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Etude par spectroscopie Raman de l'influence de la pression sur l'association de l'ion thiocyanate avec divers cations metalliques en solution aqueuse
Author(s) -
Manouvrier E.,
Devaure J.
Publication year - 1978
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250070207
Subject(s) - chemistry , molality , raman spectroscopy , thiocyanate , ion , metal , analytical chemistry (journal) , dissociation (chemistry) , inorganic chemistry , aqueous solution , chromatography , optics , physics , organic chemistry
Using Raman spectroscopy we have investigated the effect of pressure on the association between the thiocyanate ion and some metallic cations: Zn 2 + , Mn 2 + , Al 3 + , In 3 + , Th 4 + , Hg 2 + . The ν(CS) stretching vibration of the anion has been analysed because of its sensitivity to the complexation; new ν(CS) lines appear at frequencies well distinct from that of the free ν(CS). The quantity of free SCN − has been determined from the intensity of the free ν(CS) line and has been used to calculate the formation constants for the equilibria M x + + n SCN − ⇄M(SCN) n (x‐n) + . Values have been obtained at normal pressure and at 3000 atmospheres. Finally, the mean value of the change of the partial molal volume Δ V for the complexation reaction between the two extreme pressures has been calculated. The dissociation of the complexes is generally favoured by an increase of the pressure, and the Δ V values are positive. We think that the largest measured values of Δ V are due to a change of the coordination number of the cation on complexation.