122
T/zc Last Resource
from the sea—water by acidifying it with sulphuric acid and then
chlorinating it. Sea—water treated in this way is passed down a tower
against a current of air which blows out the bromine. The bromine
and water—vapour mixture is reacted With sulphur dioxide to yield
hydrobromic and sulphuric acids. The mixture is then treated with
chlorine and steam. The free bromine from this is collected and
condensed while the recovered sulphuric acid and hydrochloric acid
from the steam and chlorine treatment are used to process more
in—coming sea—water. In the case of the Dow process the bromine is
puried and reacted with the organic compound ethylene to give
ethylene dibromide (see gure 12).
The Dow plant for the extraction of magnesium, also set up at
Freeport, starts from two raw materials—sea—water and oyster shells
mined from the oor of the Gulf of Mexico. The shells are burnt to
produce lime which is added to the sea—water in giant settling tanks
where a deposit of insoluble magnesium hydroxide slowly collects.
Hydrochloric acid is added to this slurry to produce magnesium
chloride which is extracted and dried. The magnesium is nally
separated from the chlorine by electrical means and is made up into
ingots, while the chlorine is converted to hydrochloric acid and
returned once more to the start of the cycle (see gure 13). In other
systems of extracting magnesium—usually as the oxide, magnesia—
the sea—water is mixed With a lime produced from dolomite (calcium
magnesium carbonate) instead of shells. Plants working on this
principle are found, for example, at Moss Landing in California and
'
Hartlepool in England. With these facilities for extracting
magnesium from sea—water, a cubic mile of which contains over four
million tons or several times the annual world production of the
metal, future supplies are assured and there seems no need to look
for further sources on the land.
So much for the chemicals already taken in large quantities from
sea—water; are there any others that might be extracted in the future.P
As mentioned at the beginning of this chapter, the Germans did at
one time consider removing gold from sea—water. In fact the brilliant
German chemist and Nobel laureate Dr Fritz Haber devoted some
ten years to the problem. He nally concluded that the amounts of
the metal dissolved in sea—water—a millionth of a gram per cubic
metre—were
generally well below previous estimates and the
project was abandoned. ln fact 0-09 milligrams of gold, obtained by
Dow by processing about I 5 tons of sea—water, probably represents
T/zc Last Resource
from the sea—water by acidifying it with sulphuric acid and then
chlorinating it. Sea—water treated in this way is passed down a tower
against a current of air which blows out the bromine. The bromine
and water—vapour mixture is reacted With sulphur dioxide to yield
hydrobromic and sulphuric acids. The mixture is then treated with
chlorine and steam. The free bromine from this is collected and
condensed while the recovered sulphuric acid and hydrochloric acid
from the steam and chlorine treatment are used to process more
in—coming sea—water. In the case of the Dow process the bromine is
puried and reacted with the organic compound ethylene to give
ethylene dibromide (see gure 12).
The Dow plant for the extraction of magnesium, also set up at
Freeport, starts from two raw materials—sea—water and oyster shells
mined from the oor of the Gulf of Mexico. The shells are burnt to
produce lime which is added to the sea—water in giant settling tanks
where a deposit of insoluble magnesium hydroxide slowly collects.
Hydrochloric acid is added to this slurry to produce magnesium
chloride which is extracted and dried. The magnesium is nally
separated from the chlorine by electrical means and is made up into
ingots, while the chlorine is converted to hydrochloric acid and
returned once more to the start of the cycle (see gure 13). In other
systems of extracting magnesium—usually as the oxide, magnesia—
the sea—water is mixed With a lime produced from dolomite (calcium
magnesium carbonate) instead of shells. Plants working on this
principle are found, for example, at Moss Landing in California and
'
Hartlepool in England. With these facilities for extracting
magnesium from sea—water, a cubic mile of which contains over four
million tons or several times the annual world production of the
metal, future supplies are assured and there seems no need to look
for further sources on the land.
So much for the chemicals already taken in large quantities from
sea—water; are there any others that might be extracted in the future.P
As mentioned at the beginning of this chapter, the Germans did at
one time consider removing gold from sea—water. In fact the brilliant
German chemist and Nobel laureate Dr Fritz Haber devoted some
ten years to the problem. He nally concluded that the amounts of
the metal dissolved in sea—water—a millionth of a gram per cubic
metre—were
generally well below previous estimates and the
project was abandoned. ln fact 0-09 milligrams of gold, obtained by
Dow by processing about I 5 tons of sea—water, probably represents