ABSTRACT

Apparent molar volumes V(phi) and apparent molar heat capacities Cp(phi) were determined for aqueous solutions of urea, 1,1-dimethylurea, and N,N'-dimethylurea. Measurements were made at molalities m = (0.02 to 6.0) mol*kg-1 for urea, at m = (0.01 to 1.6) mol*kg-1 for 1,1-dimethylurea, and at m = (0.01 to 8.0) mol*kg-1 for N,N'-dimethylurea. Experimental temperatures ranged from (278.15 to 318.15) K for both urea and 1,1-dimethylurea, and from (278.15 to 348.15) K for N,N'-dimethylurea. All measurements were conducted at the pressure p = 0.35 MPa. Density measurements obtained with a vibrating-tube densimeter were used to calculate V(phi) values. Heat capacity measurements obtained with a twin fixed-cell differential temperature-scanning calorimeter were used to calculate Cp(phi) values. Functions of m and T were fitted to the results and were compared with the literature values. The ''structure making/structure breaking'' aspects of urea in water are discussed. Comparisons are made between the different urea compounds, and the effects of the methyl-group additions are outlined.

Compounds

#	Formula	Name
1	CH4N2O	urea
2	C3H8N2O	N,N-dimethylurea
3	C3H8N2O	1,3-dimethylurea
4	H2O	water

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	Constraint	Phase	Method	#Points
POMD	1 4	Apparent molar heat capacity, J/K/mol ; Liquid	Molality, mol/kg - 1; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Extra sensitive DSC	99
POMD	1 4	Apparent molar volume, m3/mol ; Liquid	Molality, mol/kg - 1; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Calculated with densities of this investigation	72
POMD	1 4	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 1; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	VIBTUB:UFactor:4	72
POMD	2 4	Apparent molar heat capacity, J/K/mol ; Liquid	Molality, mol/kg - 2; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Extra sensitive DSC	99
POMD	2 4	Apparent molar volume, m3/mol ; Liquid	Molality, mol/kg - 2; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Calculated with densities of this investigation	72
POMD	2 4	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 2; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	VIBTUB:UFactor:4	72
POMD	3 4	Apparent molar heat capacity, J/K/mol ; Liquid	Molality, mol/kg - 3; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Extra sensitive DSC	225
POMD	3 4	Apparent molar volume, m3/mol ; Liquid	Molality, mol/kg - 3; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Calculated with densities of this investigation	117
POMD	3 4	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 3; Liquid Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	VIBTUB:UFactor:4	117

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Apparent molar volumes and apparent molar heat capacities of aqueous urea, 1,1-dimethylurea, and N,N'-dimethylurea at temperatures from (278.15 to 348.15) K and at the pressure 0.35 MPa

Brown, B. R., Gould, M. E., Ziemer, S. P.[S P], Niederhauser, T. L., Woolley, E. M.[Earl M.]

ABSTRACT