Units and measures used in Homeopathic system:

- Sumit Goel.

METROLOGY

Metrology is the science of weights and measures. It encompasses a study of the various systems of weights and measures, their relationships and knowledge of the mathematics involved. Weights and Measures are an accumulation of facts concerning the various systems, with tables of conversion factors and practical equivalents.

METRIC SYSTEM

METRIC MEASURES OF MASS - WEIGHT

1 ton = 1000 kg

1 quintal = 100 kg

1 kilogram = 1000 g

1 hectogram = 100 g

1 dekagram = 10 g

1 decigram = 1/10 g = 0.1 g

1 centigram = 1/100 g = 0.01 g

1 milligram = 1/1000 g = 0.001 g

1 microgram = 1/1000 mg = 0.000001 g

1 nanogram = 1/1000 mcg= 0.001 mcg

1 picogram = 1/1000 ng = 0.001 ng

METRIC MEASURES OF CAPACITY - VOLUME

1 kiloliter = 1000 l

1 hectoliter = 100 l

1 dekaliter = 10 l

1 deciliter = 1/10 l = 0.1 l

1 centiliter = 1/100 l = 0.01 l

1 milliliter = 1/1000 l = 0.001 l

1 microliter = 1/1000 ml = 0.000001 l

1 litre = 1000.028 cc

METRIC LINEAR MEASURES - LENGTH

1 kilometer = 1000 m

1 hectometer = 100 m

1 dekameter = 10 m

1 decimeter = 1/10 m = 0.1 m

1 centimeter = 1/100 m = 0.01 m

1 millimeter = 1/1000 m = 0.001 m

1 micron = 1/1000 mm = 0.000001 m

1 nanometer = 1/1000 micron = 0.000000001 m

RELATION OF CAPACITY TO WEIGHT

1 liter = 1000 milliliters = 1000.028 cubic centimeters = 997.18 grams (at 20oC) ? 1 kilogram

THE IMPERIAL SYSTEMS

AVOIRDUPOIS WEIGHT

Imperial system of weights and measures is commonly known as Avoirdupois system and was formerly recognized by the British Pharmacopoeia. 'Avoirdupois' is derived from the French words 'avoir' and 'pois' meaning 'to have weight'. The Imperial Standard Pound is cylindrical, being about 1.15 inches in diameter and about 1.35 inches thick, with an encircling groove or channel about 1 inch from its under surface, into which fits the ivory fork used to lift the cylinder. The latter is made of platinum and bears the inscription: P.S. 1884, 1 lb. This cylinder was adopted as the Imperial Standard Pound by the Weights and Measures Act, 1878, 1 lb. being defined in the act as the weight of the cylinder in vacuo.

All other measures of mass are derived from the Imperial Standard Pound, thus -

* 1/16th part of Imperial Standard lb. is 1 oz avoir Or 1 lb. = 16 oz avoir.

* 1/7000th part of Imperial Standard lb. is 1 gr. Or 1 lb. = 7000 gr.

It follows from this that 1 oz avoirdupois contains 7000/16 = 437.5 grains.

AVOIRDUPOIS WEIGHT

1 ounce = 437.5 grains

1 pound = 16 ounces = 7000 grains

1 stone = 14 pounds

1 hundredweight (cwt.) = 112 pounds

1 ton = 20 hundredweights = 2240 pounds

APOTHECARY OR TROY WEIGHT

The Imperial System includes a set of special weights known as APOTHECARIES OR TROY WEIGHTS. This system was used by the physicians in writing prescriptions and by the pharmacists in dispensing and retail trade.

These are based on the grain (as defined above) and are as follows -

20 grains = 1 scruple

60 grains = 1 drachm

480 grains = 1 Apothecaries or Troy ounce

12 Apothecaries or Troy ounce = 1 Apothecaries or Troy pound

The following points should be noticed -

1. The grain is the same in both Avoirdupois and Apothecaries' Systems.

2. There is no counterpart in the Avoirdupois System to the scruple of the Apothecaries' system.

3. Care must be taken not to shorten the word drachm to dram, which is 1/16 of the Avoirdupois ounce, and therefore contains 437.5/16 = 27.34375 grains, whereas the drachm contains 60 grains.

4. Care must be taken to distinguish the Apothecaries ounce and the Avoirdupois ounce.

The word 'ounce' or its abbreviation 'oz' without qualification means Avoirdupois ounce.

The Apothecary ounce is 42.5 gr heavier than the Avoirdupois ounce.

5. The Apothecaries or Troy pound is not used in Pharmacy and may be discarded. But, the Apothecary pound is 1240 gr lighter than the avoirdupois pound.

APOTHECARY WEIGHT

1 scruple = 20 grains

1 drachm = 3 scruples = 60 grains

1 ounce = 8 drachms = 24 scruples = 480 grains

1 pound = 12 ounces = 96 drachms = 288 scruples = 5760 grains

1 hundredweight = 100 pounds

1 ton = 20 hundredweights = 2000 pounds

TROY WEIGHT

1 pennyweight (Pwt)= 24 grains

1 ounce = 20 pennyweights = 480 grains

1 pound = 12 ounces = 240 pennyweights = 5760 grains

LATIN NAME ENGLISH NAME EQUIVALENT (GRAINS]

Granum Grain (avoir; apoth) 1 gr

Scrupulus Scruple (apoth) 20 gr

Drachma Drachm (apoth) 60 gr

Uncia Ounce (avoirdupois) 437.5 gr

Uncia Ounce (apoth) 480 gr

Libra Pound (avoirdupois) 7000 gr

Libra Pound (apoth) 5760 gr

MEASURES OF CAPACITY (VOLUME]

The Imperial Standard Gallon is the standard measure of capacity and is a derived standard, being the volume occupied by 10 Imperial Standard pounds weight of distilled water, weighed in air, at 62oF and with the barometer at 30 inches.

