Automatic Zero Burettes

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An automatic burette consists of a thick flask with ground glass joint, where a specially designed burette is positioned. This type of burette consists of a lower concentric glass tube. The upper part of the burette contains a short lateral tube with two openings, one open and the other connected to a rubber bulb pump, through which air is pumped inside the burette flask. A capillary tube carries the solution from the flask up to the scaled burette tube, filling it from top-down. A small outward tube fitted with a needle-valve ground glass or PTFE stopcock allows the draining of the burette. The solution level inside the burette is kept a fixed point (which corresponds to the number 0 from the scale) thanks to the capillary tube end being slightly above the 0 line. Some burettes have a second stopcock, which allows you to drain the solution back inside the flask directly, without having to remove it by hand from the flask and empty it through the main tap.