The solubility of amorphous As sub 2 S sub 3 from 25 to 90C

Journal Article · Mon Jun 01 00:00:00 EDT 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90188-O· OSTI ID:5041153

Eary, L E ^[1]

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1. Pacific Northwest Lab., Richland, WA (United States)

The solubility of amorphous arsenic sulfide (As{sub 2}S{sub 3}(am)) has been experimentally determined from 25 to 90C. In acidic, sulfide-deficient solutions, H{sub 3}AsO{sub 3}{sup 0} is the dominant product of As{sub 2}S{sub 3}(am) dissolution: 1/2 As{sub 2}S{sub 3}(am) + 3 H{sub 2}O = H{sub 3}AsO{sub 3}{sup 0} + 3/2 H{sub 2}S{sup 0}. The respective logarithms of equilibrium constants for this reaction are {minus}11.9 {plus minus} 0.3 at 25C, {minus}11.2 {plus minus} 0.2 at 40C, {minus}10.2 {plus minus} 0.1 at 60C, and {minus}9.0 {plus minus} 0.2 at 90C, all at 0.1 m ionic strength. In acidic solutions with excess sulfide, experimental data are consistent with H{sub 2}As{sub 3}S{sub 6}{sup {minus}} being the dominant dissolved As species: 3/2 As{sub 2}S{sub 3}(am) + 3/2 H{sub 2}S{sup 0} = H{sub 2}As{sub 3}S{sub 6}{sup {minus}} + H{sup +}. The respective logarithms of equilibrium constants for this reaction are {minus}5.0 {plus minus} 0.3 at 25C, {minus}5.1 {plus minus} 0.3 at 40C, {minus}4.9 {plus minus} 0.2 at 60C, and {minus}4.1 {plus minus} 0.1 at 90C, all at 0.1 m ionic strength. Speciation calculations for a number of acidic hot springs indicate that many have As and H{sub 2}S{sup 0} concentrations that are bracketed by the solubilities of As{sub 2}S{sub 3}(am) and orpiment and that H{sub 3}AsO{sup 0}{sub 3} is generally the dominant dissolved As species. The solubility data indicate that lowering of temperature and pH are the most likely mechanisms of As{sub 2}S{sub 3}(am) precipitation in hot spring systems.

• OSTI ID: 5041153
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 56:6; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
ARSENIC SULFIDES
SOLUBILITY
AQUEOUS SOLUTIONS
ARSONIC ACIDS
CHEMICAL REACTIONS
DATA ANALYSIS
DISSOLUTION
EQUILIBRIUM
EXPERIMENTAL DATA
HOT SPRINGS
HYDROGEN SULFIDES
KINETICS
PH VALUE
PRECIPITATION
RESERVOIR TEMPERATURE
TEMPERATURE RANGE 0273-0400 K
THERMODYNAMIC PROPERTIES
ARSENIC COMPOUNDS
CHALCOGENIDES
DATA
DISPERSIONS
HYDROGEN COMPOUNDS
INFORMATION
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC ARSENIC COMPOUNDS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SEPARATION PROCESSES
SOLUTIONS
SULFIDES
SULFUR COMPOUNDS
TEMPERATURE RANGE
THERMAL SPRINGS
WATER SPRINGS
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