After a drop of the reagent (a mixture
of iodide and starch) from another syringe falls down and moves
along the path, it stops and merges with the sample drop. By this,
the total volume would become 50mL. The whole drop still
hangs on the glass auxiliary electrode. When, another drop (water
from the third syringe) comes to merge, the gravitational force of
the whole liquid drop becomes high enough to make the drop
detach and moves out from the glass auxiliary electrode