All other measures of capacity are derived from the Imperial Standard Gallon -

* 1/8 part of Imperial Standard Gallon is 1 pint

* 1/16 part of Imperial Standard Gallon is 1 fluid ounce

* 1/8 part of fluid ounce is 1 fluid drachm

* 1/60 part of fluid drachm is 1 minim

The following points should be noticed - 1. In measures of capacity, there is no counterpart to the scruple.

2. The symbols for fluid drachm and fluid ounce are identical with those used for drachm and troy ounce for solids by weight respectively.

3. For solids, there are two ounces, the avoirdupois and the troy, but for liquids, there is only one fluid ounce.

4. The apothecary pint contains 16 fluid ounces, whereas the imperial pint contains 20 fluid ounces.

LATIN NAME ENGLISH NAME EQUIVALENT

Minimum minim

Gutta Drop

Fluidrachma fl. drachm 60 minims

Fluiduncia fl. ounce 8 fl. drachms

Octarius Pint 20 fl. ounces

Congius Gallon 8 pints

IMPERIAL MEASURE (BRITISH]

1 fl. drachm = 60

1 fl. ounce = 8 fl. drachms = 480

1 pint = 20 fl. ounces = 160 fl. drachms = 9600 (

1 quart (qt.) = 2 pints

1 gallon = 8 pints = 160 fl. ounces = 1280 fluid drachms = 76800 (

APOTHECARY OR WINE MEASURE (US]

1 fl. drachm = 60 (

1 fl. ounce = 8 fl. drachms = 480 (

1 pint = 16 fl. ounces = 128 fl. drachms = 7680 (

1 quart (qt.) = 2 pints

1 gallon = 8 pints = 128 fl. ounces = 1024 fl. drachms = 61440 (

1 barrel = 31 gallons

RELATION OF CAPACITY TO WEIGHT

1 gallon = The volume of 8.337 avoir lb of distilled water at 62oF

1 fluid ounce = The volume of 437.5 grains of distilled water at 62oF (Imperial Standard]

= The volume of 454.6 grains of distilled water at 77oF (Apothecary]

1 minim = 0.91 troy grain (Imperial]

= 0.949 grain (Apothecary]

1 fl. dr. = 54.68 grains (Imperial]

= 56.96 grains (Apothecary]

1 fl. oz. = 437.5 grains (Imperial]

= 465.69 grains (Apothecary]

1 pt. = 8750 grains (Imperial]

= 7261.11 grains (Apothecary]

RELATIONSHIP OF WEIGHTS AND MEASURES

LINEAR MEASURE

1 meter = 39.4 inch (39.37 in.) = 3.280833 feet = 1.093611 yards

1 centimeter = 0.39370 inch

1 inch = 2.54 cm = 25 mm (25.4 mm)

1 foot = 304.8 mm = 30.48 cm = 0.3048 m

1 yard = 914.4 mm = 91.44 cm = 0.9144 m

1 mile = 1.6 km (1.6093 km)

1 km = 0.6214 mile

1 cubic inch = 16 cc (16.3872 cc)

1 sq. meter = 1.196 sq. yards

LIQUID MEASURE

1 ml = 16.2 minim (16.23 minim)

1 fluid drachm = 4 ml (3.697 ml)

1 fluid ounce = 30 ml (29.57 ml)

1 pint = 473 ml

1 gallon = 3785 ml (3.7853 liters) (US standard] = 4543 ml (4.5436 liters) (Imperial standard] WEIGHT

1 kg = 2.2046 lb

1 pound avoir = 454 g (453.59 g)

1 ounce avoir = 28.4 g (28.35 g)

1 ounce apoth = 31.1 g

1 gram = 15.4 gr (15.432 gr)

1 grain = 65 mg

DOMESTIC / HOUSEHOLD MEASURES (APPROXIMATE]

DOMESTIC MEASURES ENGLISH EQUIVALENTS METRIC EQUIVALENTS

1 drop * 1 minim 0.06 ml.

1/2 teaspoonful 1/2 fluid drachm 2 ml.

1 teaspoonful 1 fluid drachm 5 ml.

1 dessert-spoonful 2 fluid drachm 8 ml.

1 tablespoonful 4 fluid drachm 15 ml.

2 tablespoonful 8 fluid drachm 30 ml.

1 wine glass 2 fluid ounces 60 ml.

1 teacupful 4 fluid ounces 120 ml.

1 tumblerful (small) 8 fluid ounces 240 ml.

1 tumblerful (large) 10 fluid ounces 300 ml.

* It should be emphasized that 1 drop is not equivalent to 1minim and that 60 drops are not equivalent to 1 fluid drachm. This impression arises from the fact that 60 ordinary drops of water are about equal to 1 fluid drachm, but the volume of a drop of fluid depends on many factors, including density, temperature, viscosity, surface tension and the size and nature of the orifice from which it is dropped.