Volumetric flask is a transparent conical shaped glass lab ware.
It is specifically used to hold liquids materials.
The flask can be made of glass or plastic.
But the ones made of glass are preferred as they can hold harsh chemicals.
It is calibrated in such a way that it has fixed volume at the mark provided near the neck.
It finds its use mainly in chemical and biochemical labs .
Volumetric flask parts:
Volumetric flask has two pieces as seen in the picture.
- The flask
- Lid to close the flask mouth.
The flask is large enough to accommodate the desired volume of the liquid. Also there is a small amount of space above the mark to provide for mixing of the liquid.
The lid is a small solid piece of glass having a plug or cork like shape to fit into the mouth of flask and also holder to hold it.
The lid fits exactly into the mouth of the flask without any chances of leak in case the filled flask is vigorously shaken.
Procedure for operation of the flask:
As mentioned before, it is widely used for purposed like making a mixture of liquids.
When small solution of solid or liquid has to be made,
a) A weighed quantity of solid or measured volume of liquid are first take into flask by pipette.
b) The solvent liquid is added to the flask to level well below the mark.
c) The lid is closed and the flask is tilted and shaken vigorously. This tilting creates space in the round portion of the flask and helps in effective mixing. Care should be taken to see that no liquid leads out of the lid.
d) Once the solute is completely mixed, the lid is opened, flask is place over a flat table. The solvent liquid is then carefully added to reach up to the mark.
e) The mark is considered reached when liquid meniscus touches exactly the mark. The meniscus would be a concave one for aqueous solutions.
Thus fixed volumes of acids, bases and buffers are made using the round bottom flask.
Volumetric flask sizes
The flask are available in various sizes like 1 liter, 500ml, 250ml, 100ml, 50ml, 25ml and also 10ml.
Even more sizes could be available with vendors. Check with them if you need in your labs.
Applications of round bottom flask:
- To make up to the desired volume of mixtures.
- To prepare exact quantity of acids, bases or buffers at desired pH.
- For storage of prepared chemicals for future use.