Studies on metal hydroxy compounds. XII. Thermal analyses, decomposition kinetics, and infrared spectra of copper basic oxysalts

Abstract

The thermal analyses of copper basic oxysalts of the type Cu?(OH),XO,, where X = S, C, C1, Br! I, N, H C and y = 4, 3, or 2 reveal that decomposition occurs, In most cases, by dehydroxylatlon w~t h concomitant disproportionation of the oxysalt. An outstanding exception to this pattern of decornposition is the basic sulfate. Calorimetric measurements along with related enthalpic values for the decornposition reaction are given.The kinetics of thermal decomposition of the compounds are classified into three main categories: (i) three-dimensional contracting sphere model, (ii) first-order rate, and (iii) nucleation controlled rate processes.The infrared spectral data of nine copper basic oxycompounds in the frequency region 4000-250 cm-' are presented with their assignments. The fundamental infrared inactive modes of the anionic species SO,'-, NO3-, etc. become active by the presence of the copper hydroxide ligand indicating a lowering of symmetry in the anion.

Thermal analysis, X-ray diffraction and infrared spectroscopic study of synthetic brochantite

“…Hence, sample SO is pure brochantite. The infrared spectrum of sample SO closely resembles that of brochantite [ 13,14] and shows all the peaks corresponding to it; it differs markedly as regards the shapes and peak positions oflangite [13,14] antlerite [13][14][15], dolerophanite [11,14], copper hydroxide [16] and copper oxide [17]. Thus, these results confirm that sample SO is pure brochantite.…”

“…H20, where n varies from 2 to 3. In the thermoanalytical studies by Ramamurthy and Secco [11] and Pannetier et al [8-1, brochantite was found to decompose to dolerophanite between 250 and 400 ~ but no formation of antlerite was reported. Vandael and Vanthournhout [18] studied the copper patina obtained in urban atmospheres which mainly consists of brochantite by thermal analysis and reported that antlerite is formed at 280-380 ~ which is converted to dolerophanite between 415 and 550 ~ Brochantite minerals from the Soviet Union [19] also showed the formation of dolerophanite around 530 ~ which finally gave copper oxide around 900 ~ In this study, however, the presence of dolerophanite could not be detected at any stage of the decomposition of brochantite, either by X-ray diffraction or by infrared spectroscopy.…”

Hydrogen bonding in basic copper salts: a spectroscopic study of malachite, Cu2(OH)2CO3, and brochantite, Cu4(OH)6SO4

“…In this paper, we present the results obtained for malachite, Cu2(OH)2CO3(12C and lsC), and brochantite, CHa(OH)6SO 4. On the basis of the available spectroscopic data of brochantite (Secco 1988;Ramamurthy and Secco 1970) a definite assignment of the hydroxide bands is not possible. For Cu2(OH)2CO3, only the wavenumbers of the internal vibrations are known (Ramamurthy and Secco 1970).…”

Ceruleite: infrared spectroscopy and a new locality in Cornwall

“…On this basis alone, hydroxyl ions would be expected to be bound much more firmly to AI 3 § than to Cu 2 § This is borne out by thermal analyses, in which hydroxide bound to copper tends to come offat around 300 ~ whereas at least some of that bound to aluminium may be retained at well over 500~ (Todor, 1976). Hydroxide bound to copper in some basic salts may even be removed well below 250 ~ (Ramamurthy and Secco, 1970), a lower temperature than that of the removal of the last water from hydrated aluminium sulphate (about 400 ~ Todor, 1976). It is therefore possible that water loss from hydroxide bound to copper might take place at a lower temperature than that of some water coordinated to aluminium, and that this might explain the apparent retention of H20 and loss of OH-by 250~ indicated by infrared spectroscopy.…”