Journal of Thermal Analysis and Calorimetry, Vol. 74 (2003) 497–502
THE THERMAL TRANSFORMATIONS IN
Zn(NO
3
)
2
–H
2
O (1:6) SYSTEM
A. J. Kozak
1
, Krystyna Wieczorek-Ciurowa
1*
and A. Kozak
2
1
Institute of Inorganic Chemistry and Technology, Cracow University of Technology, 24,
Warszawska, 31-155 Cracow, Poland
2
Institute of Building Materials and Structures, Cracow University of Technology, 24,
Warszawska, 31-155 Cracow, Poland
Abstract
Using thermal analysis as well as isothermal gravimetric measurements, the thermal stability of the
zinc nitrate(V) hexahydrate has been determined. Some intermediate products are the results of
melting, evaporation, hydrolysis, polycondensation and decomposition processes occurring in the
salt – water system up to 300°C. Solid phases were characterized by means of chemical analyses and
X-ray powder diffraction method.
Keywords: decomposition, dehydration, hydrates, hydrolysis, isothermal gravimetry, melting,
polycondensation, thermal analysis, zinc nitrate(V)
Introduction
Crystalline hydrated salts are a numerous group of inorganic compounds. Knowledge
of their thermal stability is the essential phenomenon in the field of solid-state chem-
istry. There is a strong connection between the thermal stability and the reactivity of a
given substance, e.g. [13].
Visual observations of the crystallohydrates during their heating can provide us
with valuable information. Knowledge of solubility of anhydrous salts is also impor-
tant for proper interpretation of the results of thermal decomposition of hydrated salts
while the results of the analysis of gaseous products of the decomposition using e.g.
TG-MS, TG-FTIR methods are always very useful.
This paper presents an attempt of a more complete interpretation of the phenom-
ena occurring during heating of inorganic crystallohydrates exemplified by the zinc
nitrate(V) hexahydrate, Zn(NO
3
)
2
·6H
2
O.
The thermal stability of hydrated zinc nitrate has aroused interest of many research-
ers not excluding ourselves [4–9]. Although there are a lot of papers concerning thermal
changes of the hydrates, the results are usually fragmentary, incoherent and even false.
This probably results from different types of water bound in salt structure (from weak ad-
sorption of water molecules to molecules which are strongly bound chemically) and the
1388–6150/2003/ $ 20.00
© 2003 Akadémiai Kiadó, Budapest
Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht
* Author for correspondence: E–mail: kwc@usk.pk.edu.pl