The Pharmacopeial medicine dropper consists of a tube made of glass or other suitable transparent material that generally is fitted with a collapsible bulb and,while varying in capacity,is constricted at the delivery end to a round opening having an external diameter of about 3mm.The dropper,when held vertically,delivers water in drops each of which weighs between 45mg and 55mg.

In using a medicine dropper,one should keep in mind that few medicinal liquids have the same surface and flow characteristics as water,and therefore the size of drops varies materially from one preparation to another.

Where accuracy of dosage is important,a dropper that has been calibrated especially for the preparation with which it is supplied should be employed.The volume error incurred in measuring any liquid by means of a calibrated dropper should not exceed 15%,under normal use conditions.