Element	Metal oxide or hydroxide	Precipitation pH	Highest precip	Lowest Precip	Presence in sea water (ppm)
Niobium	Nb 5+	1 to 10	10	1
Tantalium	Ta 5+	1 to 10	10	1
Hafnium	Hf 4+	6 to 7	7	6
Indium	In 3+	6 to 13	13	6
Iridium	Ir 4+	6 to 8	8	6
Rhenium	Re 3+	6 and up   1N	14	6
Thorium	Th 4+	6 and up   1N	14	6
Zirconium	Zr 4+	6 to 7	7	6
Aluminum	Al 3+	7 to 8	8	7
Antimony	Sb 3+	7 to 8	8	7
Antimony	Sb 5+	7 to 8	8	7
Beryllium	Be 2+	7 to 8=7F	8	7
Bismuth	Bi 3+	7 and up   1N	14	7
Cadmium	Cd 2+	7 and up   1N	14	7
Chromium	Cr 3+	7 and up   1N	14	7
Copper	Cu 2+	7 and up   1N	14	7
Gallium	Ga 3+	7 to 8	8	7
Gold	Au 3+	7 to 8	8	7
Iron	Fe 2+	7 and up   1N	14	7
Lead	Pb 2+	7 to 8	8	7
Manganese	Mn 4+	7 and up   1N	14	7
Osmium	Os 4+	7 to 8	8	7
Paladium	Pd 2+	7 to 8	8	7
Paladium	Pd 4+	7 to 8	8	7
Platinum	Pt 2+	7 to 8	8	7
Rhodium	Rh 3+	7 to 8	8	7
Ruthenium	Ru 3+	7 and up   1N	14	7
Tin	Sn 2+	7 to 8	8	7
Tin	Sn 4+	7 to 8	8	7
Vanadium	V  4+	7 to 8	8	7
Vanadium	V  5+	7 to 8	8	7
Zinc	Zn 2+	7 to 8	8	7
Cobalt	Co 2+	8 and up   1N	14	8	.0001
Manganese	Mn 2+	8 and up   1N	14	8	.001-.01
Mercury	Hg 1+	8 and up   1N	14	8	.0003
Mercury	Hg 2+	8 and up   1N	14	8	.0003
Nickel	Ni 2+	8 and up   1N	14	8	.0001-.0005
Scandium	Sc 3+	8 and up   1N	14	8	not detected
Titanium	Ti 3+	8 and up   1N	14	8	present
Titanium	Ti 4+	8 and up   1N	14	8	present
Copper	Cu 1+	9 and up   1N	14	9	.001-.09
Magnesium	Mg 2+	9 and up   1N	14	9	1272
Silver	Ag 1+	pH 9 and up   1N	14	9	.00015-.0003
Thallium	Tl 3+	9 and up   1N	14	9	not detected

THE pH OF NATURAL MEDIA AND ITS RELATION TO THE PRECIPITATION OF HYDROXIDES