Inorganic Salt Analysis – Systematic Procedure (Class 11-12 CBSE)

Introduction

Inorganic salt analysis involves the systematic identification of cations (basic radicals) and anions (acid radicals) present in a given salt sample. The following is a step-by-step procedure commonly followed in CBSE curriculum for qualitative inorganic analysis.

Systematic Procedure for Salt Analysis

1. Preliminary Examination
   • Physical appearance (color, texture, crystalline nature)
   • Solubility in water (soluble or insoluble)
   • Odor (if any)
   • Flame test (to detect certain metal cations)
2. Preparation of Solution
   • Dissolve a small amount of salt in distilled water (if soluble)
   • Filter to remove insoluble impurities
3. Detection of Cations (Basic Radicals) by Group Separation

   Cations are classified into six groups based on their precipitation behavior with specific reagents:

   Group	Group Precipitate	Main Group Reagent	Cations in Group	General Method
   Group I	Chlorides (white ppt.)	Dilute HCl	Ag⁺, Pb²⁺, Hg₂²⁺	Precipitated as chlorides
   Group II	Sulphides (coloured ppts.)	H₂S in dilute acid	Cu²⁺, Bi³⁺, Cd²⁺, As³⁺, Sb³⁺, Sn²⁺, Pb²⁺, Hg²⁺	Precipitated as sulphides
   Group III	Hydroxides (coloured ppts.)	NH₄OH + NH₄Cl	Fe³⁺, Al³⁺, Cr³⁺	Precipitated as hydroxides
   Group IV	Sulphides (in ammoniacal medium)	H₂S in NH₄OH medium	Zn²⁺, Co²⁺, Ni²⁺, Mn²⁺	Precipitated as sulphides
   Group V	Carbonates (white ppt.)	(NH₄)₂CO₃ + NH₄Cl + NH₄OH	Ba²⁺, Sr²⁺, Ca²⁺	Precipitated as carbonates
   Group VI	None (soluble cations)	None	Mg²⁺, Na⁺, K⁺, NH₄⁺	Detected by special tests

4. Confirmatory Tests for Cations

   Perform specific confirmatory tests for each cation suspected, based on group separation results. Examples include flame tests, precipitation with specific reagents, and color changes.

5. Detection of Anions (Acid Radicals)

   Test the filtrate remaining after cation group precipitations for common anions such as chloride, sulphate, nitrate, carbonate, bicarbonate, phosphate, etc., using standard qualitative tests:

   • Test for chloride: Silver nitrate test (white ppt.)
   • Test for sulphate: Barium chloride test (white ppt.)
   • Test for nitrate: Brown ring test
   • Test for carbonate/bicarbonate: Effervescence with dilute acid
   • Test for phosphate: Ammonium molybdate test
6. Recording Observations and Conclusion

   Document all observations such as color, precipitate formation, solubility, and confirmatory test results.

   Identify the cations and anions present in the salt sample.

Important Points

• Always carry out tests in the specified order to avoid cross-interference.
• Wash all precipitates thoroughly between steps to remove impurities.
• Use freshly prepared reagents for reliable test results.
• Observe colors carefully; many ions have characteristic colors.
• Practice careful handling of acids and reagents with appropriate safety.