User`s manual

62 Chapter 6: Sample Experiments
Calorimetry Sciences Corp.
CSC 5300 N-ITC III 63
User’s Manual
and click the burette up icon to initialize
the plunger position.) Insert the syringe and
burette drive into the N-ITC III as shown in
Figure 6-3.
Turn on the stirrer at 150 rpm, allow the sys-
tem to re-equilibrate until the heat reading on
the calorimeter is stable, and then begin the
experiment. Enter a le name for the data at
the prompt.
Results
The results should be similar
to those shown in Figure 6-4.
Note that each peak has the
same area except for the rst.
Typically the rst injection
shows less heat than expected.
This is often due to diffusion
across the tip of the needle or
to difculties in positioning
the burette drive. For 5 μL
injections of 1.00 mM HCl at
25°C, the expected heat is 237
μJ. The protonation enthalpy
in J/mol at any temperature
between 5 and 50°C is given
as:
2
nprotonatio 0.59275t -102.28t 49659- H +=∆
Equation 6-1
Figure 6-3: Inserting the burette drive into the
N-ITC III.
Figure 6-4: Typical calibration graph – Protonation of Tris
base. The last injection peak in the gure is smaller because
the titrant in the syringe was consumed.