Hydrogen Sulfide Method of Analysis

Hydrogen Sulfide Method of Analysis 

a method for the chemical qualitative analysis of mixtures of metal ions, mainly cations, in aqueous solutions. The method is based on the varying solubilities of the chlorides, hydroxides, carbonates, and sulfides of metals.

The hydrogen sulfide method of analysis assumes the classification of metal ions given in Table 1. Other classifications of metal ions also exist. Using the group reagents, which are precipitating agents [HCl, H₂S, (NH₄)₂S, (NH₄)₂CO₃], a complex mixture of metal ions is separated consecutively into five analytical groups.

Systematic analysis involves, as a first step, the addition of HCI, which separates ions of Group V. Cations of Group IV are then precipitated from the filtrate (pH approximately 3) by the introduction of H₂S. Next, cations of Group III are precipitated by the action of an excess of (NH₄)₂S. The mixture of cations of Groups I and II remaining in solution are then separated by the addition of a solution of (NH₄)₂CO₃. Each group of cations is subsequently separated into subgroups, and the ions are identified by chemical reactions.

The hydrogen sulfide method is used for a preliminary identification of a substance of unknown composition in order to select the most efficient method for the substance’s quantitative analysis. Quantitative hydrogen sulfide analysis is sometimes used in the analysis of materials of complex composition.

REFERENCE

Alekseev, V. N. Kurs kachestvennogo khimicheskogo polumikroanaliza, 5th ed. Moscow, 1973.

A. I. BUSEV