Volume calibration of a 100 ml Gay-Lussac Pycnometer

Project Description

The main purpose of this project is to compare the results of a volume calibration of a glass 100 ml Gay Lussac Pycnometer. This comparison will allow the participating laboratories to test the agreement of their results despite the different used equipment. In order to get comparable results the laboratories will use the same method (gravimetric) at a temperature of 20 ºC and the same calibration liquid (water). A protocol will be drafted and will include the method, the uncertainty components to be evaluated for the uncertainty budget and the guidelines for the reporting of the results.

The proposed project should be run in close co-operation with a parallel one aiming at the volume of 5- litre glass standard.For the final schedule the laboratories must confirm their participation. This project should not exceed one year including circulation of the pycnometer and report presentation.

Final Report 2005-03-01

The comparison has been completed and the results are available in the KCDB.

This comparison involved 14 laboratories at all, and lasted one and half year.

One of the major risks was to break the glass pycnometer, witch actually happened after 5 measurements. Replacing the pycnometer and adding a correction to the first 5 volume results resolved the problem.

Globally the results are quite satisfactory. Except for one or two participants, the laboratories volume results are quite consistent with the reference value, and with each other.
The uncertainty budgets are very similar and the major uncertainty component to the final uncertainty is, for the majority of the participants, the water density.
There is a difference in the determination of the total uncertainty in some of the countries. It is probably due to the repeatability of the measurements, problems with the ambient conditions, the use of different mass standards and the use of different formulas for the volume calculation.

Some countries reported damages in the pycnometer that could influence the volume result, but at the end of the comparison the pilot laboratory examined the pycnometer and concluded that the reported defect existed already at the beginning of the comparison. The results were confirmed with the last measurement of the volume of the pycnometer by the pilot laboratory.