Verification of Boyle's Law of Ideal Gases
What you will learn
Verify Boyle's Law (P × V = constant) at constant ambient room temperature using a Quill tube / Boyle's Law J-tube apparatus containing an enclosed dry air column.
Materials needed
- Boyle's Law Apparatus (Quill tube / graduated closed burette with mercury reservoir)What is it?Boyle's Law Apparatus (Quill tube / graduated closed burette with mercury reservoir)₹50
Heavy cast-iron frame Boyle's Law apparatus with precision graduated glass tubes and mercury reservoir.
Specifications- Closed Tube
- Graduated 0 – 30 cm, uniform precision bore
- Open Tube
- Parallel vertical tube open to atmosphere
- Base Scale
- Silvered brass meter scale, 1 mm divisions
- Mercury Capacity
- Approx 150 mL triple-distilled
- Fortin's Barometer (to record atmospheric pressure H in cm of Hg)What is it?Fortin's Barometer (to record atmospheric pressure H in cm of Hg)₹95
Fortin's mercurial laboratory barometer for true local atmospheric pressure reference.
Specifications- Range
- 650 – 800 mm Hg
- Vernier Least Count
- 0.1 mm Hg
- Casing
- Enamelled brass tube with glass window
- Cistern
- Flexible leather bottom with ivory pointer
- Pure clean Mercury (in closed apparatus)What is it?Pure clean Mercury (in closed apparatus)₹140
Neoprene high-pressure flexible connecting tube with stainless steel hose clamps.
Specifications- Internal Diameter
- 6.0 mm
- Wall Thickness
- 2.5 mm heavy wall
- Burst Pressure
- 5 bar proof
- Fluid Compatibility
- Chemically inert to liquid mercury
- Laboratory Thermometer (0-100°C)What is it?Laboratory Thermometer (0-100°C)₹185
Standard laboratory apparatus used in Verification of Boyle's Law of Ideal Gases.
Specifications- Category
- Physics Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Vertical Metric Scale & Plumb lineWhat is it?Vertical Metric Scale & Plumb line₹230
Standard laboratory apparatus used in Verification of Boyle's Law of Ideal Gases.
Specifications- Category
- Physics Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
Tick items as you collect them. Tap + to see the product, specifications and buy options.
Stay safe
- The air enclosed in the tube must be completely dry (moisture causes vapor pressure deviations).
- Wait at least 2 minutes after adjusting mercury levels so gas temperature returns to room temperature.
- Never touch the enclosed gas bulb/tube with bare hands during readings to avoid heating.
- Take readings at the top of the mercury meniscus with eyes at the same horizontal level.
Steps
- 1Record the ambient room temperature and atmospheric pressure (H) using the Fortin's barometer in cm of Hg.Observation
Record laboratory barometric atmospheric pressure H = 75.8 cm Hg from Fortin barometer.
SafetyCheck mercury reservoir and rubber tubing for leak-tight connections.
- 2Check that the apparatus is set vertical with a plumb line.Observation
Align mercury levels in both closed and open limbs to read equal baseline zero difference.
SafetyWear nitrile safety gloves when working with mercury-filled glass apparatus.
- 3Adjust the open mercury tube to bring the mercury levels in both limbs to the same height (gauge pressure = 0).Observation
Raise open limb slowly by 10 cm; enclosed air column in closed limb compresses visibly.
SafetyRaise limb slowly to avoid mercury surging or column separation.
- 4Note the initial length of the enclosed dry air column (l1), which is proportional to volume V1.Observation
Wait 2 minutes for thermal equilibrium; record mercury difference h and closed tube air column length V.
SafetyKeep room temperature stable without direct sunlight on apparatus.
- 5Raise the open tube by 5 cm to increase the pressure. Record the difference in mercury levels (h) and new air column length (l).Observation
Lower open limb below closed limb to test rarefaction state (P < H).
SafetyDo not drop limb slider; clamp securely after every displacement.
- 6Calculate total pressure P = H + h and compute product P × l.Observation
P · V products calculate to 1500, 1498, 1501, 1496, 1500 cm² Hg, verifying Boyle's Law.
SafetyKeep mercury spill collection tray under apparatus at all times.
- 7Lower the open tube below the closed tube by several steps to take negative gauge pressure readings (P = H - h) and verify P × V = constant.
Tap + on a step to see what you will observe and any safety tips.
Record your observations
| Atmospheric H (cm Hg) | Manometer Difference h (cm Hg) | Total Pressure P = H ± h (cm Hg) | Air Column Length V (cm) | P · V Product (cm² Hg) |
|---|---|---|---|---|
| 75.8 cm Hg | -15.8 cm Hg | 60.0 cm Hg | 25.0 cm | 1500.0 |
| 75.8 cm Hg | -5.8 cm Hg | 70.0 cm Hg | 21.4 cm | 1498.0 |
| 75.8 cm Hg | +0.0 cm Hg | 75.8 cm Hg (Atm) | 19.8 cm | 1500.8 |
| 75.8 cm Hg | +9.2 cm Hg | 85.0 cm Hg | 17.6 cm | 1496.0 |
| 75.8 cm Hg | +24.2 cm Hg | 100.0 cm Hg | 15.0 cm | 1500.0 |
Tap a highlighted cell to write your own observation.
Result and conclusion
The product of total absolute pressure P and air column volume V remains constant within 1.2% variance. The P versus 1/V graph is a straight line through the origin.
| Observation | What it means |
|---|---|
| Inverse Proportionality | Pressure P and volume V exhibit strict inverse proportionality (P ∝ 1/V) at constant temperature. |
| Constant Product P·V | Product P · V remains constant at 1499 ± 3 cm² Hg across all five hydrostatic compression trials. |
| Linear P vs 1/V Graph | A plot of absolute pressure P against reciprocal volume (1/V) yields a straight line passing through origin. |
| Isothermal Assumption Valid | Allowing 2 minutes equilibrium between height adjustments prevents adiabatic temperature fluctuations. |
Sample readings. Replace with your own results.