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  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > December  >
In the Laboratory
The Microscale Laboratory
Determination of Acidity Constants by Gradient Flow-Injection Titration
António C. L. Conceição
Centro de Química Estrutural, Complexo Interdisciplinar, Instituto Superior Técnico, 1049-001 Lisboa, Portugal

Manuel E. Minas da Piedade
Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal

Cover
December 2006
Vol. 83 No. 12
p. 1853

Abstract
The use of the gradient chamber flow-injection titration method (GCFIT) to determine acidity constants is illustrated through an experiment involving acetic and benzoic acids. The procedure relies on spectrophotometric detection and on the use of an acid–base indicator to obtain the relation between the pH and the absorbance of the solution throughout the titration. This constitutes a new approach to the determination of pKas by GCFIT. The experiment, which has been designed for an advanced undergraduate course in instrumental analysis, also serves to demonstrate the implementation of automated analytical procedures at the microscale level and a rigorous analysis of an acid–base titration.
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List of chemicals, details of the apparatus and experimental procedure, details of the data treatment and underlying theory, and notes for the instructor are available.
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Citation
Conceição, António C. L.; Minas da Piedade, Manuel E. J. Chem. Educ. 2006 83 1853.
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Keywords
Acids / Bases; Analytical Chemistry; Equilibrium; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Instruction; Microscale Lab; pH; Problem Solving / Decision Making; Quantitative Analysis; Titration / Volumetric Analysis; Upper-Division Undergraduate; UV-Vis Spectroscopy
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History
Created:
Last Updated:
10/30/2006
11/7/2006
 Caution! 
Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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