Editing Drop (unit) (section)

==History==

In the first decade of the 19th century, the [[Minim (unit)|minim]], the smallest unit of [[Apothecaries' system|Apothecary Measure]], was promoted by the pharmaceutical and medical establishments as an alternative to the drop.<ref name="Nicholson1809">{{cite book|last=Nicholson|first=William|author-link=William Nicholson (chemist)|title=The British encyclopedia, or Dictionary of arts and sciences comprising an accurate and popular view of the present improved state of human knowledge|url=https://books.google.com/books?id=jYAPAAAAQAAJ&pg=PT264|access-date=18 December 2011|year=1809|publisher=Whittingham|page=264}}</ref> It was noted that the size of a drop can vary considerably depending on the viscosity and specific gravity of the fluid, as well as the size and shape of the vessel from which it is poured. (At the time, [[surface tension]] was not well understood.) The minim came with a set of procedures for ensuring accurate measurement, specifically, diluting powerful medicines that had previously been measured by the drop, then using a "minimometer" or "minim glass" (graduated pipette) with minim marks at regular intervals. The minim was defined as one 60th of a [[fluid dram]] or one 480th of a [[fluid ounce]].<ref>{{cite book|author1=Royal College of Physicians of London|author2=Richard Powell|title=The pharmacopoeia of the Royal College of Physicians of London, M. DCCC. IX|url=https://books.google.com/books?id=pCPrAAAAMAAJ&pg=PA6|access-date=18 December 2011|year=1809|publisher=Longman, Hurst, Rees, and Orme|pages=6–7}}</ref> This is equal to about 61.6 μL (U.S.) or 59.2 μL (Britain).

Pharmacists have since moved to metric measurements, with a drop being rounded to exactly 0.05 mL (50 μL, that is, 20 drops per milliliter). In hospitals, intravenous tubing is used to deliver medication in drops of various sizes ranging from 10 drops/mL to 60 drops/mL. A drop is abbreviated ''gtt'', with ''gtts'' used for the plural, often seen on [[prescription (medical)|prescription]]s.<ref name=m10624415/> Other sources abbreviate ''gt'' for singular, and ''gtt'' for plural.<ref>{{cite web|url=http://www.dictionary.com/browse/gutta|title=Gutta - Define Gutta at Dictionary.com}}</ref><ref>{{cite web|url=http://medical-dictionary.thefreedictionary.com/gutta|title=gutta|via=The Free Dictionary}}</ref> These abbreviations come from ''gutta'' (plural ''guttae''), the Latin word for drop.<ref>{{cite book|author=Hugh Cornelius Muldoon|title=Lessons in pharmaceutical Latin and prescription writing and interpretation|url=https://archive.org/details/lessonsinpharma00muldgoog|access-date=8 March 2012|year=1916|publisher=John Wiley & sons, inc.|page=[https://archive.org/details/lessonsinpharma00muldgoog/page/n160 147]}}</ref><ref name=m10624415>{{cite journal |author=McGarry RC, McGarry P |title=Please pass the strychnine: the art of Victorian pharmacy |journal=Canadian Medical Association Journal |volume=161 |issue=12 |pages=1556–8 |year=1999 |pmid=10624415 |pmc=1230877}}</ref>