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ISSUE ONE (MAY 2000)

NOTES & QUERIES

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Pin!!Bea Hopkinson writes:

Salt: everything has its place

   A lot of nonsense is circulated about salt, for and against, so I am pleased to attempt a balanced view.

   Because salt is an antiseptic and kills bacteria, it has been used in purification rites in Anglo-Saxon religious services. It was natural, therefore, to think that places where salt occurred were holy places if there was some beneficial effect. However, beneficial effects can also occur with other fresh?/mineral waters, viz: Lourdes, Bath. How valid this is can only be testified to by the beneficiaries themselves (spiritual or otherwise).

   It is true to say that too much salt can be as bad as too little. The beneficial effects of salt in agriculture are well known, but too much, as you say, can kill plants. I am not sure you can "adapt" plants to a saline environment. They are either physiologically halophylic and can tolerate (dispense/exude/express) surplus salt taken in, or die. Certain eels are physically adapted to cope with both fresh and salt water. The reason that you find plants in salt marshes is that this is a diluted freshwater/saltwater boundary where freshwater drainage from the land meets the ocean. In any case, seawater contains only 3.5% dissolved solids of which 2.9% is sodium chloride.

   We can compare this with the Droitwich brine springs that contain almost 26% sodium chloride (where it was extremely economic to produce extremely pure salt !). That is, it is unusual in nature to find such a pure source of brine available in the form of sub-artesian springs so close the surface which are easy to exploit simply by boiling, and without the need to refine.

   Minerals in nature combine in different ways to produce different salts depending on the concentration of the minerals present in solution. Temperature can also have an effect on how elemental chemicals combine. Thus we find surface springs (around which wells or wood-lined pits were built) can contain different minerals depending on the source of the water and its mineral content, and the mineral content of the ground over which it travels. At Droitwich there is a pure salt deposit only about 200 feet below the surface. This is dissolved by water from the Lickey's 20 miles away. Because this water is 'soft' and contains few minerals, and the rock salt itself is relatively pure, the resulting brine becomes fully saturated and, therefore, can pick up no additional minerals on its way to the surface. Hence an extremely pure, almost fully saturated brine in the springs.

   As far back as we can trace early man recovered salt from natural salt resources for a number of different reasons: sometimes because of a biological need according to a diet, say high in grain (animals often exhibit a need for salt for this reason - Jane Goodall's chimpanzees for example); to preserve surplus food; to glaze pots for practical and decorative purposes, etc.etc. The uses for salt change over time due, for example, the invention of refrigeration in the 20th century. Nevertheless, the number of uses to which salt is put have not been reduced with time, in fact their number and diversity seems to have increased with new technology.

   The aspect of salt recovery that seems to be little understood, is that although salt is prevalent in nature it cannot always be recovered and processed economically. In this sense salt is geographically limited. Thus, as permanent settlements developed and salt had to be obtained through trade, specialists developed who recovered and refined salt at sites where salt could be produced economically, which were close to centres of settlement. An important factor in this development was the availability of cheap fuel. Or in the places where solar evaporation was possible, sufficiently long dry periods (and wind conditions) in the summer to crystallise salt, but even then fuel was needed to refine this crude salt.

   So you might say, everything has its place, including salt.

The above is not for reproduction without permission of the author.

 

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