Uncertainty Cause-and-Effect — NaOH Standardised Against KHP
Eurachem/CITAC cause-and-effect (Ishikawa) diagram enumerating every uncertainty source in the standardisation of a 0.1 mol/L NaOH titrant against potassium hydrogen phthalate, the first step of a GUM measurement uncertainty budget.
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title "Uncertainty sources — standardising NaOH against KHP (Eurachem CG4, A2)"
problem "c(NaOH) = 0.10214 mol/L"
category "m(KHP) — u = 0.13 mg"
cause "Weighing by difference, 2 readings"
cause "Balance linearity ±0.15 mg (rect.)"
cause "Balance calibration certificate"
cause "Dried to constant mass, 120 °C"
category "V(T) — u = 0.013 mL"
cause "Burette calibration ±0.03 mL (tri.)"
cause "Temperature ±3 °C about 20 °C"
cause "Expansion of water 2.1E-4 per °C"
cause "End point vs true equivalence"
category "P(KHP) — u = 0.00029"
cause "Certificate 100.0 ± 0.05 % (rect.)"
cause "Moisture uptake before weighing"
category "M(KHP) — u = 0.0038 g/mol"
cause "IUPAC atomic weights C H O K"
category "Repeatability — u/c = 0.05 %"
cause "5 replicate titrations"