Home' Salt : Salt Contents from the source 149
iodised salt, a small amount of sugar which prevents the loss of iodine and stops
the salt yellowing, and probably an anti-caking agent such as calcium silicate or
a compound of aluminium. All of the other minerals that are found naturally
in sea water will have been removed in the refining process.
Because sea water does not just contain sodium chloride. There are another 83
naturally occurring minerals to be found in the world's oceans: sodium chloride
is simply the most numerous of them, comprising over 75% of the suspended solids.
Which is why sea water tastes salty, and why 'natural' sea salt will contain not just
sodium chloride but also magnesium, calcium, potassium, iron and iodine, along
with trace amounts of a number of other minerals.
A Wealth of Salt
Depending on where you are, if you should dip a cup into the sea the water you
scoop up will contain between 1% and 5% sodium chloride: the lesser figure if you
are near the north or south pole, and the greater in any small, enclosed sea such as
The average salinity of seawater is therefore around 2.5%. If your cup had a capacity
of 4 litres, then on average the water you had scooped up would yield, after evapora-
tion, approximately 105 grams of salt. On a slightly different scale, if you evaporated
one cubic kilometre of sea water it would leave 26 metric tons of salt.
And if you evaporated all of the world's oceans, the remaining salt would equal
almost 15 times the mass of continental Europe.
The amounts are sta gering, the supply of salt seemingly inexhaustible. Yet human
history may be seen in one light as little more than the continuing quest for salt.
If salt is indeed so plentiful, why has the finding and the extracting of it required so
much effort and ingenuity? As Mark Kurlansky writes in Salt: A World History, likely
to remain the definitive work on the subject, "for all of history until the twentieth
century, salt was desperately searched for, traded for, and fought over. For millenia,
salt represented wealth." Yet it is something that, again in Kurlansky's words, "fills
the ocean, bubbles up from springs, forms crusts in lake beds, and thickly veins a
large part of the earth's rock fairly close to the surface."
The reason is that the amount of salt that is easily accessible has never been enough
to satisfy demand. People need salt, and as civilisation progressed, the need for salt
progressed along with it.
This human requirement for salt can, presumably, be traced back to the successful
transition of life from sea to land over 300 million years ago. For that transition to
be successful, bodily cells had to be bathed in a salty solution similar to seawater.
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