Thermochimica Acta 322 (1998) 83±88
A thermal analysis study of some transition-metal dithizonates
M. Chahud, M.A.S. Carvalho Filho, N.S. Fernandes, J. Zuanon Netto, M. Ionashiro*
Â
Instituto de Quõmica, UNESP, Araraquara, C.P. 355 CEP, 14801-970, SaÄo Paulo, Brazil
Received 11 March 1998; received in revised form 1 July 1998; accepted 2 July 1998
Abstract
Solid dithizonates of Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II), have been prepared. Thermogravimetry (TG),
derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and elemental
analysis have been used to characterize and study the thermal stability and thermal decomposition of these compounds.
# 1998 Elsevier Science B.V.
Keywords: Transition metal; Dithizonate; Thermal decomposition
1. Introduction
mogravimetric studies of silver, lead, zinc and copper
dithizonates and the TG curves recorded in a Cheve-
nard thermobalance showed explosive decomposition
for these compounds. No reference has been found to
the application of TG and DSC in the study of iron(II),
cobalt(II), nickel(II) and cadmium(II) dithizonates.
In this study, bivalent iron, cobalt, nickel, copper,
zinc, cadmium and lead dithizonates are prepared and
investigated by complexometry, TG, DTG, DSC and
X-ray diffraction powder patterns.
The aqueous solution chemistry of dithizone
(diphenylthiocarbazone) has been extensively studied
since the introduction of these compounds as a reagent
for the determination of heavy metals. Studies of the
solid-state compounds have been reported by Harding
[1], who derived the crystal structure of the mercury
dithizone complex by X-ray diffraction. Bryan and
Knoff [2] reported the preliminary results of an X-ray
diffraction study of keto cupric dithizonate. The struc-
ture of keto nickel dithizonate was determined from
three-dimensional single crystal X-ray data by Laing
and Sommerville [3]. Mawby and Irving [4] described
the crystal structure of keto zinc(II) dithizonate and its
relevance to the stabilities of its o- and p-methyl
derivatives. Dyfverman [5] described the infrared
spectra of a number of metal dithizonates. Pariaud
and Archinard [6] reported the preparation and ther-
2. Experimental
Aqueous solutions of the metal were prepared by
dissolving the chloride (Co), nitrate (Cd, Pb) or sul-
phate (Fe, Cu, Ni, Zn). The solid state complexes were
prepared by mixing solutions of the corresponding
metal ions in excess with a dithizone solution of
0.05% (w/v) in ketone, to effect total precipitation
of metal dithizonate. The precipitates were washed
with distilled water to eliminate chloride, nitrate or
*Corresponding author.
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