Gay-Lussac Calibrated Pycnometer (25.000 cm³)
Precision borosilicate glassware featuring ground glass capillary stopper designed to maintain an invariant volumetric capacity of 25.000 ± 0.003 cm³ under controlled thermal equilibrium.
Chemistry / Partial Molar Volume of Binary Mixtures
FREE TO EXPLORELABORATORY 18 · NATURAL SCIENCES
Determination of Apparent and Partial Molar Volumes in Binary Ethanol-Water Mixtures via Precision Pycnometry
To determine the density of a series of binary ethanol-water mixtures using high-precision Gay-Lussac pycnometry at 25.0 °C, compute the apparent molar volume (\phi_V) of ethanol as a function of molality, and evaluate the limiting partial molar volume of ethanol at infinite dilution (\bar{V}_2^\infty) and excess thermodynamic properties via linearized extrapolation. Explore interactive analytical gravimetry, Class A volumetric glassware and density determination.
MEASURE · CALIBRATE · ANALYSE
Your virtual chemistry laboratory.
FILLED PYCNOMETER TOTAL MASS M_FILLED—
MEASUREMENT STATUS
Ready to dispense 1.5 mol/kg of liquid.
Adjust ethanol molality V, then weigh the dispensed aliquot.
Mass observations are determined by the high-precision thermodynamic equation of state for pure liquid water. Readings reflect thermal equilibrium and analytical balance force restoration.
Physical chemistry assumptions and metrological limits
Gay-Lussac pycnometry assumes that ambient room temperature does not diverge significantly from the bath setpoint (25.00 °C) during the brief weighing period, minimizing capillary expansion overflow. At higher ethanol concentrations (> 3 mol/kg or > 15 wt%), non-linear higher-order solute-solute clustering effects require quadratic terms in the molality expansion. The physical simulation calculates binary solution densities and apparent molar volumes at 25.00 °C governed by φ_V = (1/m) · [ (1000 + m·M₂)/ρ − 1000/ρ₀ ], where solvent is Millipore water (M₁ = 18.015 g/mol, ρ₀ = 0.997047 g/cm³) and solute is anhydrous ethanol (M₂ = 46.069 g/mol, pure molar volume V₂* = 58.68 cm³/mol). In the dilute regime (m = 0.50 to 3.00 mol/kg), non-electrolyte hydrophobic hydration dictates linear apparent volume expansion: φ_V(m) = φ_V° + b_V·m, with limiting partial molar volume at infinite dilution φ_V° = V̄₂^∞ = 54.20 cm³/mol and slope b_V = +0.250 cm³·kg·mol⁻². For a calibrated 25.000 cm³ Gay-Lussac pycnometer with dry tare mass m₀ = 18.4250 g, filled pycnometer masses span 43.2529 g (m = 0.50 mol/kg, ρ = 0.99312 g/cm³) down to 42.7912 g (m = 3.00 mol/kg, ρ = 0.97465 g/cm³). Ordinary least-squares linear regression extracts the intercept b = 54.20 cm³/mol with R² = 0.99998, validating limiting partial molar volume without bias and demonstrating volumetric contraction of 4.48 cm³/mol due to interstitial cavity accommodation.
Analytical chemistry apparatus & tools.
Analytical Balance (Mettler Toledo XPE205)
Dual-range electronic analytical balance with 0.0001 g resolution, automated internal calibration, and draft-shielded pan for gravimetric measurement of pycnometer tare and filled masses.
Thermostatic Circulating Water Bath
Constant-temperature bath regulated to 25.00 ± 0.01 °C with continuous fluid circulation to equilibrate pycnometers and eliminate thermal expansion density drift.
Gravimetric Solution Prep Flasks & Syringes
Set of 100 mL airtight borosilicate volumetric and glass flasks with PTFE stopcocks used to synthesize precise binary ethanol-water solutions across 0.5 to 3.0 mol/kg.
Capillary Meniscus Wiper & Lint-Free Lens Paper
Specialized lintless optical paper used to wipe external pycnometer surfaces and blot meniscus overflow at the capillary tip without wicking interior liquid.
Reagents: Absolute Ethanol (≥ 99.8%) & Degassed Millipore Water
High-purity anhydrous ethanol (M₂ = 46.069 g/mol) and vacuum-degassed Type 1 deionized water (M₁ = 18.015 g/mol, ρ₀ = 0.997047 g/cm³ at 25.0 °C).
FOLLOW THE METHOD
A reason behind every step.
To determine the density of a series of binary ethanol-water mixtures using high-precision Gay-Lussac pycnometry at 25.0 °C, compute the apparent molar volume (\phi_V) of ethanol as a function of molality, and evaluate the limiting partial molar volume of ethanol at infinite dilution (\bar{V}_2^\infty) and excess thermodynamic properties via linearized extrapolation. Suggested independent volumetric settings: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mol/kg.
01
Pycnometer Cleaning, Drying, and Tare Weighing
Thoroughly clean the 25 mL Gay-Lussac pycnometer with chromic acid substitute, rinse repeatedly with deionized water and acetone, dry with warm filtered nitrogen, and record the dry tare mass m₀ on the analytical balance to ±0.0001 g.
02
Pycnometer Volume Calibration with Pure Water
Fill pycnometer with freshly boiled, degassed deionized water, seat capillary stopper allowing excess to overflow, equilibrate in the 25.00 °C bath for 20 minutes, wipe dry, weigh (m_water), and calculate exact internal volume V_pyc = (m_water - m₀) / ρ₀.
03
Gravimetric Preparation of Ethanol-Water Standards
Prepare six binary solutions of exact ethanol molalities m = 0.50, 1.00, 1.50, 2.00, 2.50, and 3.00 mol/kg solvent by weighing degassed water into flasks followed by anhydrous ethanol, sealing promptly to prevent volatile evaporation.
04
Pycnometer Loading and Constant-Temperature Equilibration
Rinse pycnometer twice with 3 mL aliquots of the test solution, fill to the brim, insert capillary stopper firmly, and immerse in the 25.00 °C water bath for 20 minutes to reach thermal and volumetric equilibrium.
05
Meniscus Adjustment, Exterior Drying, and Analytical Weighing
Carefully remove pycnometer from bath, swiftly touch capillary apex with lint-free paper to bring meniscus flush with the ground rim without capillary draw, wipe exterior dry, and record mass m_soln on the analytical balance to ±0.0001 g.
06
Repetition, Density Computation, and Apparent Molar Volume Calculation
Repeat duplicate trials for each concentration, compute solution density ρ = (m_soln - m₀) / V_pyc, determine apparent molar volume φ_V = [M₂/ρ − 1000(ρ − ρ₀)/(m·ρ·ρ₀)], and perform linear regression to obtain limiting partial molar volume.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into quantitative chemical insight.
Points are your recorded gravimetric observations. The regression line validates the linear mass-volume proportionality and extracts density.
ORDINARY LEAST-SQUARES FIT · m = ρ·V + m₀
φ_V = φ_V° + b_V · m ==> φ_V = 54.20 + 0.25 · m
| # | Ethanol molality m (mol/kg solvent) (mol/kg) | Filled pycnometer total mass m_filled (g) | Ethanol molality m (mol/kg) | Apparent molar volume φ_V (cm³/mol) | Remove |
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