SALT.... made the world go round

Prometheus is often described as the bringer of fire for the benefit of mankind. But a study of Greek and Roman firemaking techniques and myths suggests that this interpretation may be incorrect. Prometheus did not bring the flame itself; he brought the secret of "catching" sparks. By chance, perhaps, man discovered that some everyday materials were particularly good tinder for kindling fires and learned to select those, such as dried moss and fungus, with enough protein matter for conversion into nitrates through decomposition. Certainly nitrates will help to ignite dry cellulose material more easily by supplementing the oxygen in the air at the critical moment of starting the flame. Animal dung is another useful source of fuel and we may assume that neolithic farmers recognised its value, for tinder has been found together with flints and pyrites dating from about 700 BC in Yorkshire, England, suggesting that it was a primitive method of firemaking.

Besides selecting their raw materials carefully, the ancients learned to improve on nature by saturating the tinder with blood and urine ,mixed with potash-rich ashes. Later, this slow biological action was speeded up in 'nitre beds' - the waste and plant ashes were heaped up together, exposed to the air and watered at intervals. Eventually after the piles had been turned many times, this manure produced saltpetre.

SALTPETER MAKING

Nitre, potassium nitrate KNO3, more commonly known as saltpetre, is formed in warm climates by bacterial action during the decomposition of excreta and vegetable refuse. Where people and animals live in close proximity, debris accumulates in and around their homes. The contact between putrefying material, alkaline soil, plant ashes, air and moisture allows 'nitrification' - that is the conversion of nitrogen compounds from animal and plant decay into nitrates which penetrate the soil. Dissolved in rainwater, the deposits evaporate on the surface to form crude saltpetre, as a white flower like powder. This must be washed to remove earth and impurities; then boiled and evaporated to refine it.

TINDER

There is no information about artificial nitrate impregnation of combustible matter in prehistoric times and the composition of tinder was always a jealously kept secret. But in primitive practice 'good' tinder can be made better by soaking the firing materials in a solution of saltpetre. Kindling wood is still used by a central African tribe to make fire by friction with a quickly rotating stick. Tests have shown that, extracted by hot water, these sticks proved to contain 0.65% saltpetre and 0.05% sodium carbonate. The K -ion being necessary to prevent the tinder from attracting moisture from the air. Potassium nitrate is not deliquescent; but other nitrates such as sodium for instance, are susceptable to external humidity.

Saltpetre impregnated fungus - Polyphorus fomentarius - known all over Europe as 'amadoo' - was widely used as tinder from early times. It was collected from old trees and treated by boiling, soaking in saltpetre, then dried and used in a tinder box. This contained flint, steel and material - the tinder - to ignite easily and was an essential household article before the invention of matches as well as a personal possession as the cigarette lighter is today.

BIOLOGICAL MANUFACTURE

Although common salt -NaCl - is certainly the most important of the alkalis, the developing trade and industries of the post-glacial civilizations also made extensive use of potasssium, sodium carbonate and nitrate for ceramics, soap, glass, medication and as a fertilizer. It seems astonishing that until about the time of the French Revolution they were still produced through the natural activity of living organisms where enzymes and membranes serve to separate the alkalis from each other and from the inorganic ions accompanying them. For instance, they allow potassium to combine with organic acids instead of with chlorine. The energy for making these organic acids comes from the sun and the raw materials are carbon dioxide and water - in other words photosynthesis. Simultaneously, the inorganic anions - the chlorides and sulphates - are rejected. So when plants are burnt and the organic acids with them, the potassium ends up as potassium carbonate in the ash - that is, as potash - and in the case of the rarer salt-loving plants, the sodium becomes soda ash. Rich carbonate sources are found in natural alkaline lakes in many parts of the world; but even there the salts result from natural action.

Climate influenced saltpetre manufacture and determined its location. The temperate regions had forests and grasslands which provided potash and good grazing for cattle but were poor in nitrates. In the arid zones, potash from lakes, good irrigation and most of all warmth, to help quick fermentation, favoured early and easier development of saltpetre..

SALTPETER FACTORIES AT THE DEAD SEA

One of the most ancient potash sources, the Dead Sea, provided the salts for a saltpetre operation near Ein Bokek, or as it is sometimes called, Um Barak, on the western shore. This is a spring lying a hundred metres above a ruined castle about two hundred metres north of Wadi Ein Bokek. Originally, the castle was one of a chain of fortresses surrounding the Dead Sea, built about the second century AD, to protect the salt trade. Sometime during its history, within the old walls , a saltpetre factory produced several tons a year. The nearby spring supplied fresh water for the cattle grazing on the lush green grass converting it into valuable nitrogenous sewage which trickled down into the castle courtyard. There, mixed with limestone marl from the deposits at Lissan on the opposite shore, it was left to accumulate and decompose. The resulting nitrates came in contact with wood ash and the Dead Sea salts - sodium and potassium - and , it seems, were refined in the castle itself, forming saltpetre which can still be scraped up. A similar 'officina' or factory complex existed on the south side of the Wadi conveniently near the sea shore where potassium chloride was made by solar evaporation and where flotsam and jetsam could be gathered for fuel. Some of the compost may have come from the grazing grounds, but probably the officina had its own supply on the shore line slopes where a canal diverted the Ein Bokek stream to irrigate more pasture for animals. From there the sewage was conducted into cisterns - still visible - to be nitrified with marl.

Avdat, Petra, Beth Jibrine and the Carmel near Haifa have all been identified by the deposits on the cave walls and floors as 'barud' or gunpowder factories where successive generations of Byzantine, Mamlukes and Turks worked to produce the most important constituent needed for gunpowder

One of the most important rock sources of Potassium Chloride and NaCl salt was Mount Sdom by the Dead Sea which is almost solid precipitated salt

Mount Sdom - view towards the Dead Sea- from the direction of Herod's hill fort Masada, which probably protected the salt traffic from the mountain, up to Jerusalem