Greener Alternative to Qualitative Analysis for Cations without H₂S and Other Sulfur-Containing Compounds

Author Contact: sidhwaniindu@hotmail.com

Summary

Qualitative analysis of inorganic salts and mixtures is a common component of high school, undergraduate, and graduate level curricula. The hydrogen sulfide scheme given by Fresenius is a widely accepted scheme used for studying Le Chatelier's Principle, the common-ion effect, and solubility products. However, H₂S is deadly even at low air concentrations, can cause permanent physiological damage, contributes to air pollution, and can contaminate ground water. Despite these drawbacks, it is relatively easy and cheap to make which it why it is still commonly used.

In this greener experiment, hydrogen sulfide is replaced as a reagent for qualitative analysis experiments with safer chemicals and procedures. A variety of non-toxic cations (K⁺, Ba²⁺, Fe²⁺, Mg²⁺, Pb²⁺, Mn²⁺, Ca²⁺, Cu²⁺, Zn²⁺, Fe³⁺, Zn²⁺, NH⁴⁺, Cu²⁺, Ni²⁺, Zn²⁺) are analyzed using hydroxide, sulfates, chloride, ammonia, etc.

Supplemental information includes a student handout, procedures for all the tests and suggestions on cation combinations for the unknown solutions.

Summary prepared October 2008 by Douglas M. Young at the University of Oregon.

Category Descriptors

Chemistry Concepts

• Qualitative Analysis
• Separation Science
• Solutions/Solvents

Green Chemistry Principles

• Minimize the Potential for Accidents
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Analytical Chemistry
• Inorganic Chemistry

Target Audience

• Colleges/Universities
• Secondary Schools

Source

• Journal Articles