Automatic burettes are used for series of tests. It is connected with a bottle, which contains the titration solution. The air is pumped into the bottle by a small rubber air pump, created the pressure in the bottle which the rises the solution to the top of burette. When the burette is full, the valve is released; the pressure in the bottle falls and the burette automatically sets itself to zero. Work with automatic burettes is by far faster and the consumption of standard solution is smaller. Automatic titrators are known as differential titrators. These instruments add titrant at a constant rate and electronically take the derivative of the potential versus time curve that is produced.