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Flow Injection as a Teaching Tool for Gravimetric Analysis

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Raquel P. Sartini , Elias A. G. Zagatto and Cláudio C. Oliveira

Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Box 96, Piracicaba SP 13400-970, Brazil

J. Chem. Educ., 2000, 77 (6), p 735

DOI: 10.1021/ed077p735

Publication Date (Web): June 1, 2000

Section:

History, Education, and Documentation

Abstract

A flow-injection system to carry out gravimetric analysis is presented. Students are faced with an instrumental approach for gravimetric procedures. Crucibles, muffle furnaces, and desiccators are not required. A flowing suspension is established by simultaneously injecting an aqueous sample and a precipitating reagent into two merging carrier streams. The precipitate is accumulated on a minifilter hanging under the plate of an analytical balance and is weighed inside the main stream. Since Archimedes' principle holds, a drying step is not needed. After measurement, the precipitate is dissolved and disposed of. As an application, the determination of phosphate based on precipitation with ammonium and magnesium ions in slightly alkaline medium is chosen.

The proposed system is very stable and well suited for demonstration. When applied to analysis of fertilizer extracts with 0.10-1.00% w/v P, it yields precise results (RSD < 0.042) in agreement with an official spectrophotometric method.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Analytical Chemistry

Keywords (Feature):

Topics in Chemical Instrumentation

Keywords (Subject):

Quantitative Analysis

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Citing Articles

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This article has been cited by 3 ACS Journal articles (3 most recent appear below).

Determination of Acidity Constants by Gradient Flow-Injection Titration
Manuel E. Minas da Piedade , António C. L. Conceição
Journal of Chemical Education2006 83 (12), 1853
- Determination of Acidity Constants by Gradient Flow-Injection Titration
  Manuel E. Minas da Piedade , António C. L. Conceição
  Journal of Chemical Education2006 83 (12), 1853
  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–...
  Abstract | Hi-Res PDF | PDF w/ Links
Determination of Hypochlorite in Bleaching Products with Flower Extracts To Demonstrate the Principles of Flow Injection Analysis
Luiz Antônio Ramos , Kátia Roberta Prieto , Éder Tadeu Gomes Cavalheiro and Carla Cristina Schmitt Cavalheiro
Journal of Chemical Education2005 82 (12), 1815
- Determination of Hypochlorite in Bleaching Products with Flower Extracts To Demonstrate the Principles of Flow Injection Analysis
  Luiz Antônio Ramos , Kátia Roberta Prieto , Éder Tadeu Gomes Cavalheiro and Carla Cristina Schmitt Cavalheiro
  Journal of Chemical Education2005 82 (12), 1815
  The use of crude flower extracts is proposed to teach the principles of flow injection procedures. In this experiment a bleaching reaction between hypochlorite and the anthocyanins contained in the flower extracts is examined. The bleaching of the crude ...
  Abstract | Hi-Res PDF | PDF w/ Links
FIA-Spectrophotometric Method for Determination of Nitrite in Meat Products: An Experiment Exploring Color Reduction of an Azo-Compound
José C. Penteado , Lúcio Angnes and Jorge C. Masini , Paulo C. C. Oliveira
Journal of Chemical Education2005 82 (7), 1074
- FIA-Spectrophotometric Method for Determination of Nitrite in Meat Products: An Experiment Exploring Color Reduction of an Azo-Compound
  José C. Penteado , Lúcio Angnes and Jorge C. Masini , Paulo C. C. Oliveira
  Journal of Chemical Education2005 82 (7), 1074
  This article describes the reaction between nitrite and safranine O. This sensitive reaction is based on the disappearance of color of the reddish-orange azo dye, allowing the determination of nitrite at the mg mL–1 level. A factorial optimization of ...
  Abstract | Hi-Res PDF | PDF w/ Links