VOLUMETRIC FLASK

 APPEARANCE

It is made of glass or plastic and consists of a flat bottomed bulb with a long neck, 

usually fitted with a stopper. 

The stopper is normally made in a chemically resistant plastic such as polypropylene rather than glass. 

The neck has a single ring graduation mark and a label. 

The label should show the nominal volume, tolerance, calibration temperature, class, 

relevant manufacturing standard and the manufacturer’s logo. 

The glass or plastic is generally colourless 

but may be amber colored for handling light sensitive compounds 

such as silver nitrate or vitamin A.

HOW TO USE IT

Volumetric flasks are used for making up solutions to a known volume.

Example

Make 1M solution of sodium chloride.

1. Pour distilled water until quarter of 1000 mL volumetric flask.

2. Weigh out 58.4 g (1Mol) of sodium chloride.

3. Put sodium chloride into volumetric flask.

4. Swirl the flask gently until all the solid is dissolved.

    You may want to top up distilled water while dissolved the sodium chloride.

5. Then add more distilled water until the bottom of the meniscus touches the 

    graduation line.

NOTE

The meniscus can be made clearer by holding a black card behind the neck just below the line of sight.

The stopper is then placed in the neck and the whole flask inverted repeatedly to homogenize the solution.

Care must be taken when making up concentrated solutions because 500 ml of a concentrated solution added to 500 ml of distilled water does not necessarily make 1000 ml and thus the volume may change when the solution is homogenized.

A well known example of this is found when mixing water ethanol mixtures. 

In this case it is better to make up near the mark,

then homogenize, 

then make up to the mark. 

Volumetric flasks have also been used as decanters, for brandy, malt whisky, or other alcoholic beverages. 

They are less decorative than the fancy crystal decanters made by Baccarat and similar vendors, 

but they have stoppers that seal well enough to prevent evaporative losses.

REFERENCES

1. ^ Oxford English Dictionary 1989 edition
2. ^ ^{a b c} British Standard 6523 (1984) Glass beakers for laboratory use
3. ^ A. I. Vogel (1974) Practical Organic Chemistry Third edition (Longman, London) page 46 ISBN 0-582-44245-1