'THE GEOLOGY AND MINERAL RESOURCES OF DHUFAR PROVINCE, MUSCAT AND OMAN' [‎52v] (94/96)

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As the sea-water in the salt pans evaporates and thus concentrates to brine,
there comes a stage when Sodium chloride or common salt precipitates (crystallizes)
and can be removed. The brine is unsaturated until it contains 17% of salts (at
about 15 degrees Centigrade), but between 17 degrees Beaume and 25 degrees Beaume
it is saturated so far as Calcium sulphate is concerned, and the brine is in a meta
stable state. Between 25 and 29-5 degrees Beaume the brine is in a labile state as
far as Sodium chloride is concerned, and with higher concentration, up to 38-5 degrees
Beaume, this salt separates.
As the sea-water in the salterns concentrates to brine by evaporation, so differences
in the solubility of the dissolved salts become effective. At an early stage, 11 degrees
Beaume, the Calcium carbonate precipitates. Next, between 17 and 25 degrees
Beaume, the Calcium sulphate (as Gypsum) separates out. The Sodium chloride
reaches its unstable saturation between 25 and 30 degrees Beaume during which this
salt crystallizes. Experience shows that the evaporation of sea-water is, in its less
concentrated state, quicker than fresh water when exposed to the sun and wind in
open sheets of water. It is thought that in suitable weather this evaporation may
be one inch in three days. On the shores of Risut bay the evaporation would
probably average 275 feet between October and March, 3-25 feet from April to
June and 0-5 feet from July to September (7-5 feet total).
Salt (Sodium chloride) is prepared at Kharain during January to June in small
quantities, and there is little doubt that, if the necessary care was exercised, larger
quantities of superior quality may be prepared on the northern shore of Risut bay.
If the quantity of good quality salt was sufficient, it should be possible to manu
facture Soda Ash (Sodium carbonate) and other chemicals near Salalah. It is, how
ever, not possible to estimate the quantities and cost of manufacture of the salt
without fuller data on the cloudy and rainy days on the one hand and the effect of
rain and flood water in diluting the sea-water of Risut bay on the other. The
impounding of the flood water in the wadi A seasonal or intermittent watercourse, or the valley in which it flows. Nagar Ghaiz has been considered from a
water-supply point of view, and this would reduce the dilution of the sea-water in
Risut while at the same time providing fresh water.
It is not to be presumed that Dhufar is the most suitable coast in the Sultanate
of Oman for the manufacture of salt. A typical site would appear to be along the
coast of the gulf of Masira half-way between Salalah and Muscat. The salt plain of
Bar al Hikman, on the mainland opposite Masira island between Ghubat Hashish and
the Masira channel, would appear to be more satisfactory. There is likely to be
less cloudiness and little alteration of the sea-water during the south-west monsoon
rains. It is one of the most desolate-looking regions on the coast of Oman and,
for this reason, prove unattractive for the site of a large chemical works. Should
limestone and sufticient fresh water be procurable in the vicinity, Bar al Hikman
might be the best place for preparing Soda Ash as it is certainly a better place for
making salt although 400 miles from Salalah.
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