; Kolari, O. E. 1975: 655–661) By this time, saltpeter and sea salt were two salts that were identified early on.
Through the centuries, adding salt to meat (2) evolved into an art. The spread of culinary practices, including the use of salt, and the development of these into an art form was spread as humans interacted with neighbours and ventured out to establish trading stations and colonies. Greece, for example, was influenced by the eastern kingdoms of Lydia and Persia. From the west, it was influenced by its own colonies established early in the 8th and 7th centuries BCE. One of these colonies was on the island of Cicily. (Freedman, P. H.; 2007: 78)
It was here, in Sicily, where European cuisine as an art form was born by the ingenuity of local cooks. (Freedman, P. H.; 2007: 78) Salt was one of the world-famous industries of Sicily and the finest salt is still available from the island today. The functional value of saltpeter in meat curing was well established by the 1800’s and universally used, but some of the most famous meat dishes have been made with fresh produce, good quality meat, and simply cooked, in many instances, with salt only.
Mid-way through the 4th century BCE, Archestratos, a Greek poet from Sicily, wrote the “Life of Luxury” which is advice to the reader on where to find the best food in the Mediterranean world and how to prepare it. He gives, for example, advice on the preparation of a favourite fish from the region, gray mullet. Readers are advised to buy the best fish they can, in this case, from Miletus. Roast it whole in glowing hot coals, wrapped in fig leaves only – take care not to over-cook it – and sprinkle it with salt only. (Freedman, P. H.; 2007: 80)
Another example of a simple recipe with salt is from the writings of Marcus Porcius Cato (234 BCE – 149 BCE) or Cato the Elder who was a Roman statesman who devoted himself to agriculture when he was not engaged in military service. He recorded careful instructions in dry curing of hams. (Hui, YH, et al, 2001: 505) In his Latin work, De Agricultura (On Farming), written in 160 BCE, this Roman statesman, and farmer, gives an ancient recipe for curing pork with salt.
“After buying legs of pork, cut off the `feet. One-half peck ground Roman salt per ham. Spread the salt in the base of a vat or jar, then place a ham with the skin facing downwards. Cover completely with salt. After standing in salt for five days, take all hams out with the salt. Put those that were above below, and so rearrange and replace. After a total of 12 days take out the hams, clean off the salt and hang in the fresh air for two days. On the third day take down, rub all over with oil, hang in smoke for two days…take down, rub all over with a mixture of oil and vinegar and hang in the meat store. Neither moths nor worms will attack it.” (economist.com)
Cato may have imitated a process whereby hams are smoked over juniper and beech wood. The process was probably imported by the Roman gourmets from Germania. (economist.com) This is an important clue of the region where our salt -cured and wood smoked bacon originated from.
The use of salt and understanding its production developed hand in hand. Phoenician ships spread the technology of salt making across the Atlantic, to Spain and as far north as England. India, China, Japan, and Africa developed their own salt industries. Salt was used globally and hardly a region on earth or a civilisation could be found who did not produce it. Salt was taxed, traded, used as currency and consumed on a global scale. (Bitterman, M, 2010: 17 – 25)
In South Africa, one such ancient salt mining site is found at ………
WHAT IS A SALT
Humans noticed that not all salts were the same. Simple observation through taste and visual evaluation made us aware of differences in salt from different locations and regions. Some salts seemed to have almost magical properties. It is our desire to understand these differences that directly lead to the establishment of the science of chemistry. Unravelling the character of salt is one of the greatest stories that exist.
Today we know that a salt is formed when an acid and a base are combined through what is called a neutralisation reaction. The crystal or in many cases, polycrystal are ionic compounds, meaning that it is a rigid and regular arrangement of particles of opposing electric charge. The particles are “glued” together by strong ionic or less strong, electrostatic bonds.
This simple explanation did not come easily and unraveling the mystery of the composition of salt took many years and the dedicated work of some of the most brilliant and often, eccentric people who ever walked this earth in recent years. Simple observations of the reaction of different salts in combination with various compounds and understanding their characteristics such as taste was the first step. Soon, though, simple observations were not enough and a comprehensive system had to be built in order to take the analysis further. It took many years and the labour of many to developed a theoretical understanding of the nature of matter and the forces that hold it together and govern its reactions. Today we know this system as the scientific discipline of “chemistry.” In the process, often, understanding had to wait for the foundations of science itself to be developed before real progress became possible. In the end, incremental as it was and over many generations, insight developed to the point where we could claim the basic understanding of the nature, composition, and function of salts.
