Abstract: A pipettor for threaded attachment to a liquid containing jar provides for dispensing a controllable volume of liquid with a high degree of precision upon manually operating a plunger. The liquid volume dispensed in a single plunger operation is adjusted by rotation of the plunger knob. Both a linear coarse scale and a circular fine adjustment scale are provided for accurately setting the volume to be dispensed. Positive detent stops are provided for accurate volume settings. Improved air purging and plunger locking mechanisms are also provided.