hydroxide is settled in large ponds, collected, 
filtered, and washed (Figure 55). The hydroxide is 
neutralized with byproduct hydrochloric acid and 
dried in fluo-solid driers to produce a dry, free- 
flowing hydrous feed for the magnesium cells. 
Electrolysis is conducted in large, bathtub-shaped, 
electrolytic cells filled with a fused salt mixture 
upon which the molten magnesium (liberated 
during electrolysis) floats (Figure 56). The molten 
magnesium is transferred in large crucibles for 
casting metal ingots. 
Figure 56. Electrolytic cell for magnesium ex- 
traction. Cells operate at about 700°C, using 
greater than 100,000 amps of direct current. 
Each cell rests in a brick-lined furnace. Magne- 
sium chloride is fed to cell and electrolyzed to 
magnesium metal and chlorine. (Dow Chemical 
photo) 
2. Bromine 
All facilities directly processing sea water brines 
use a modification of the blowing-out process 
developed originally by Dr. Herbert H. Dow for 
underground brines. In about 1927 when it be- 
came apparent that additional production facilities 
would be required, the process was modified to 
use sea water as a raw material. A plant was 
constructed at Kure Beach, North Carolina, in 
1933, was expanded several times, and operated 
until 1946. Figure 57 shows the Kure Beach plant 
as it appeared in 1940. The present Ethyl-Dow 
bromine production facilities at Freeport, Texas, 
have been operating since 1940 and have been 
enlarged several times. 
In the blowing-out process, incoming sea water 
is screened and acidified to pH 3.5. Chlorine is 
added to oxidize the bromide to bromine, which is 
stripped from the sea water by a countercurrent 
stream of air. The bromine-laden vapor is led into 
a baffled mixing chamber where sulfur dioxide is 
Figure 57. Ethyl-Dow bromine plant at Kure 
Beach, North Carolina, as it appeared in 1940. 
(Dow Chemical photo) 
added, and the reaction products are absorbed in 
an aqueous acid solution. The acid solution is 
rechlorinated and steam-stripped to produce a high 
quality bromine which can be reacted with ethyl- 
ene to produce ethylene dibromide. 
C. Future Extraction of Other Chemicals 
1. Future Possibilities 
Figure 58 shows the abundance of several 
critical elements contained in sea water. Magne- 
sium and bromine also are shown for comparison. 
Uranium is by far the most valuable element per 
cubic mile. Bromine, the least concentrated of the 
commercially produced elements, is over 30,000 
times as plentiful as uranium and over 10 million 
times as plentiful as gold. 
Several sequential operations are required to 
produce a chemical from a raw material like sea 
water. The desired element must be separated, 
concentrated, and processed to a marketable qual- 
ity. Processes have been proposed or developed to 
recover almost all the dissolved elements. How- 
ever, when all costs are considered (e.g., handling 
the large volumes and the amortization and main- 
tenance of the necessary equipment), they cannot 
be supported by the value of the chemicals 
recovered. 
VI-195 
