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ArticleName Potentiometer study of the process of complexation of silver (I) ions with thiourea
DOI 10.17580/tsm.2021.09.02
ArticleAuthor Samadov A. S., Gorichev I. G., Eliseeva E. A., Boldyrev V. S.

Moscow State Pedagogical University, Moscow, Russia:

A. S. Samadov, Graduate Student of the Chair for General Chemistry, e-mail:
I. G. Gorichev, Professor of the Chair for General Chemistry, Doctor of Chemistry Sciences , e-mail:


Bauman MSTU, Moscow, Russia:
E. A. Eliseeva, Associate Professor of the Chair for Chemistry, Candidate of Chemistry Sciences, e-mail:
V. S. Boldyrev, Associate Professor of the Chair for Chemistry, Candidate of Technical Sciences, e-mail:


The process of complexation of silver(I) ions with thiourea (Tu) in the temperature range 287.16–318.16 K at an ionic strength of 0.11 M (I = 0.1 NaNO3 + 0.01 HNO3) was studied by the potentiometric method using a silver electrode in aqueous solution. The study was performed at a concentration of silver(I) ions CAg+ = 1 · 10–5 and CAg+ = 1 · 10–3 M. The values of the stability constants of AgTui + complexes (i = 1–2) were estimated at CAg+ = 1 · 10–5 M. The AgTu3+ complex constant was determined at CAg+ = 1 · 10–3 M and CTu ≥ 0.01 M. The stability constants of complexes were calculated using the Leden method. The values of the complex constants at 298.16 K are equal to: lgβ1 = 5.59 ± 0.10 (AgTu+), lgβ2 = 10.62 ± 0.03 (AgTu2+) and lgβ3 = 13.05±0.11 (AgTu3+). It is established that the temperature effect does not affect the number of formed particles in the solution; an increase in temperature leads to a decrease in the stability of complexes. The analysis of the values of the stability constants by degrees shows that the step constants AgTu3+ (AgTu2+ + Tu = AgTu3+ + lgβ3 = 2.4) are much smaller than the constants for mono- and bis-coordinated complexes. The complexes thermodynamic parameters (ΔH0, ΔG0, ΔS0) were calculated by the temperature coefficient method. In the system under study, all complexation reactions are exothermic. The largest increase in the value of enthalpy (ΔH0) is observed in the formation of a complex containing two molecules of thiourea. The change in entropy (ΔS0) at the stage of formation of bis- and tris-coordinated complexes is negative, which is most likely due to a decrease in the number of particles in the system under study. It is determined that enthalpy-entropy dependences show a monotonic character. The spontaneous course of complexation reactions is determined by the value of the free Gibbs energy (ΔG0). In degrees G0 decreases (ΔG0)1 < (ΔG0)2 < (ΔG0)3) and has a negative value, which indicates a decrease in the affinity of the complexing agent to the ligand.

keywords Complexation, silver (I) ions, thiourea (Tu), stability constants, thermodynamic parameters, potentiometry

1. Kotlyar Yu. А., Meretukov М. А. Metallurgy of precious metals. Moscow : ASMI, 2002. 466 p.
2. Calla-Choque D., Lapidus G. T. Acid decomposition and silver leaching with thiourea and oxalate from an industrial jarosite sample. Hydrometallurgy. 2020. Vol. 192. P. N. 105289.
3. Dovnar R. I., Smotrin S. М. The use of silver in medicine: Historical aspects and a current view on the problem. Problemy zdorovya i ekologii. 2011. No. 3. pp. 149–153.
4. Shuiping C. Guozhong W. Hongyan Z. Preparation of high antimicrobial activity thiourea chitosan–Ag+ complex. Carbohydrate Polymers. 2005. Vol. 60. pp. 33–38.
5. Bessen N. P., Jackson J. A., Jensen M. P., Shafer J. C. Sulfur donating extractants for the separation of trivalent actinides and lanthanides. Coordination Chemistry Reviews. 2020. Vol. 421. p. 213446.
6. Mironov I. V., Tsvelodub L. D. Stability of mononuclear and binuclear complexes of silver(I) with thiourea in aqueous solution. Zhurnal neorganicheskoy khimii. 1996. Vol. 41. No. 2. pp. 240–244.
7. Samadov А. S., Mironov I. V., Gorichev I. G., Kovalchukova О. V., Stepnova А. F. Study of complexation of silver (I) with some thiourea derivatives in aqueous solution. Zhurnal obshchey khimii. 2020. Vol. 90. No. 11. pp. 1738–1742.
8. Krzewska S., Podsiadly H. Complexes of Ag(I) with ligands coivtaining sulphsjr donor atoms. Polyhedron. 1986. Vol. 5. No. 4. pp. 937–944.
9. Lukinskas I. S., Vita S., Arunas L. Potentiometric study of silver complexes with thiourea in acid media. Journal of Coordination Chemistry. 2008. Vol. 61. No. 16. pp. 2528–2535.
10. Domenico De Marco. Isoequilibrium and free energy relationships in complex formation equilibria between Ag(I) and thiocarbonyl ligands in oxygenated solvent media. Journal of Coordination Chemistry. 2017. Vol. 70, Iss. 6. pp. 1053–1065.
11. Bowmaker G. A., Chaveng P., Saowanit S., Brian W. S., White A. H. 1 : 1 complexes of silver(I) thiocyanate with (substituted) thiourea ligands. 2009. Dalton Trans. Vol. 14. pp. 2588–2598.
12. Meena K., Muthu K., Rajasekar M., Meenatchi V., Meenakshisundaram S. P. et al. Growth, structure, and characterization of tris(thiourea) silver(I) nitrate. Journal of Thermal Analysis and Calorimetry. 2013. Vol. 112. pp. 1077–1082.
13. Bellomo A., De Marco D., De Robertis A. Formation and thermodynamic properties of complexes of Ag(I) with thiourea as ligand. Talanta. 1973. Vol. 20. pp. 1225–1228.
14. Samadov А. S., Mironov I. V., Gorichev I. G., Stepnova А. F. Study of equilibria of complexation of silver (I) ions with N-phenylthiourea in aqueous solution. Zhurnal neorganicheskoy khimii. 2020. Vol. 65, No. 7. pp. 995–999.
15. Fupeng Liu, Jinliang Wang, Chao Peng, Zhihong Liu, Wilson B. P. et al. Recovery and separation of silver and mercury from hazardous zinc renery residues produced by zinc oxygen pressure leaching. Hydrometallurgy. 2019. Vol. 185. pp. 38–45.
16. Safarmamadov S. М., Muborakkadamov D. А., Mabatkadamova К. S. Complexation of gold (III) with 1-furfurylidenamino-1,3,4-triazole at 288–318 K. Izvestiya vuzov. Khimiya i khimicheskaya tekhnologiya. 2017. Vol. 60, Iss. 5. pp. 37–43.

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