# Weights and Measures

Objective

At the end of this lecture, student will be able to

• List the various systems of weights and measures

• Convert units within the various systems

• Compare the different systems

• Relate common household measurements to the imperial and metric measures

## Weights and measures

A thorough knowledge of weights and measures – to understand various types of calculations used in dispensing.

The two systems of weights and measures

The Imperial system

The Metric system

## The imperial system

An old system of weights and measures

The Imperial system type:

Apothecaries system

• Avoirdupois system

1. Avoirdupois weight measures

– ‘Pound’ is the standard unit for weighing

– All measures of mass are derived from the Imperial standard pound (lb)

Avoirdupois measure of weight

 Pound Ounce Grain 1 16 7000 1 437.5

2. Apothecaries weight measures

– Also known as ‘Troy’ system

– ‘Grain’ is the standard unit

Apothecaries’ measures of weight

• 20 grains = 1 scruple ()

• 3 scruples = 1 drachm/ dram (ʒ)

• 8 drachms = 1 ounce (oz )

• 12 ounces  = 1 pound (lb)

A typical set of Apothecary weight will contain the following units:

• 2 fluid ounce

• 1 fluid ounce

• 2 fluid dram

• 1 fluid dram

• ½ dram

• 2 scruple

• 1 scruple

• ½ scruple

• 5, 4, 3, 2, 1, ½ grain

 Pound Ounce Drachm Scruple Grain 1 12 96 228 5760 1 8 24 480 1 3 60 1 20

Conversion table

 I Lb 16 oz (avoir) 1 Lb 7000 grains 1oz 7000/16 = 473.5 grains 20 grains 1 scruple 60 grains 1 drachm 480 grains 1 ounce 12 ounce 1 pound 5760 grains 1 pound

Measurement of capacity in Imperial system

• The standard unit for capacity is ‘gallon’ in both apothecaries and avoirdupois system.

 Gallon Quart Pint Fluid ounce Fluid drachm Minim 1 4 8 128 1024 61440 1 2 32 256 15360 1 16 128 7680 1 8 480 1 60

Imperial measures for volume

60 minims () = 1 fluid drachm (fʒ)

8 fluid drachm = 1 fluid ounce (f)

16 fluid ounces = 1 pint (pt or O)

2 pints = 1 quart ( qt)

4 quarts = 1 gallon ( gal or C )

## The Metric System

• Most commonly used measure of weights and measures

• The three basic units of metric system – meter, gram and litre

• Other units are formed by adding prefix to one of the basic units

• Litre and gram – most commonly used basic units in pharmacy

 PREFIX VALUE Micro 1/10,00,000 Milli 1/1,000 Centi 1/100 Deci 1/10 Deca 10 Hecto 100 Kilo 1,000

Conversions – Imperial to Metric

 IMPERIAL METRIC 15.43 grains 1 gram 1 grain 65 mg 2.2 pounds 1 kg 16.23 minims 1 ml 1 minim 0.06 ml 1 fluid drachm 3.69 ml 1 fluid ounce 29.57 ml 1 pint 473 ml 1 gallon 3785 ml

Household / Domestic measures

 Domestic measures Metric system Imperial system 1 drop 0.06 ml 1 minim 1 teaspoonful 4 ml/5 ml 1 fluid drachm 1 desert spoonful 8 ml/10 ml 2 fluid drachms 1 tablespoonful 15 ml 4 fluid drachms 1 wineglassful 60 ml 2 fluid ounces 1 teacupful 120 ml (4 fluid ounce) 4 fluid ounces 1 tumblerful 240 ml (8 fluid ounce) 8 fluid ounce

Summary

• Two basic systems of weights and measures – Imperial and metric

• The two imperial systems of measures – Avoirdupois and Apothecaries

• Apothecary measure of weight – Grain, scruple, drachm ounce pound

• Avoirdupois measure of weight – Grain ounce pound

• Imperial measure of volume – minim, scruple, drachm, fluid ounce pint quart

• Common household measurements

Also, Visit:

B. Pharma Notes | B. Pharma Notes | Study material Bachelor of Pharmacy pdf

B. Pharma Handwritten Notes

B. Pharma PDF Books

B. Pharma Lab Manual

D. Pharma Lab Manual

B. Pharma 8th Semester Previous Year Question Paper

D. Pharma Notes