Open AccessEnthalpies of solution of nucleic acid bases. 1. Adenine in water
Author(s) -
Marthada V. Kilday
Publication year - 1978
Publication title -
journal of research of the national bureau of standards
Language(s) - English
Resource type - Journals
eISSN - 2376-5259
pISSN - 0160-1741
DOI - 10.6028/jres.083.023
Subject(s) - enthalpy , dilution , chemistry , calorimeter (particle physics) , adiabatic process , thermodynamics , enthalpy change of solution , calorimetry , heat capacity , standard molar entropy , analytical chemistry (journal) , chromatography , physics , optics , detector
An adiabatic solution calorimeter was used to measure the enthalpy of solution in water of various adenine samples for which a large amount of analytical information is reported. The experimental imprecision of the measurements was 1.1 percent. However, it was necessary to assign an overall uncertainty of 3 percent because of impurity uncertainties. Thus, the best value for the enthalpy of solution is Δ H ∘ ( ∞ , 298.15 K ) = ( 33.47 ± 1.00 ) k J m o l - 1Δ C p = (78.7 ± 10.4) J·mol -1 ·K -1 in the range 298 to 328 K at 5 mmol·kg -1 , and the enthalpy of dilution is -(316 ± 208) kJ·mol -1 (mol·kg -1 ) -1 in the range 1 to 7 mmol·kg -1 . The entropy of solution for adenine was calculated to be Δ S° (298.15 K) = (72.1 ± 3.9) J·mol -1 ·K -1 , and the partial molar heat capacity at infinite dilution, C° p 2 = (226 ± 11) J ·mol -1 ·K -1 . The density of adenine was measured by displacement as 1.47 g·mL -1 with an estimated uncertainty of 1 percent.