# Salt Analysis

> Salt analysis for JEE Chemistry: group separation of cations, confirmatory tests, flame tests and anion tests like the brown ring test.

- Canonical URL: https://prepelephant.com/topics/jee/chemistry/salt-analysis
- Exam / course: JEE · Subject: Chemistry
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Salt Analysis", PrepElephant, https://prepelephant.com/topics/jee/chemistry/salt-analysis

## Direct answer

Qualitative salt analysis identifies the ions in a salt by systematic precipitation. Cations are separated into six groups by adding group reagents in fixed order — dilute HCl, H2S in acid, NH4OH with NH4Cl, H2S in base, ammonium carbonate — each group precipitating while the rest stay dissolved. Anions are tested separately by gas-evolution and precipitation tests, including the brown ring test for nitrate and the chromyl chloride test for chloride.

## What you must remember

- Group I, dilute HCl: Ag+, Pb2+, Hg2^2+ precipitate as chlorides; AgCl dissolves in NH4OH and returns with dilute HNO3.
- Group II, H2S in dilute HCl: Cu2+, Bi3+, Cd2+, Hg2+, As3+, Sb3+, Sn2+ precipitate as acid-insoluble sulphides — the acidic medium keeps S^2- low.
- Group III, NH4OH with NH4Cl buffer: Fe3+, Al3+, Cr3+ precipitate as hydroxides; Fe3+ confirms as Prussian blue Fe4[Fe(CN)6]3 with potassium ferrocyanide.
- Group IV, H2S in ammoniacal medium: Zn2+, Mn2+, Ni2+, Co2+ sulphides precipitate as the basic medium raises S^2-.
- Group V, (NH4)2CO3 with NH4Cl: Ba2+, Sr2+, Ca2+ carbonates; Group VI: Mg2+ with disodium hydrogen phosphate.
- Flame colours: sodium golden yellow, potassium lilac (viewed through blue cobalt glass), calcium brick red, strontium crimson, barium apple green, copper bluish green.
- Brown ring test for nitrate: fresh FeSO4 layered under concentrated H2SO4 forms a brown ring of [Fe(H2O)5NO]SO4.
- Chromyl chloride test for chloride: salt with K2Cr2O7 and concentrated H2SO4 evolves red-brown CrO2Cl2 fumes; lead acetate then gives yellow PbCrO4.
- Anion quick tests: carbonate fizzes with dilute HCl (limewater milky); sulphide blackens lead acetate paper; sulphite's SO2 turns acidified dichromate paper green; bromide colours the organic layer orange-brown with chlorine water; iodide violet; sulphate gives BaSO4 insoluble in concentrated HCl; phosphate with ammonium molybdate gives canary yellow.

## Common confusion

The recurring confusion is why one reagent (H2S) precipitates Group II but not Group IV: in acid, H+ suppresses S^2- so only the least soluble sulphides drop; making the medium basic floods S^2- and precipitates the rest. Students likewise miss why NH4Cl precedes NH4OH — the buffer keeps OH- low so Group IV hydroxides do not precipitate prematurely. In anion tests, the trap is specificity: a BaCl2 precipitate must survive concentrated HCl before it counts as sulphate.

## Exam-focused takeaway

JEE Main frames salt analysis as single-line recall: match ion with confirmatory test, precipitate colour or flame. JEE Advanced (steady weight through the practical-chemistry portion) prefers sequence and reasoning — which ions remain in the filtrate after a step, why a reagent's medium matters, balanced equations for the brown ring and chromyl chloride tests. Learn the scheme as a flow diagram you can redraw; disjointed facts fail exactly when the paper asks for the next step.

## Frequently asked questions

### Why is H2S passed in acidic medium for Group II?

Acid suppresses S^2- through the common ion effect, so only the least soluble sulphides precipitate, leaving the rest for later groups.

### Why is NH4Cl added before NH4OH in Group III?

It buffers OH- low, so only the very insoluble hydroxides (Fe3+, Al3+, Cr3+) precipitate while others remain dissolved.

### What is the brown ring test?

For nitrates: FeSO4 solution with the sample, layered under concentrated H2SO4, forms a brown ring of [Fe(H2O)5NO]SO4 at the junction.

### What does the chromyl chloride test detect?

Chloride: heating with K2Cr2O7 and concentrated H2SO4 evolves red CrO2Cl2 fumes — a response chromates and sulphates cannot duplicate.

### Why is potassium viewed through blue cobalt glass?

The glass absorbs sodium's golden yellow flame, which would otherwise mask potassium's delicate lilac.

### Which carbonates precipitate in Group V, and how are they separated?

Ba2+, Sr2+ and Ca2+ with ammonium carbonate; differential solubility of their chromates and sulphates separates them from barium to calcium.