Stats Tutorial - Instrumental Analysis and Calibration

Uncertainties for Volumetric Glassware

Volumetric glassware, such as pipettes, burettes, and flasks, is required when performing any analytical determinations. This page provides a table of typical uncertainty values for the calibrated volume of such glassware. Since these are based on the mean and standard deviation of the volumes delivered for a batch of glassware, they are treated as random errors.

Note that actual errors in volume can be much larger than suggested by these uncertainties if the glassware is dirty, or used incorrectly. This could be considered as a source of gross error in the resulting values.

Item	Volume (mL)	Uncertainty (mL)
Burette	50.00	±0.02
Transfer pipette “To Deliver”	50.00	±0.05
	30.00	±0.04
	25.00	±0.03
	20.00	±0.02
	15.00	±0.03
	10.00	±0.02
	5.00	±0.01
	2.000	±0.006
	1.000	±0.006
Mohr (graduated) pipette	10.00	±0.05
Volumetric flask	1000.0	±0.30
	500.0	±0.15
	250.0	±0.12
	100.00	±0.08
	50.00	±0.05
	25.00	±0.03
	10.00	±0.02

Propogating Volumetric Uncertainties:

Since the uncertainty in the volume of an item of volumetric glassware is treated as though it is random, the uncertainty in the final concentration obtained using such glassware is propated accordingly. As an example, consider the use of a transfer pipette and volumetric flask to dilute a solution which has an initial concentration of 1.000±0.001 M. The new concentration, C_f is:

C_f = C_i × V_pipette ÷ V_flask

The uncertainty in the new concentration is therefore:

where ΔX signifies the uncertainty in the value of X.