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Selected methods for dissolved iron (II, III) and dissolved sulfide (-II) determinations in geothermal waters

Water-Resources Investigations Report 85-4189

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Abstract

Dissolved sulfide (-II) and dissolved iron (II, III) were determined in geothermal well water samples collected at Cerro Prieto, Mexico. Most samples consisted of liquid and gas (two phases) at the instant of collection; and a subset of samples, referred to as ' flashed ' samples, consisted of pressurized steam samples which were allowed to condense. Sulfide was determined by sulfide specific ion electrode; Fe(II) and Fe(III) plus Fe(II) were determined spectrophotometrically. The precision and accuracy of the methods were evaluated for these high-silica waters with replicate analyses, spike recoveries, and an alternate method. Direct current (d.c.) argon plasma emission spectrometry was the alternate method used for Fe(III)-plus-Fe(II) analyses. Mean dissolved iron concentrations ranged from 20.2 to 834 micrograms/L (ug/L) as Fe(II) and 26.8 to 904 ug/L as Fe(III) plus Fe(II). Mean sulfide concentrations ranged from about 0.01 to 5.3 mg/L (S-II) Generally, higher S(-II) values and larger Fe(II)/Fe(III) ratios were found in the two-phase samples. These findings suggest that the ' flashed ' samples are at a less reduced state than the two-phase samples. (Author 's abstract)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Selected methods for dissolved iron (II, III) and dissolved sulfide (-II) determinations in geothermal waters
Series title:
Water-Resources Investigations Report
Series number:
85-4189
Edition:
-
Year Published:
1985
Language:
ENGLISH
Publisher:
U.S. Geological Survey ; Open-File Services Section, Western Distribution Branch, U.S. Geological Survey [distributor],
Description:
iv, 16 p. ;28 cm.