An investigation of certain complex ions of trivalent chromium by spectrophotometric and other physical methods

Abstract

Although chromium coordination compounds are of considerable technological importance, they have been subjected to few thorough investigations since Werner's original experlments, in spite of the fact that we now possess a number of accurate physical methods, not available in Werner's time for the study of coordination complexes, The object of the work described in this thesis was to obtain further information on the chemistry of complex chromium(III) ions with special reference to the dioxalato-diaquochromiate system, [Cr(Câ‚‚0â‚„)â‚‚(Hâ‚‚0)â‚‚]. For this purpose; spectrophotometric and potentlometrlc measurements were combined to yield information on a number of topics, The spectrophotometric investigations consisted in measuring the absorption spectra of the potassium salts of the complexes under consideration and in observing the changes in light absorption which occur during their formatlon and decomposition. The instrument used was a Beckmann Quartz Spectrophotometer model du. More than than twelve new absorption spectra were measured in this work and in conjunction with the spectra of other chromium and cobalt complexes reported by earlier workers, these are used to review the position of spectrophotometry as a method of investigating chromium complexes. The reasons for the shapes of the absorption spectra are discussed and it is concluded that spectrophotometry is useful for observing the progress of reactions involving complex ions and for analysing solutions, but that more fundamental data cannot be expected from the absorption curves.