Early on, different salts that were known included sea salt, rock salt, saltpeter and tartar. Clues to their identification come to us in writings and in drawings.
Below is the woodcut of the “Man Collecting Tartar From an Empty Wine Barrel, taken from Ortus Sanitatis, a book published in Strasbourg in 1497. The man is “collecting precipitated solids (potassium hydrogen tartrate) from a wine barrel for use in making potash (potassium carbonate). The solids, known as wine lees, argol or tartar, are formed during wine fermentation. When the argol is heated it forms potash. Potash is used in the manufacture of soap and glass.”
THE PRINCIPLES OF PARACELSUS
Unravelling the identity and composition of salt gained momentum with the work is the multi-talented physician, Paracelsus (1493 – 1541), who saw salt as one of the three principles namely salt, sulfur, and mercury. This contemporary of Copernicus, Leonardo da Vinci and Martin Luther, widely regarded as the founder of toxicology, imagined that in every object the principle responsible for its solid state is salt; a second principle (sulfur) is responsible for its inflammability or “fatty” state; and a third (mercury) is responsible for its smoky (vaporous) or fluid state. (www.scs.illinois.edu)
A “fire analysis” was done on a body to isolate the salt. Many cultures, across the world, developed the concept which in the West became popular by the teachings of Empedocle (c. 490 – c. 430 BCE) that all matter comprises of earth, air, fire, and water. Earth being the passive element which remains after the fire analysis. By the late 16th and early 17th century, it was realized that the solid which remained after the fire analysis, could further be divided into SALT, which could be removed by diluting it in water and what remained was called EARTH. EARTH was the non-volatile residue left after burning and SALT diluted in water and had a saline taste. While Luther’s reformation was transforming church life across Europe and Da Vinci was painting the Last Supper in the Convent of Santa Maria delle Grazie, in the city of Milan, Paracelsus taught that salt, thus extracted, demonstrated the presence of the universal salt principle and that it was this principle that was behind any body’s solid state and its resistance to fire. The criteria for SALT being that it is able to be diluted by water and have a saline taste is the reason why liquid acids also came to be known as salts. (Siegfried, R.; 2002: 76, 80, 81)
One of the most colourful individuals who materially contributed to our early understanding of salt was the Bavarian alchemist and chemist, Johann Glauber (1604 – 1670) who reported in the mid-1600’s on the mutual destruction of acids and alkali’s. Hailing from a poor background, he traveled and learn alchemy from various laboratories and teachers. At age 20 he was afflicted with stomach problems, probably after contracting spotted typhus which, for some time after contracting it, causes nausea and vomiting. His travels across Europe brought him to the city of Vienna where the residents recommended that he drinks from a local miracle spring which will restore him to health again. Glauber was skeptical about the idea but did it in any event. He drank from “Hungarian Spring.” (5) His appetite returned and soon he was in good health again. (www.thechemicalengineer.com and Siegfried, R.; 2002: 77)
This unlikely outcome pricked his curiosity. Locals believed the healing power to be due to the presence of saltpeter in the water. He spent the winter, evaporating water from the spring and analyzing the salt. What he found was not saltpeter, but sodium sulfate. (www.thechemicalengineer.com) Sodium sulfate is a mild laxative and he would later market it as Glauber’s salt. The study of niter would preoccupy him for years to come, but in his mid-fifties, sodium sulfate would take front and center stage in his research work. He got carried away when naming it “Sal Mirabilis Glauberi.” He overstated its healing power so dramatically that he received considerable opposition from his contemporaries who regarded him as a dreamer and charlatan. (The Guardian, 1934) An interesting fact to note for our continued interest in the study of saltpeter is the ease with which he was able to test for saltpeter by the mid-1600s. He was able to produce nitric acid (HNO3) by applying sulfuric acid to saltpeter. Later he made potassium carbonate (K2CO3, which is produced by burning saltperter with charcoal) and nitric acid (HNO3) which they made by distilling satlpeter with fullers earth) from saltpeter and was able to combine these two, potassium carbonate and nitric acid to yield saltpeter, showing his thorough grasp of the acid-base composition of salts. (www.encyclopedia.com) Nitric acid or spirit of niter is a volatile acid and fixed niter (potassium carbonate) is a solid caustic. From this, Glauber concluded that twofold substance, containing both and acid and an alkali.
