Fatima Akintobi Suphate are prepared in the laboratory or Industry. At the same time, 'sulphides' as such has no meaning in exploration as they occur as compounds like PbS, MgS, FeS, and like. These compounds and the associated minerals can be located using gravimetry as they have more density.

Gravimetric Determination of Sulfate (SO₄²⁻)

Main Takeaway: Quantify sulfate by precipitating it as barium sulfate (BaSO₄), isolating, igniting, and weighing the precipitate; the mass of BaSO₄ yields the sulfate content by stoichiometry.

1. Principle

Under hot, strongly acidic conditions, sulfate ions react with barium ions to form insoluble barium sulfate:

\ceBa2+(aq)+SO42−(aq)−>BaSO4(s)\ceBa2+(aq)+SO42−(aq)−>BaSO4(s)

Complete precipitation, digestion, and proper treatment of the solid ensures accuracy1.

2. Reagents & Apparatus

Reagents

• Barium chloride solution (~0.05–0.25 M), warmed
• Concentrated HCl (to adjust pH ~1–2)
• Distilled hot water
• Dilute H₂SO₄ wash (~0.1 M) Apparatus
• Analytical balance (±0.1 mg)
• Ash-free filter paper (e.g., Whatman No. 42)
• Porcelain crucibles with lids
• Beakers (400 mL) and watch glasses
• Hot plate or steam bath
• Desiccator and muffle furnace

3. Procedure

4. Calculations

Let mBaSO4mBaSO4 = mass of ignited BaSO₄ (g). Molar masses: MSO42−=96.06MSO42−=96.06, MBaSO4=233.39MBaSO4=233.39.

Mass of sulfate:

mSO42−=mBaSO4×96.06233.39mSO42−=mBaSO4×233.3996.06

Percent sulfate (w/w):

% SO42−=mSO42−msample×100%SO42−=msamplemSO42−×100

For aqueous samples, express concentration as mg SO₄²⁻ L⁻¹ by dividing mSO42−mSO42− (mg) by sample volume (L).

5. Critical Considerations

Acid medium promotes crystal growth and suppresses hydroxide formation. Digestion reduces occlusion of impurities and yields larger, more filterable crystals. Hot washes remove soluble salts; acid wash prevents redissolution. Proper ignition removes filter ash without decomposing BaSO₄. Interferences (e.g., silicates, phosphates, heavy metals) may co-precipitate; preliminary treatment (e.g., removal of Fe³⁺) can be required4.

This step‐by‐step protocol ensures reliable quantification of sulfate via gravimetric precipitation as BaSO₄.

Refer To These References

Gravimetry cannot measure minerals or any specific substances directly. It measures gravity acceleration. Gravity acceleration is caused by matter.

Sulphate is matter as well as any other material, liquid and gas (even dark matter...).