Metrology

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Metrology

Metrology:

It is the science of weights and measures.

Definition

Types of systems

Old apothecaries system.

Classical Metric system.

Old apothecaries system:

This system is used by older prescribers, it is basic unit is grain.
Types of systems :

equivalent

abbreviation
Name
-----
gr
Grain
60 grains
dr
Drachm
8 dr
oz
ounce
12 oz
Ib
pound
Grain : is defined as the weight of a grain of wheat and it is equivalent to 0.06 gm (60 mg).
A . Units of weights:


Equivalent
Abbreviation
Name
---------
---------
Minims
60 minims
Fl.dr
Fluid drachm
8 fl.dr
Fl.oz
Fluid ounce
16.fl.oz
o
pint
Minim(m): is defined as the volume corresponding to 0.06 ml (1 drop).
b. Units for measuring
VOLUME

It is very simple because it is standarized system & the difference between one unit &other is tenth, therefore it named Decimal system.
Metric system
(international system)
1/1000000
1/1000
1/100
1/10
unit
10
100
1000
One
million
One thousand
One hundered
One tenth


tenth
handered
thousand
Micro
µ
Milli
o.oo1
Centi
0.01
Deci
0.1
Gram(gm)
Liter(l)
Meter(m)
Deca
Hecta
kilo

Liter: it is the volume of 1 kg of water at 4 degree centegrate.

Gram: it is the weight of one (ml)


Conversion from apothecaries system to metric system:
A. units of weights
G 0.06 gm
Dr. 4 gms
0z 30 gms
B. Units of liquid
m 0.06 ml
Fl.dr 4 ml
Fl.oz 30 ml
0 500 ml

A. units for weight

gm 15 gr
kg 2.2 Ib

B. Units for volume of liquids

ml 15 M
L 2 0

Conversion from metric system to apothecaries system

1 minim₌ 0.06 ml
Drop
1 ml
20 drop
2.5 ml
Tea spoonful (small)
5 ml
Tea spoonful (large)
15 ml
Table spoonful
30 ml
Coffee cupful
150 ml
Tea cupful
250 ml
glassful
Household measures
(domestic measures)

If a cough syrup contains 0.3 g of drug in 100 ml, howmany milligram are contained in each TABLE spoonful dose???
Conversion to apothecaries system???


0.3 100 ml
X 15