Excess enthalpies of aqueous solutions of biuret at 25 °C. Interaction with urea

Abstract

The heats of dilution in water of biuret and the heats of mixing of biuret with urea have been determined by flow microcalorimetry at 25 °C. The excess enthalpies obtained from the experimental data can be expressed as virial expansions of the molalities.The value of the cross interaction coefficient hUB is compared to that calculated through the empirical relation hUB2 = (hUUhBB). The agreement between the two values outlines the strict analogy in the behaviour of these two solutes. The cited combining rule, verified up to now for pairs of solutes having both hii, hjj > 0, is here applied for the first time to a pair having hii, hjj < 0.