Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts

Details Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts

Nov 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995gecoa..59.4351h&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 59, Issue 21, pp.4351-4365

Computer Science

2

Scientific paper

We report experimental brackets (150-350°C, evacuated silica tubes) on (1) Ag---Cu partitioning between hexagonally close packed (hcp)-, face centered cubic (fcc)-, and body centered cubic (bcc)-(Ag, Cu) 2 S sulfides and the sulfosalts polybasite-pearceite [(Ag 1- x Cu x ) 16 (Sb, As) 2 S 11 , 0.10 > x > 0.57] and high-skinnerite [(Cu 1- x , Ag x ) 3 SbS 3 , x < 0.26] and (2) Ag / Cu ratios of (Ag, Cu 2 S sulfides coexisting with polybasite and skinnerite, and polybasite and pyrargyrite [(Ag 1- x , Cu x ) 3 SbS 3 , x < 0.21]. Based on these brackets on Ag---Cu partitioning and activity-composition models for polybasite-pearceite and high-skinnerite (Harlov and Sack, 1994, 1995) we infer that (1) both hcp- and bcc-(Ag, Cu) 2 S sulfides exhibit positive deviations from ideality sufficient to produce metastable unmixing at slightly less than 90°C and (2) fcc-(Ag, Cu ) 2 S sulfides display more moderate positive deviations from ideal activity-composition relations, characterized by a regular-solution-type parameter, W Ag---Cu fcc = 5.4 ± 0.2 kJ/mol, for an assumed site multiplicity of Ag---Cu mixing of 2. The inferred activity-composition relations for fcc- and bcc-(Ag, Cu) 2 S are consistent with brackets on the T - X Cu systematics of the transition between these phases (Skinner, 1966) and the calorimetric data of Grønvold and Westrum (1986) for Ag 2 S provided that the effective site multiplicity of Ag---Cu mixing in bcc-(Ag, Cu) 2 S decreases linearly from about 3 in Cu-poor to about 2 in Cu-rich compositions ( X Cu ~ 0.315). Our constraints are also consistent with the calorimetric data for Cu 2 S (Grønvold and Westrum, 1987) and Skinner's (1966) brackets on the T - X Cu systematics of the transition between fcc- and hcp-(Cu, Ag) 2 S provided that the effective site multiplicity of Ag---Cu mixing in hcp-(Ag, Cu) 2 S approximates 3. From our brackets on Ag / Cu ratios of (Ag, Cu) 2 S sulfides coexisting with polybasite and skinnerite, and polybasite and pyrargyrite and calibrations for the Ag---Cu exchange reactions we calculate average values of 5.30 ± 1.14 and -31.1 ± 0.7 kJ/mol for the Gibbs energies of formation of hypothetical Cu 16 Sb 2 S 11 and Ag 16 Sb 2 S 11 polybasite components from the simple sulfides over the temperature range 150-350°C.

Affiliated with

Also associated with

No associations

Rating

Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermochemistry of Ag 2 S---Cu 2 S sulfide solutions: Constraints derived from coexisting Sb 2 S 3 - and As 2 S 3 -bearing sulfosalts will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1180288