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Gravimetric Estimation of Barium as Barium Sulphate

1. Aim

To estimate barium in an assigned soluble barium sample by isolating and weighing barium sulphate. Record the original sample form and aliquot factor here.

2. Requirements

Assigned barium-containing sample, verified sulphate precipitant and acidic medium, water, beakers, stirring rod, filter apparatus, ashless paper or approved crucible, drying or ignition equipment, desiccator, analytical balance, and barium waste stream. Exact volumes, temperatures, and drying or ignition conditions are specified in your college lab manual and instructor's method sheet.

3. Theory

Barium ion forms sparingly soluble barium sulphate. With complete precipitation, quantitative transfer, washing, and constant mass, the precipitate mass gives barium mass through the gravimetric factor 137.33/233.39 using current rounded atomic weights. Entrained impurities raise the measured mass; transfer loss, incomplete precipitation, or dissolving the precipitate lowers it. The mass result belongs to the aliquot until dilution is applied.

4. Procedure

1. Confirm the soluble barium source, total dilution, aliquot, precipitant, and gravimetric collection method; obtain missing specifications from the approved local method.
2. Weigh the clean dry crucible or filter assembly according to the validated method.
3. Transfer the verified aliquot and add the prescribed acidic medium; heat and add sulphate precipitant in the controlled order.
4. Allow the precipitate to digest, then test for complete precipitation as directed.
5. Filter and wash without losing solid. Dry or ignite using the method-approved conditions, cool in a desiccator, and weigh.
6. Repeat heat, cool, and weigh to the method-defined constant mass. Subtract tare and apply the barium factor and aliquot factor.

5. Calculation, graph, or images as appropriate

Assumed values for practice only: assumed empty crucible mass 25.0000 g and assumed final constant mass 25.1000 g. These invented masses are not observations.

1. Assumed barium sulphate precipitate mass = 25.1000 minus 25.0000 = 0.1000 g.
2. The barium mass fraction in BaSO4 is 137.33 ÷ 233.39 = 0.5884, rounded.
3. Illustrative barium mass in the assumed aliquot = 0.1000 × 0.5884 = 0.05884 g.
4. Whole-sample result must be recorded here until the actual weighed masses and aliquot factor are known.

6. Result

Record the actual result here only when the stated conditions and observations are confirmed. The monograph decision is made by the qualified reviewer against the assigned current monograph or approved method and recorded in the student record. This page decides nothing: it does not pass, fail, identify, or release any sample. Safety note: Soluble barium reagents are toxic; hot acidic liquids and crucibles cause burns. Use supervised handling, tongs, eye protection, and a dedicated barium waste stream.

7. References

1. Pharmacy Council of India, Pharm.D. Regulations, 2008.
2. Amrita Virtual Labs, Gravimetric Estimation of Barium.
3. Karnatak University, Chemistry Laboratory Manual.

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