GLP 13 – 2019 Page 1 of 2

This publication is available free of charge from: https://doi.org/10.6028/NIST.IR.7383 -2019

GLP 13

Good Laboratory Practice

for

Drying “To Contain” Volume Standards

1 Purpose for drying

Vessels calibrated "To Contain"(TC) must be dried of all measurable water to obtain an 

"empty" weight. The drying process should not contaminate the container; otherwise, it 

will need to be re-cleaned before further calibration or volumetric use. The following is 

presented as guidance when drying is required. 

2 Methods for drying

Drain as much of the residual water as practical before starting any drying process. If time 

is not a consideration, a glass tube may be inserted into the container to blow clean dry air 

(or nitrogen) through it to evaporate the residual water film. A filter or dust trap may be 

necessary to pre-clean the air used. Air lines must be selected to ensure that aging and wear 

do not introduce contaminants. Air may be drawn through a tube connected to a vacuum 

pump, but with some danger of drawing in dirty air from the surroundings. Clean absorbent 

cotton placed at the neck opening can minimize the entrance of foreign matter. Compressed 

air systems may introduce finely atomized oils or moisture into the air which may not be 

visible. If laboratory quality air is not available, nitrogen may be used. 

Cleaning with solvents may be performed; ethanol is the preferred medium. Preliminary 

rinsing with acetone will remove large amounts of water, with which it is infinitely 

miscible, but this solvent often contains impurities such as traces of oils that could deposit 

on the container walls and be a disposal problem. Thus, a final alcohol (preferably ethanol

or methanol) rinse is recommended, even if acetone is used to remove most of the water. 

Care must be taken to ensure that the alcohol is not mixed with acetone, and that the alcohol 

is not denatured with oils to an extent that will leave residue on the standard. The alcohol 

is drained as much as possible, followed by air drying as described above. 

Some metal containers may be internally coated to minimize corrosion. When present, it 

should be ascertained that such coatings are not affected by alcohol or acetone; otherwise, 

solvent treatments should not be used. 

The external surfaces of all containers should be clean when gravimetric calibrations are 

performed. Otherwise, any removal of external dust or dirt during the measurement process 

could cause errors of unknown magnitude. 

Analytical glassware should not be dried by heating in an oven as the glass may suffer nonelastic expansion and put the glassware out of calibration.

Calibration Tip

Cover a vessel after it is clean and dry to minimize contaminants from collecting 

inside the vessel. Clean and dry the flask one to two days prior to the calibration 
GLP 13 – 2019 Page 2 of 2

This publication is available free of charge from: https://doi.org/10.6028/NIST.IR.7383 -2019

and allow the flask to come to equilibrium with the environment. Obtain an initial 

baseline “dry weight” of the clean container for use as a dry reference weight on 

subsequent weighing and drying cycles.

Safety Note

Safety Data Sheets (SDSs) must be available in the laboratory and should be 

reviewed to ensure safe handling and disposal of all chemicals noted in this 

procedure. Care must be taken to avoid mixing chemicals such as acetone and 

alcohols in the laboratory.