Managing Director, Manufacturer of Surfactant, Emulsifier,Pesticide Technical,Pesticides formulation,Deformer, R&D Scientist, Motivational speaker, Research Scholar at Manipal university and dis. CSIR-CSMCRI bhavnagar
Calibration of Pipettes, Burettes & Volumetric Flasks 1. Pipette Calibration • Step 1: Tare (zero) a beaker on an analytical balance (accuracy ±0.1 mg). • Step 2: Fill pipette with distilled water at 20 ± 0.5 °C (standard calibration temp). • Step 3: Dispense by gravity (don’t blow out). • Step 4: Weigh delivered water (mass = m). • Step 5: Calculate volume: V = \frac{m}{\rho_{water}(T)} where ρ is water density at temperature T. • Step 6: Repeat 10 times (n = 10). • Step 7: Calculate Mean (X̄) and Standard Deviation (s). • Step 8: % Error = (Measured – Nominal). • Step 9: % CV = (s / X̄ × 100). Pass if within tolerance (ISO 8655 standard). ⸻ 2. Burette Calibration • Step 1: Fill and condition burette with distilled water. Record initial & final reading. • Step 2: Deliver exactly 10.00 mL (for example) into a pre-weighed flask. • Step 3: Calculate actual volume: V_{actual} = \frac{m}{\rho} • Step 4: Correction: C = V_{actual} - V_{indicated} • Step 5: Calculate % Relative Error to check accuracy. ⸻ 3. Volumetric Flask Calibration • Step 1: Fill flask to mark (meniscus at eye level) at 20 °C. Cap & mix. • Step 2: Weigh full flask (mfull) – empty (mempty) = water mass. • Step 3: Convert mass to volume: V = \frac{m}{\rho_{water}} • Step 4: Apply thermal expansion correction of glass (αg). • Step 5: Calculate uncertainty (uC) to know precision. ⸻ 🔑 Key Takeaways • Always calibrate at 20 °C (standard lab reference temp). • Use analytical balance for highest accuracy. • Repeat multiple times for statistical reliability. • Apply correction factors (water density, thermal expansion). • Calibration ensures traceability, reliability & compliance with ISO 8655.