A chemical titration is a precise technique in chemistry used to determine the exact concentration of a chemical, in this case an acid.
First up, an accurately weighed amount of sodium carbonate powder is mixed with distilled water and made up to exactly 500ml. It has to be perfect, one too many drops and it is time to start again.
An accurate 20ml of this solution is placed in a conical flask. The hydrochloric acid with a coloured indicator solution is placed into the long thin tube and run slowly through a tap. At the exact volume the indicator changes colour, the reaction is complete and the tap is closed.
Using chemical calculations, the exact concentration of the hydrochloric acid can be calculated. It takes a steady hand to do this well!