ABSTRACT

For the first time high-temperature polymorphic transition of ammonium sulfate (NH4)2SO4 (Tpt 370 C) was experimentally recorded and characterized by differential scanning calorimetry. Phase transitions parameters of (NH4)2SO4, of ammonium bisulfate NH4HSO4, of triammonium hydrogen disulfate (NH4)3H(SO4)2 and of ammonium sulfamate NH4SO3NH2 were clarified. Method of determining the phase transitions parameters for thermally unstable substances, in particular for the triammonium hydrogen disulfate (NH4)3H(SO4)2, was developed and tested with the help of differential scanning calorimetry.

Compounds

#	Formula	Name
1	H5NO4S	ammonium acid sulfate
2	H13N3O8S2	triammonium hydrogen disulfate
3	H6N2O3S	ammonium sulfamate
4	H8N2O4S	ammonium sulfate

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Phase	Method	#Points
POMD	1	Normal melting temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	1	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	2	Triple point temperature, K ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	2	Normal melting temperature, K ; Crystal 1		Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1		Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	3	Normal melting temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 3		Crystal 3 Crystal 2 Air at 1 atmosphere	DSC	1
POMD	4	Solid-liquid equilibrium temperature, K ; Crystal 2	Pressure, kPa; Crystal 2	Crystal 2 Crystal 1	DTA	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2	Temperature, K; Crystal 2	Crystal 2 Crystal 1	DSC	1

Thermodynamics Research Center / ThermoML | Thermochimica Acta

Phase transitions of some sulfur-containing ammonium salts

Kosova, D. A.[Darya A.], Emelina, A. L.[Anna L.], Bykov, M. A.[Mikhail A.]

ABSTRACT