JCE Online Journal of Chemical Education
 | Subscriptions  | Software Orders  | Support  | Contributors  | Advertisers  | 

JCE Print
   Current Issue
 Previous Issues
 Supplements
 Search JCE Index

JCE Digital Library
   DigiDemos
 QBank
 SymMath
 WebWare

JCE Software
   Latest Releases
 Software & Video
 Downloads
 Support

Only@JCE Online
   JCE Online Store
 JCE HS CLIC
 JCE Discussion Forums
   Biographical Snapshots
 ChemEd Resource Shelf
 Featured Molecules
 Hal's Picks
 Project Chemlab
 Reviewed WWW Sites
 "Web-Ed" Articles

About JCE
   Features
 Publications
 Operations
 Outreach
 Contact Us


  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > June  >
In the Laboratory
Simultaneous Determination of the Ionization Constant and the Solubility of Sparingly Soluble Drug Substances. A Physical Chemistry Experiment
Andria Aroti and Epameinondas Leontidis
Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
Cover
June 2001
Vol. 78 No. 6
p. 786
Abstract
We examine the use of the inverse titration method for determining the ionization constant of weak organic bases when the basic form of the substance is highly insoluble in aqueous solutions. The inverse titration involves progressive dissolution of the precipitate of the insoluble basic form through addition of a strong acid, and determination of the total solubility at each step with a suitable analytical technique. Analysis of the experimental data allows the simultaneous determination of the ionization constant and the solubility of the basic form. We use dibucaine, a local anaesthetic, and analyze its total solubility after each acid addition using UV spectrophotometry. This simple experiment allows the accurate determination of the pKa of the compound at various temperatures, but provides only a rough estimate of the solubility of the basic form.
Supplement
The full text of this paper is available and provides more extensive background and theoretical material, further information on safety and waste disposal and alternatives to use of dibucaine, details of the data analysis, and an expanded discussion.
*  Contents JCE2001p0786W.doc (Microsoft Word)
*  Download
JCE2001p0786W.sit

JCE2001p0786W.zip
More Information
*  Citation
 Aroti, Andria; Leontidis, Epameinondas. J. Chem. Educ. 2001 78 786.
*  Keywords
 Acid-Base Chemistry; Aqueous Solution Chemistry; Drugs / Pharmaceuticals; Electrochemistry; Equilibrium; Physical Chemistry; Laboratory Instruction
*  History
 Created:
Last Updated:		 May 8, 2001
August 31, 2005
<< Previous Article Table of Contents Next Article >>
  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > June  > Page 786


Subscriptions
 Subscription Info
 Order Forms

JCE HS CLIC

Our Secondary School editors work hard to distill all the JCE materials to produce a fraction of particular interest to high school teachers. We call it CLIC.
 JCE HS CLIC

Contributions Welcome
JCE welcomes your submission
 Contributors' Corner

Advertisers
In recent years we have worked hard to better match our advertisers with our readers. When shopping for chemistry education materials, visit our advertisers' WWW sites first.
 Recent Advertisers

Be An Ambassador
Take JCE along on your outreach missions. Copies of the Journal, guest access to JCE Online, our publications catalog, and more are available for your participants.
 Outreach with JCE

Comments to
jceonline@chem.wisc.edu		 Copyright © Division of Chemical Education, Inc., American Chemical Society.
All rights reserved.