COLLEGE OF

PHARMACY

Dr. Mohammad Javed Ansari, PhD.

Contact info: mj.ansari@psau.edu.sa

PHARMACEUTICS-I

(PHT 224)

international systemof

weight & measurement

OBJECTIVES OF THE LECTURE

• At the end of this lecture, you will be able to explain:

• What are international system (SI) of the weights &

measurements?

• What are basic units in SI system?

• What are derived units in SI system?

• What are different conversions within metric and SI

system?

FUNDAMENTALS OF MEASUREMENTS: METRIC SYSTEM VARIANTS

•The centimetre–gram–second system of

units (abbreviated CGS or cgs) is a variant of

the metric system based on the-

• centimetre as the unit of length,

•gram as the unit of mass, and the

• second as the unit of time.

•The MKS system of units is also a variant of

metric system that expresses any given

measurement using fundamental units of

the metre, kilogram, and second (MKS).

•NOTE: FPS (Foot Pound Second) is used in

apothecary system.

FUNDAMENTALS OF MEASUREMENTS: SI SYSTEM

• General Conference on Weights and Measures

(CGPM) extended MKS & included four other base

units, namely ampere, Kelvin, mole and candela,

that measure electrical current, temperature, amount

of substance and luminous intensity, respectively.

• These seven base quantities assumed to be mutually

independent.

• In 1960 the Eleventh General Conference adopted

the name International System of Units (SI) for the

collection of these seven units.

• The SI is maintained by a small agency in Paris,

International Bureau of Weights andMeasures (BIPM,

for Bureau International des Poids et Mesures).

Length meter m

Mass kilogram kg

Time second s

Amount of substance mole mol

Thermodynamic temperature Kelvin K

Electric current amperes amps

Luminous intensity candela cd

Quantity Name Symbol

FUNDAMENTALS OF MEASUREMENTS: SI BASE UNITS

SI is updated every few years by an international

conference, the General Conference on Weights and

Measures (CGPM, for Conférence Générale des Poids

et Mesures), attended by representatives of all the

industrial countries and international scientific and

engineering organizations.

FUNDAMENTALS OF MEASUREMENTS: SI BASE UNITS

• The International System of Units (SI) identifies

"second" as the base unit for time.

• The second is the duration of 9 192 631 770 cycles of

the radiation associated with a specific transition of the

cesium 133 atom.

• It supersedes the day used originally for time.

• The day is divided in 24 hours, each hour divided in 60

minutes, each minute divided in 60 seconds.

• A second is 1  ⁄ (24 × 60 × 60) of the day.

FUNDAMENTALS OF MEASUREMENTS: SI BASE UNITS

• The SI unit for amount of substance is the mole.

• It has the unit symbol mol.

• One mol of a substance contains an equal number of

elementary entities as there are atoms in 12g of the

isotope carbon-12. (6.022 × 1023) equals 1 molar mass.

• Amount of substance is calculated as the sample mass

divided by the molar mass of the substance.

• The base SI unit for molar mass is kg/mol or g/mol.

• Eg.molar mass of water: M(H2O) ≈ 18 g/mol.

FUNDAMENTALS OF MEASUREMENTS: SI BASE UNITS

• The degree Celsius (°C) scale was devised as

temperature between the freezing and boiling

temperatures of pure water at standard atmospheric

conditions (sea level pressure) into 100 equal parts.

• The basic SI unit of temperature is kelvin (K) which is

an extension of degree Celsius (°C).

• The Kelvin scale is an absolute, thermodynamic

temperature scale using as its null point absolute zero,

the temperature at which all thermal motion stops.

• Unlike the degree Fahrenheit and degree Celsius, the

kelvin is not referred to or typeset as a degree. The

definition implies that absolute zero (0 K) is equivalent

to −273.15 °C (−459.67 °F).

FUNDAMENTALS OF MEASUREMENTS: SI BASE UNITS

TEMPERATURE KELVINDEGREE

CELSIUS

DEGREE

FAHRENHEIT

SYMBOL K °C °F

absolute zero 0. -273.15 -459.67

melting point of ice 273.15 0. 32.

boiling point of water 373.15 100. 212.

human body temperature 310.15 37. 98.6.

TEMPERATURE CONVERSIONS

FROM KELVINS TO KELVINS

°C [°C] = [K] − 273.15 [K] = [°C] + 273.15

°F [°F] = [K] × 9⁄5 − 459.67 [K] = ([°F] + 459.67) × 5⁄9

FROM CELSIUS FROM FAHRENHEIT

[°F] = [°C] × 9⁄5 + 32 [°C] = ([°F] − 32) × 5⁄9

[°F] = [°C] × 1.8 + 32 [°C] = ([°F] − 32) × 0.555

[°C] = ([°F] − 32) / 1.8

DERIVED UNITS OF THE INTERNATIONAL SYSTEM (SI)

• In addition to the seven base units, the General

Conference on Weights and Measures has approved

22 derived units (DU) defined as combinations of the

base units of SI.

• DU covers any algebraic combination of the base

units, but only 22 combinations are approved.

• For the ease of understanding and convenience, 22

SI derived units have been given special names and

symbols.

