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The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 17
(2012) pp 152-156
DOI 10.1007/s00897122433
Analysis of Ascorbic Acid in Supplement Tablets from the Mole Ratios of the Electrolytic Products: An Experiment for the Undergraduate Laboratory
Rajeev B Dabke*, Zewdu Gebeyehu, and Nicole Ippolito
Department of Chemistry, Columbus State University,
Columbus, GA 31907, dabke_rajeev@columbusstate.edu
Received January 28, 2012. Accepted May 16, 2012.
Published: 10 August 2012
Abstract. A unique undergraduate experiment for the quantitative analysis of ascorbic acid in dietary supplement tablets is presented. The experiment combines titration concept with electrolysis and the gas laws. Powdered supplement tablet sample is placed in the anode compartment of the electrolysis cell containing potassium iodide. Electrolytically generated I2(aq) oxidized the ascorbic acid in the sample. Starch is used as a visual indicator. The volume of H2(g) produced at the cathode is monitored and the amount of I2(aq) produced at the anode is determined from the volume of H2(g) produced at the cathode. The amount of ascorbic acid present in the sample is determined from the mole relationships between I2(aq) and H2(g). The experimentally determined amount of ascorbic acid from the electrolytic titration method agrees with the volumetric titration results and the manufacturer’s label. Preparation of an electrolysis cell, experimental procedure, and results of the electrolytic titration are presented.
Key Words: Laboratories and Demonstrations; quantitative analysis
(*) Corresponding author. (E-mail: dabke_rajeev@columbusstate.edu)
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