WEIGHTS AND MEASURES 7 



METROLOGY— WEIGHTS AND MEASURES 



Metrology is the science of weights and measures. 



Weight is the sum of the attraction of gravity existing between 

 the earth and a body upon its surface, and in weighing we simply 

 balance a substance against another known force. 



There are several standards of weights used in the United States, 

 with which the physician, veterinarian and pharmacist must become 

 familiar. Those most used are the Troy or Apothecaries' weights 

 and the Wine or Apothecaries' measures, besides which are the Avoir- 

 dupois weights, and Metric weights and measures. 



TABLE OF AVOIEDUPOIS WEIGHTS 



43Y.5 grains (gr.) := 1 ounce (oz.) 

 16 oz. = 1 pound (lb.) = (YOOO gr.) 



100 lbs. = 1 hundredweight (cwt.) 



20 cwt. = 1 ton 



This table is never used in prescribing but is the one used almost 

 exclusively in buying and selling all solid and many liquid drugs. 

 When we purchase a " pound " we get an Avoirdupois pound, or 7000 

 grains. If we order an '' oz.," we receive an Avoirdupois ounce 

 or 437.5 grains, as oz. stands for Avoirdupois ounce only. Many 

 powerful drugs, like strychnine, morphine, etc., are usually handled 

 in Ys oz. bottles, but these do not contain % of an Apothecaries' ounce 

 or 60 grains, but Vs of an Avoirdupois ounce or about 54.7 grains. 



TABLE OF apothecaries' OK TEOY WEIGHTS 



20 grains (gr.) = 1 scruple (9) 



3 scruples = 1 drachm (3) = 60 gr. 



8 drachms = 1 ounce (S) = 480 gr. 



12 ounces = 1 pound (ft) = 5760 gr. 



The grain used in this system is the same as that of the Avoirdu- 

 pois, but the ounces contain 480 grains against 437.5 of the Avoir- 

 dupois, while the pound, ft. contains 12 ounces of 480 grains, or 

 5760 grains, instead of the Avoirdupois pound of 16 ounces of 437.5 

 each or 7000 grains. 



Of this table only the grains, drachms and ounces should be used 

 in prescription writing. The scruple was used at one time, but is 

 largely in disuse at the present time and is unnecessary. Further- 

 more the character is not easily made, and if made carelessly or 

 blurred may be mistaken for the drachm sign. 



TABLE OF apothecaries' (oE WINe) MEASUEES 



60 Minims (n) = 1 fluidrachm (f3) 



8 Fluidrachms = 1 fluidounce (fS) 480 ms. 



16 Fluidounces = 1 pint (0.) 7680 ms. 



8 pints = 1 gallon (Cong.) 61440 ms. 



