Adiabatic calorimetry

The pair of insulated vessels in Fig. 11.21 are equipped with, in addition to temperature measuring devices (thermocouples, not thermometers as shown), provisions for heating or cooling the contents. The vessel (or cell) on the left contains a reference aqueous solution, meaning one without the reactive substance that is dissolved in the right-hand cell. The system can be operated in either of two modes.

Titration mode

In the first mode, reactant is periodically injected into the right-hand cell and, at a constant cooling rate, the AT between the left and right cells is recorded. As seen in Fig. 11.21, the temperature spikes at each reactant injection (if the reaction is exothermic), and returns to the base temperature by the continuous cooling. Each temperature pulse represents the heat evolved by partial uptake of the injected reactant (often a ligand) by the reactant in the vessel (a macromolecule). As the number of injections increases, the reaction sites on the macromolecule become saturated, and the height of the spikes decreases and eventually vanishes.

What follows is a theoretical model of the "data" shown in Fig. 11.22. For this analysis, the conditions of the experiment are assumed and the thermodynamic properties of the ligand binding reaction with the sites on the macromolecule are calculated. For the purposes of illustrating the method, the simplest system consisting of identical and independent binding sites analyzed in Sect. 11.6.1 is treated.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

Get My Free Ebook


Post a comment