It was the fact that he could reconstitute saltpeter with fixed potassium carbonate and nitric acid that showed him that saltpeter was not the ultimate universal solvent which alchemists were looking for and that he claimed to have found. It was this disillusionment with niter that caused him to turn his attention back to his Sal Mirabilis Glauberi or sodium sulfate. The formulation of Glaubers salt is Na2SO4·10H2O.
Glauber’s contribution to the study of salts was considerable. He eventually expanded the list of known salts far beyond common salt and niter. His work on the mutual destruction of acids and alkali’s was done with Otto Tachenius. (The Age, 1975)
Glauber introduced the idea that acids could combine with metals or alkali’s to form a salt. The mechanism behind the combinations is seen by him as a certain associative principle which he called “Gemeinschaft.” In his work, he insisted on an accurate description of the technical operation at work. (todayinsci.com) (6)
THE ACID-ALKALI REACTION OF SALTS
The medical chemist, Van Helmont, created a model in the 1600’s and he postulated that this acid-alkali reaction is part of animal digestion. One of his students by the name of Sylvius, progressed this idea and thought of all bodily functions as acid-alkali reactions and bodily fluids are either acid or alkali. (Siegfried, R.; 2002: 76) Robert Boyle (1627 – 1691) refuted this suggestion by showing some of the many exceptions, yet the reaction between acids and alkali remained “the most familiar among real laboratory material.” By the end of the 1600’s, there were three well-known mineral acids, namely, spirit of niter (nitric acid), spirit of salt (hydrochloric acid), and vitriolic acid or spirit of sulphur (sulfuric acid). (Siegfried, R.; 2002: 77)
When exactly the acid-alkali reaction was first studied or who identified it has not been uncovered. It is one of the great untold stories of science. What we know is that during the 1600’s, the term alkali was first used in the Arab world and referred to a vegetable alkali. Books from that time refer to a plant that was called kali and contained potassium carbonate. The ancients obtained it from leaching ashes from the burned remains of the plant. (Siegfried, R.; 2002: 77)
By the 1600’s, they recognized another common alkali namely alkali of tartar. This was obtained from the residue in wine barrels and today we know that it was also potassium carbonate. In the early days, they retained the particular name to link it to where it was found. (Siegfried, R.; 2002: 77)
The saturation point of an acid-alkali reaction was believed to be the point where the effervescence stops. At this time, air was not a recognized chemical element and nobody had the idea that the effervescence could be due to the liberation of air. Robert Boyle developed an alternative way to test for acidity or alkalinity and to determine the saturation point of acid-alkali reactions. In his time it was already well known that acids turn green vegetable colour, red. Boyle was probably the first to observe that an alkali would turn the blue to green. It took until 1750 before the use of colours to identify acids and alkali’s became commonplace in the scientific community. (Siegfried, R.; 2002: 77)
By the beginning of the 1700’s, a third class of salts was well established namely neutral salts, containing both acid and alkali. These salts did not effervesce with either acids or alkalies. This category was soon expanded to include the combination of an “acid with earths and metals as well as with alkalies.” (Siegfried, R.; 2002: 77)
Earth is what remains at the end in a distillation vessel and can not be dissolved in water. There has been a debate whether different earths exist as was the case with different salts and sulfurs (or oils). Scientists were able to, for example, identify a certain kind of earth derived from stones, coral or seashell. It is able to dissolve in acid and when strongly heated, it forms a powdery residue that absorbs water. These were known as absorbent earths. (Heilbron, J. L.; 2003: 226)
The great French chemist, Guillaume- François Rouelle (1703-1770), under whom Lavoisier studied, published some of his most important work between 1744 and 1754 on the subject of salt. At this time, salt was defined as water-soluble, saline-tasting solid. He suggested what is essentially the modern understanding of salt (sel). He was the first to distinguish between acid, neutral, and basic salts. That is, anything that would fix the acid into a solid state whether an alkali, an earth or a metal. (Siegfried, R.; 2002: 79)
