Systematic Errors in an Isoperibol Solution Calorimeter Measured with Standard Reference Reactions

Area of Science:

• Thermochemistry
• Calorimetry
• Physical Chemistry

Background:

• Isoperibol calorimeters are widely used for thermochemical measurements.
• Accurate heat leak corrections are crucial for precise enthalpy of solution determination.
• Previous studies have not fully addressed systematic errors in common calorimetric procedures.

Purpose of the Study:

• To identify and quantify systematic errors in a widely-used isoperibol calorimeter design.
• To investigate the impact of stirring and heat leak correction procedures on measurement accuracy.
• To recommend improved calorimetric procedures for accurate thermochemical data.

Main Methods:

• Utilized an isoperibol calorimeter to measure the enthalpy of solution for SRM 1655 (KCl) in water.
• Analyzed heat leak corrections, focusing on the effects of stirring.
• Investigated systematic errors in the enthalpy of solution measurements for tris(hydroxymethyl)aminomethane in aqueous HCl.

Main Results:

• Identified systematic errors of approximately 0.5% in the endothermic enthalpy of solution of KCl.
• Attributed these errors to inadequate stirring and common heat leak correction methods.
• Detected other systematic errors in the exothermic enthalpy of solution measurements of tris(hydroxymethyl)aminomethane.

Conclusions:

• Common calorimetric procedures and inadequate stirring lead to significant systematic errors in heat leak corrections.
• Revisions to stirring and heat leak correction protocols are necessary for accurate thermochemical measurements.
• Recommended procedures are summarized to improve the reliability of calorimetric data.