Original paper
Thallium sulphosalts, their phase diagrams and the affinity problem
Gržetić, Ivan
Neues Jahrbuch für Mineralogie - Abhandlungen Band 166 Heft 1 (1993), p. 15 - 24
8 references
published: Dec 9, 1993
ArtNo. ESP154016601004, Price: 29.00 €
Abstract
In spite of the considerable research on sulphide minerals very little thermodynamical informations are available for most of the sulphosalts. First order thermodynamic approximation, possible only in those cases when the cation polyhedra of the complex sulphides approximate the cation polyhedra of the simple sulphides, served as a good base for the investigation of the mutual affinity of sulphides within certain phase assemblages described by appropriate phase diagram. The used approximation procedure appears to be the most useful with relatively simple algorithm. It is known under the name “sulphide sum” method developed by Craig & Barton (1973). In ternary system the magnitude of the free energy of formation (ΔGi) of the binary compound i, present in this system, defines the extent of affinity of two end members, one to another, which build the investigated binary compound. Comparison of affinities between Ag2S and As2S3 or Tl2S and As2S3 within the Ag2S-Tl2S-As2S3 system, as well as Ag2S and Sb2S3 or Tl2S and Sb2S3 within Ag2S-Tl2S-Sb2S3 system gave interesting results. The affinity of As2S3 to Ag2S is lower than to Tl2S in Ag2S-Tl2S-As2S3. The affinity of Sb2S3 to Ag2S is smaller than to Tl2S in Ag2S-Tl2S-Sb2S3 system. Between three end members, those two, which have more negative ΔG, will give more stable binary compounds. The affinity between two endmembers, which have the most negative ΔG, is greater than between any of these two end-members to the third end-member, which have less negative ΔG, in the investigated ternary system.
Keywords
Thallium sulphosalts • affinity • thermodynamic calculations