Another scientist of this time who devoted much of effort to the study of neutral salts was the German scientist, Wilhelm Homberg (1652 – 1713). He spent his adult career in Paris. By the time of his most important work, the neutralization of an acid by and alkali and the mutual destruction of properties was well established during the previous century. “The available salts were the vitriolic or spirit of sulphur, spirit of niter, spirit of sea salt, and acid of vinegar. The only alkali was salt of tartar (potassium carbonate). ” (Siegfried, R.; 2002: 86)
From the wok of Homberg, it is clear that the implicit principle behind his experimental work was the conservation of weight. An example is an experiment he did in 1699 where he set out to determine the amount of volatile acid salts contained in its solution. “He added acid to weight quantity of alkali until the alkali was saturated, presumably judging that point by the cessation of effervescence. The resultant salt was then dried as thoroughly as possible and weighed. The increase in weight Homburg took to be the weight of the real acid in the solution used. He carried out this procedure using spirit of niter, oil of vitriol, aqua regia, and distilled vinegar, compiling tables of his results. He took no account of the loss of carbon dioxide that escaped from the alkali, of course, for he knew nothing of it.” We see “how futile these attempts were until glasses were recognized as part of chemistry and techniques were developed for measuring and isolating the different kinds of air.” (Siegfried, R.; 2002: 88)
It was about this time when the analysis/synthesis cycle was established as a way to confirm the qualitative composition of a body. If elements obtained from an analysis by fire could be reformed again into the original body, it would prove that the analysis was done correctly and the elements that constitute it, identified. “The permanent secretary of the Academy (of science in France), whose duties included the writing of summaries of the worthy articles in the Mémoires commented that “One is never so sure of having decomposed a mix into its true principles as when with the same principles one can recompose it.”” (Siegfried, R.; 2002: 90)
SALTS KNOWN IN THE 1700’S
Before the 1700’s, scientists could not distinguish between the different alkali metals. Sodium and potassium were often confused. Potassium was produced artificially by slowly pouring water over wood ashes and then drying the crystal deposits. Some of these metals were also found naturally on the edges of dried lake beds and mines and sometimes at the surface of the ground.
At the beginning of the 1700’s, only a few salts were known namely vitrios, alum, saltpeter and borax. In 1703 Nicholas Lemery showed it is a neutral salt by not showing any fermentation when treated with different alkali salts and various acids. Sodium as the alkali in borax (sodium tetraborate) was identified shortly thereafter, but the acid was identified only early in the 1800’s.
Henri-Louis Duhamel (1700 – 1782) realised that certain metals had similar characteristics. He studied samples of salts found in nature and produced by people artificially. This included the study of saltpetre (potassium nitrite), table salt, Glauber’s salt, sea salt and borax. (Krebs, RE, 2006: 51) He discovered sodium carbonate and hydrochloric acid, a solution with a salty taste, in 1736. (Brian Clegg, rsc, chemistryworld)
ANTOINE LAURENT LAVOISIER
It would be the work of Antoine Laurent Lavoisier that finally establishes chemistry into a science. He did for chemistry, what Newton did for mechanics 100 years earlier. Lavoisier did not discover any new substance, nor did he build any new laboratory- or investigative device. What he brilliantly did was to take the known facts and from these, gleaned the right interpretations. Acids and bases have been examined systematically, chemical substances have been described and characterized, and much work has been done on the relative affinity of bodies for one another.
About saltpeter, Lavoisier concluded that “nitrous and nitric acids are produced from a neutral salt long known in the arts under the name saltpeter.” He explains that this salt is extracted through the process of leaching from the “earth of cellars, stables, or barns, and in general of all inhabited places.” In these places, the reaction of nitric acid takes place with various basis such as lime, magnesia (magnesium oxide; magnesium reacts with nitric acid to give magnesium nitrate and hydrogen gas), potash or argill. (Lavoisier, A; 1965: 214)
Then, at the dawn of the 19th century, an unusually gifted young, English scientist burst onto the scene, Humphry Davy. It was this uniquely talented young man who changed history when he isolated sodium and potassium in 1807.
He had the first direct electric current generator at his disposal, the electric battery that Alessandro Volta had invented in Paris in 1800. Davy ran an electric current through caustic soda (sodium hydroxide) and was able to isolate sodium from it. He did the same for potassium, isolating it from potash.
