Testing of the Calorimeter

All enthalpy of solution measurements were carried out with an LKB 8700-1 precision calorimetry system. The experimental procedure and tests of the calorimeter have been reported previously (3, 4, 5). The purification of the solvent DMF (Baker Analyzed Reagent) and of all solutes used has been described in the same papers. The solvent mixtures were prepared by weighing and the mole fraction of water in the DMF-water mixtures was corrected for the original water content of the amide as measured by Karl Fischer titration. 

This work was supported in part by a grant (GB18017) from the Division of Molecular Biology, National Science Foundation. We acknowledge the technical assistance of Mr Ross Hardison and Mr Shawn Jones for the testing of the calorimeter and the collection of some of the data. 

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