22 APPROVED DERIVED UNITS OF SIMeasures Derived Unit Derivation Formal Definition

absorbed dose gray (Gy) J/kg m2·s-2

activity becquerel (Bq) /s s-1

catalytic activity katal (kat) mol/s mol·s-1

dose equivalent sievert (Sv) Gy·(multiplier) m2·s-2

electric capacitance farad (F) C/V kg-1·m-2·s4·A2

electric charge coulomb (C) A·s A·s

electric conductance siemens (S) A/V kg-1·m-2·s3·A2

electric potential volt (V) W/A kg·m2·s-3·A-1

electric resistance ohm (omega) V/A kg·m2·s-3·A-2

energy or work joule (J) N·m kg·m2·s-2

force newton (N) kg·(m/s2) kg·m·s-2

frequency hertz (Hz) /s s-1

illuminance lux (lx) lm/m2 cd·sr·m-2

inductance henry (H) Wb/A kg·m2·s-2·A-2

luminous flux lumen (lm) cd·sr cd·sr

magnetic flux weber (Wb) V·s kg·m2·s-2·A-1

magnetic flux density tesla (T) Wb/m2 kg·s-2·A-1

plane angle radian (rad) m·m-1

power watt (W) J/s kg·m2·s-3

pressure pascal (Pa) N/m2 kg·m-1·s-2

solid angle steradian (sr) m2·m-2

temperature degree Celsius (°C) K - 273.15 K

OTHER DERIVED UNITS OF SI

SI derived unit

Derived quantity Name Symbol

area square meter m2

volume cubic meter m3

wave number reciprocal meter m-1

speed, velocity meter per second m/s

acceleration meter per second squared m/s2

mass density kilogram per cubic meter kg/m3

specific volume cubic meter per kilogram m3/kg

dynamic viscosity pascal second Pa·s

surface tension newton per meter N/m

specific heat capacity, specific

entropyjoule per kilogram kelvin J/(kg·K)

absorbed dose rate gray per second Gy/s

OTHER DERIVED UNITS OF SI

Name Symbol Value in SI units

minute (time) min 1 min = 60 s

hour h 1 h = 60 min = 3600 s

day d 1 d = 24 h = 86 400 s

degree (angle) ° 1° = ( /180) rad

liter L 1 L = 1 dm3 = 10-3 m3

metric ton t 1 t = 103 kg

acre a 1 a = 1 dam2 = 102 m2

hectare ha 1 ha = 1 hm2 = 104 m2

curie Ci 1 Ci = 3.7 x 1010 Bq

ångström Å 1 Å = 0.1 nm = 10-10 m

bar bar1 bar = 0.1 MPa = 100 kPa =

1000 hPa = 105 Pa

DEFINITIONS OF SOME IMPORTANT SI UNITS

• The industrial pharmacist should be familiar with the various

systems of units like metric, SI etc..

• Generally, physical properties of matter are expressed by 3

fundamental quantities Length (L) Mass (M) Time (T).

• Other quantities are derived from these units.

• Area = L2 (m2) , Volume = L3 (m3)

• Density (D) is the mass per unit volume M/L3 = ML-3 (g/m3)

• Velocity (V) is the rate of increase in distance= L/T = LT-1

• Acceleration (a) is the rate of increase in velocity= V/T =

LT-1/ T= LT-2

• Force is push or pull which is required to produce a given

acceleration for a body. F= M.a = MLT-2

• Unit of Force is dyne (CGS) or Newton (MKS).

• Work is mechanical form of energy. It is measured by the

magnitude of force and displacement. W = F. D (erg)

• erg is the work done when a force of 1 dyne act through a

distance of 1 cm.

• As erg is very small for practical use, so we use joule.

• 1 absolute joule = 107 erg.

• Power: it is the rate of doing work, and is expressed as

joule/sec or watt.

DEFINITIONS OF SOME IMPORTANT SI UNITS

• Pressure is the force per unit area.

• Usually measured with respect to atmospheric pressure.

• 1 atm. Pressure = 76 cm Hg = 760 mm Hg = 30 inch Hg = 15

psig "pressure square inch gauge“

• Gauge pressure: is the pressure above the atmospheric

pressure. So, the gauge will read zero if the pressure equals

to the atmospheric pressure.

• Absolute pressure = gauge pressure + atmospheric pressure

• If we have a gauge pressure of 10 psig, what will be the

absolute pressure?

• Absolute pressure = 10 "gauge P." + 15 "Atm. P." = 25 psig

DEFINITIONS OF SOME IMPORTANT SI UNITS

• Vacuum: When the pressure inside a system is below

atmospheric pressure, it is frequently expressed as vacuum.

• It is commonly expressed in head of mercury relative to an

atmospheric pressure of 30 inch Hg.

• 25 inch Hg vacuum usually expressed as: 25 "vacuum" / 30

"atmospheric“.

• Absolute pressure = atm. P. – Vacuum P. = 30- 25 = 5 inch Hg.

• During evaporation, drying, and filtration, it is recommended to

maintain the equipment under vacuum, why?

• Reduced pressure minimizes the boiling point of the liquids.

• It reduces the effect of the heat on thermolabile materials.

DEFINITIONS OF SOME IMPORTANT SI UNITS

THANK YOU

FOR

YOUR ATTENTION..