Chlorine was already being produced through electrolysis by the decomposition of sea salt by the electric current. Caustic Soda and chlorine had many applications by the end of the 1700’s.
Fats were processed with caustic soda to produce soap. Fabrics were being bleached with chlorine, a process discovered by Berthollet. (Laszlo, P, 1998: 50)
In 1807, Humphry Davy found that the “muriate of soda” produced by burning sodium in a vessel full of chlorine was chemically identical to salt. (Brian Clegg, rsc, chemistryworld)
Humphry wrote in 1840, “Sodium has a much stronger attraction for chlorine than oxygen; and soda or hydrate of soda is decomposed by chlorine, oxygen being expelled from the first, and oxygen and water from the second.”
“Potassium has a stronger attraction for chlorine than sodium has; and one mode of procuring sodium easily, is by heating together to redness common salt and potassium. The compound of sodium and chloride has been called muriate of soda, in the French nomenclature; for it was falsely supposed to be composed of muriatic acid and soda; and it is a curious circumstance that the progress of discovery should have shewn that it is a less compounded body than hydrate of soda, which 6 years ago was considered as a simple substance, and one of its elements. According to the nomenclature which I have ventured to propose, the chemical name for common salt will be sodane.”
“Common salt consists of one proportion of sodium, 88, and two of chlorine 134; and the number representing it is 222” (Davy, H. 1840: 247)
The importance of this is that the knowledge that the salt used for preserving food is mainly sodium chloride, existed from the early 1800’s.
It was now possible to analyse the nature of sodium chloride and the other kind of salts that exist. The nature of the composition of salt that has been dissolved in water and the interaction between salt and meat and between salt and microorganisms such as bacteria that are present in meat.
It is possible to look at everything that makes up sea salt and salt from inland springs and dry salt beds and we can begin to understand and appreciate the effect of salting meat and how it happens that it preserves the meat. It was found that salt had other metals and compounds of a diverse, but consistent nature. These other elements present in salt that we find naturally on earth, do they impact on the curing process at all? And if so, how? (4)
SALT AND WATER
Let us consider the effects of salt and water on melting of ice. We do this because we want to understand the chemistry of thawing frozen meat in water.
The background on salt, water and how ice responds to this comes, courtesy of Melanie Shebel who writes that “we know that melting or freezing is an equilibrium process. The energy that is required to melt ice will not contribute in elevating its temperature until all the solid water is molten.”
“If we take two ice cubes and add salt to it, then put each of them at room temperature, both of the ice cubes will absorb energy from the surroundings, and this energy as we said, will contribute in breaking down the bonds between water molecules.”
“The cube that has not salt been added to, has a melting point 0 deg C and so if we measure its temperature during melting it will remain zero until all ice is molten. That ice cube to which we have added salt, the salt that is added lowers the melting and freezing points of water because it lowers the vapor pressure of water. This ice cube will absorb energy from the environment to help break bonds between water molecules. We know that the salt added will dissolve in the melted portion of the ice. This formed solution of salt will have a lowered freezing point, so the equilibrium between the solid phase and the aqueous phase will be shifted towards the liquid phase since such a solution will freeze at say −2 deg C. Since both phases are close together, the ice will absorb energy from the salt solution and will reduce its temperature to the −2 deg C to maintain the equilibrium. When all ice is molten we end up with a salt solution that has got a temperature of say −1.5 deg C. This is due to the solution being diluted now. After that, it will start absorbing heat from the room and reach zero and above.”
“When you dissolve NaCl in water, it will have to take energy from the system to break its structure so it can dissolve in water. This is the reason the water gets colder because the salt uses the energy from the water to solve it. Now let’s look again at why ice melts when salt is added. This is based on a so-called colligative attribute. These attributes are only dependent on the amount of substance. When you add particles to a solvent, its vapor pressure lowers. This will result in a higher boiling point(using salt for cooking) and a lower freezing temperature for the solution.”
(c) eben van tonder
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(1) We have seen how pervasive the occurrence of nitrate is on earth. One expect to find it in every natural salt spring, salt marsh, dry salt lake and in sea water. “Some curing” will take place with almost any natural salt. However, it has been shown that bacon that was produced with either no nitrites or nitrite levels of 15 ppm, “off-flavours were high and increase rapidly. A significant reduction in off-flavours in pork during storage was observed when nitrites were added > 50 ppm.” (Rahman, SM, 2007: 307)
Salt springs, analysed in South Africa contained as little as < 1 mg/ L of Nitrate (H)
This does not correlate with the statement by Smith and the American Encyclopedia about the fact that normal salt was equally successful in curing meat.
