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In the Laboratory
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A Low-Cost Device for Automatic Photometric Titrations
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Fábio R. P. Rocha
Departamento de Quí, Universidade Federal de São Carlos, São Carlos, Brazil
Boaventura F. Reis
Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, PO Box 96, 13400-970 Piracicaba, SP, Brazil
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February 2000
Vol. 77 No. 2
p. 258
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| Abstract |
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Electronics is an important topic in chemistry courses. However, the introduction of basic concepts is often difficult and the lab instruments are frequently seen as "black boxes". To address this problem, we propose the construction of a simple, low-cost (about $150 U.S.) automatic photometric titrator employing a light-emitting diode (LED) and a phototransistor. The electronic circuit can be assembled by the students themselves. The device was employed to implement a common procedure in chemical labs, making feasible the introduction of concepts related to electronics in undergraduate chemistry courses. The titrator is able to work automatically, since a feedback system permits stopping the addition of titrant solution when the end-point is achieved. With this demonstration, it can be stressed that automatic procedures can be implemented without expensive instruments. Additionally, a classical procedure becomes more attractive to the students and its importance to chemical analysis can be emphasized. The feasibility of the titrator was demonstrated by acid-base titrations of HCl solutions with NaOH in the presence of phenolphthalein and by iodimetric determination of ascorbic acid in vitamin C tablets and lemon juice. Precise results (0.7% relative standard deviation, n = 10) in agreement at the 95% confidence level with those attained by a conventional procedure were obtained.
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| More Information |
 Citation |
Rocha, Fábio R. P.; Reis, Boaventura F. J. Chem. Educ. 2000 77 258.
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Keywords |
Instrumental Methods; Analytical Chemistry; Quantitative Analysis; automation; Titrimetry; Ascorbic acid
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History |
Created:
Last Updated: |
January 5, 2000
April 15, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
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February
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258
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