20
complexes with the lattice ions of the precipitate and by
increasing the total surface area of the dispersed phase.
Goldberg has proposed that the presence of insoluble hydroxides of iron and manganese in ocean waters should give rise
to adsorption phenomena.
The presence of colloidal iron and
manganese in sea water has been reported by Harvey (1937,
1949) and iron by Cooper
in marine waters varies
(1935).
The concentration of iron
from 1 to 100 micrograms per liter.
Much of it must be colloidal or particulate since the solu-
bility products of ferrous and ferric hydroxides in sea water
are such that only 0.5 micrograms per liter can exist as ionic
species,
The charge on ferric hydroxide sols in sea water was
found by Harvey to be positive.
It would, therefore be
expected to scavenge negative ions or ionic complexes.
Harvey reported the manganese content of sea water from
the English Channel to be 7 to 10 micrograms per liter, soluble at pH 4.5.
He suggested that most of it was in the form
of oxide particles with a small, variable quantity in solution.
Goldberg and Arrhenius
(1958) reported a distribution of par-
ticulate and dissolved species of manganese in Pacific Ocean
waters with at least 85 per cent in true golution.
Manganese
hydroxide Mn(OH)4 has a weakly acid character and the hydrosol
is therefore negatively charged (Rankama and Sahama,
1950).