Adding salt enhance the flavour, but it also accelerate lipid oxidation, even at low levels of addition. Lipid oxidation leads to off flavour development in meat that does not contain any nitrites. Even a 0.5% addition of sodium chloride significantly increase lipid oxidation when added to restructured pork chops and pork sausage patties following freezer storage. (Pearson, AM, et al, 1997: 269)
(2) Bent Sørensen is professor emeritus at Roskilde University (Denmark), He has held academic positions at University of California in Berkeley, Yale University,The National Renewable Energy Laboratory in Golden (US), Kyoto University (Japan), University of Grenoble (France), Niels Bohr Institute at Copenhagen University (Denmark) and University of New South Wales (Australia). He has served as advisor for the OECD, the Japanese and Australian governments, and various UN agencies, as technical director and board member of Novator and Cowi Inc., and as lead author for the IPCC working group on climate change mitigation. He served as chairman of the Danish Energy Agency Solar Energy Committee and the Hydrogen Energy Committee, and received prizes such as the Australian-European Award for Eminent Scholars (1982) and the European Solar Prize (2002). In 1989, he was knighted by HRH Queen Margrethe of Denmark. He is the author of some 25 books and nearly 1000 articles, most of which in peer-reviewed journals, and covering a cross-disciplinary range of fields, from physics, mathematics and engineering to economy, environmental science, philosophy, political science, history and archaeology.
(2) ‘The binomial name Homo neanderthalensis – extending the name “Neanderthal man” from the individual type specimen to the entire species – was first proposed by the Anglo-Irish geologist William King in 1864 and this had priority over the proposal put forward in 1866 by Ernst Haeckel, Homo stupidus. The practice of referring to “the Neanderthals” and “a Neanderthal” emerged in the popular literature of the 1920.” (Wikipedia. Neanderthal)
(3). Meat curing can be defined as the addition of salt to meat for the purpose of preservation. (Hui, YH, et al, 2001: 505)
(4) It turns out that “food-grade salt of the highest purity should be used in meat curing practices. Impurities such as metals (copper, iron, and chromium) found in natural salt beds, salt produced from salt springs or sea salt accelerate the development of lipid oxidation and concomitant rancidity in cured meats. Although salt may be of very high purity, it nonetheless contributes to meat lipid oxidation. Nitrite and phosphates, help retard this effect.” (Hui, YH, Wai-Kit Nip, Rogers, R. 2001: 492)
(5) One source says that this took place in Naples and not Vienna. There could have been been a spring in Naples, called Hungarian Spring. Drug Discovery: A History by Walter Sneader, 2005, John Wiley and Sons Ltd., p. 64 puts the place where he became ill as Vienna, which fits the Hungarian Spring designation much better.
(6) There is at least one source that puts his invention of Glaubers salt at 1659. However, from The Renaissance of Science: The Story of the Cell and Biology, by Albert Martini, 2015, Abbott Communications Group, Glauber discovered a simple method of manufacturing hydrocloric acid in 1625, when he was 21. He did this by combining sulfuric acid with table salt (sodium chloride). Sodium sulfate salt was produced by this reaction which is Glauber’s salt, a mild laxative. On the other hand, the 1659 date for the invention of Glaubers salt may refer to the publication in 1658 of his Tractatus de natura salium. In 1660 a second part was added to the Miraculum mundi. Is is apparently only here when Glauber started to make “sal mirabile” (Glauber’s salt) his main focus of his work, replacing niter. (www.encyclopedia.com).
Figure 1: http://www.livingstoneonline.ucl.ac.uk/biog/dl/bio.html
Figure 2: http://www.france24.com/en/20121031-bulgaria-oldest-prehistoric-town-discovered-europe-provadia-solnitsata-ancient-salt-site-archaeology/
Figure 3: http://www.culturaitalia.it/opencms/museid/article.jsp?language=en&article=/en/contenuti/percorsi/percorso197/capitolo_0004.html&tematica=&selected=
Figure 4: http://www.engineerswalk.co.uk/hd_walk.html