Pipettes and burettes are graduated to deliver the quantities specified.
Burettes differ mainly from pipettes in having the flow of liquid controlled from below instead of from above.
The liquid in the two burettes is next brought to the same level, either by pouring it in at a or running it out at b.
It is this difference in the readings of the two burettes which measures the quantity of nickel present.
Run out the water so as to keep the level in the two burettes the same.
If burettes are wanting, and one must be used for several samples, a Mohr's burette with glass cock is the most convenient to use.
The levels of the two liquids are then brought to the zero marks of the burettes by means of the stopcocks.