Recommended table for the density of water between 0 °C and 40 °C based on recent experimental reports

A volume calibration that involves reading a meniscus will have a higher standard deviation than a mass calibration using the same balance.

“A volume calibration that involves reading a meniscus will have a higher standard deviation than a mass calibration using the same balance.”

ASTM E542 suggests correction for evaporation becomes important for volumes below 0.1 cm3.

“ASTM E542 suggests correction for evaporation becomes important for volumes below 0.1 cm 3 [18]; however, this standard does not provide the necessary methods and corrections.”

Evaporation is a more important consideration for smaller volumes, which have a larger surface area to volume ratio, and may be negligible for many volumes.

“Evaporation is a more important consideration for smaller volumes (with a larger surface area to volume ratio) and may be negligible for many volumes.”

The uncertainty of a balance is typically larger than its resolution.

“The uncertainty of a balance is typically larger than its resolution (see example values in Table 2 of Reference [18]).”

Measurement uncertainty combines several contributing factors; for calibrating glassware these include the accepted standard deviation of the calibration process, operator effects, water temperature measurement, water density, thermal expansion of the glassware, standard masses or calibrated balance, density of standard masses, air density, drain time effects, and evaporation, listed in descending

“Measurement uncertainty combines the result of several contributing factors, which includes the following for calibrating glassware, listed in descending order of their usual importance [18]:”

The standard deviation used in the uncertainty analysis must be specific to the process.

“The standard deviation used in the uncertainty analysis must be specific to the process.”

The International Organization of Legal Metrology (OIML) is another organization with relevant published standards.

“The International Organization of Legal Metrology (OIML) 18 is another organization with relevant published standards.”

The example uncertainty budgets in References [18] and [17] are in accordance with accepted methods.

“These examples are in accordance with the accepted methods.”

Individual staff members can be very repeatable reading a meniscus, but there may be systematic differences between staff members.

“Individual staff members can be very repeatable reading a meniscus, but there may be systematic differences between staff members.”

In function, SOP 14 and ASTM E542 are equivalent; however, the NIST documentation tends to have more detailed procedural steps and practical advice.

“In function, they are equivalent; however, the NIST documentation tends to have more detailed procedural steps and practical advice.”

SOP 14 in NISTIR 7383 and ASTM E542 are accepted and validated practices or procedures for the gravimetric calibration of laboratory glassware.

“Standard Operating Procedure (SOP) 14 in NISTIR 7383 [17] and ASTM E542 [18] are accepted and validated practices or procedures and are recommended for the gravimetric calibration of laboratory glassware.”

References [18] and [17] give example uncertainty budgets for calibrating glassware.

“There is no need to start an uncertainty budget from scratch, as References [18] and [17] give example uncertainty budgets for calibrating glassware.”

ASTM E542-22 Table 6 suggests a range for the thermal coefficient of cubical expansion uncertainty of 5% to 10% of the value.

“ASTM E542-22 Table 6 [18] suggests a range for the thermal coefficient of cubical expansion (CCE) uncertainty of 5 % to 10 % of the value.”

ASTM E542 contains many best practices for use of volumetric glassware, for example, pipetting onto wetted walls; using specified and consistent wait times when emptying; avoiding liquid splashes above the graduation line; and using a burette stopcock fully open until close to the target volume, then slowing the flow.

“ASTM E542 contains many best practices for use of volumetric glassware, for example, pipetting onto wetted walls; using specified and consistent wait times when emptying; avoiding liquid splashes above the graduation line; using a burette stopcock fully open until close to the target volume target, then slowing the flow; etc.”

The appendix of ASTM E542 includes example values from water and air density calculations that could be used for software quality assurance, as does GLP 10 (water density only).

“The appendix of ASTM E542 [18] includes example values from the water and air density calculations that could be used for this purpose, as does GLP 10 [17] (water density only).”

The currently accepted expressions to calculate the density of air-saturated water are originally sourced from Tanaka et al. [19] and are duplicated in both ASTM E542 [18] and SOP 14 [17].

“The currently accepted expressions to calculate the density of air-saturated water are originally sourced from Tanaka et al. [19] and are duplicated in both ASTM E542 [18] and SOP 14 [17].”

ASTM E542 requires water that meets ASTM D1193 Type III or ISO 3696 Class 3 specifications (or better).

“ASTM E542 [18] requires water that meets ASTM D1193 Type III or ISO 3696 Class 3 specifications (or better).”

Both GMP 3 and ASTM E542 have two options for reading the meniscus.

“Both GMP 3 and ASTM E542 have two options for reading the meniscus.”

ASTM E542 requires water thermometer resolution of 0.01°C and uncertainty (k=2) of 0.1°C.

“SOP 14 states the requirements for the water thermometer as “resolution and uncertainty less than 0.1 °C”, and ASTM E542 requires resolution of 0.01°C and uncertainty (k=2) of 0.1 °C.”

ASTM E542 Section 17.7 notes that when using a calibrated balance under conditions that differ significantly from the reference conditions for conventional mass, additional uncertainty evaluation should be considered.

“ASTM E542 Section 17.7 notes that when using a calibrated balance under conditions that differ “significantly” from the reference conditions for conventional mass (i.e., 20 °C, 8 g⁄cm 3 reference density, 0.0012 g⁄cm 3 reference air), additional uncertainty evaluation should be considered [18].”

In ASTM E542 Section 17.7, "significantly" is not quantified.

““Significantly” is not quantified, so to avoid the additional evaluation, if there is a question as to whether the conditions are sufficiently close to conventional mass reference conditions, mass standards should be used as the reference rather than a calibrated balance.”

The calibration procedures for volumetric glassware (SOP 14 and ASTM E542) are applicable to volumetric containers made from other materials such as metal or plastic, provided the material of construction is stable and a value for the cubical coefficient of thermal expansion is available.

“The calibration procedures for volumetric glassware (SOP 14 [17] and ASTM E542 [18]) are applicable to volumetric containers made from other materials such as metal or plastic, provided the material of construction is stable and a value for the cubical coefficient of thermal expansion is available.”