68 Chapters
Medium 9789383828432

Ch_19_F

P.S.Sona Laxmi Publications PDF

78 A Practical Manual of Pharmaceutical Engineering simple sedimentation. Separation is happened under gravity depending upon the size as well as the density of the particles. So sedimentation method can be used for determining the size of the particle settled.

Several methods are available based on sedimentation for the size separation and particle size determination. They are hydrometer method, pipette method and balance method. Andreasen apparatus works under the principle of pipette method. The particle size in the sub sieve range may be obtained by sedimentation as expressed in Stoke�s law,

V = h/t =

dsJ 2 ( r s - r0 ) g

18 h 0

� (Eq: 19.1)

Or

@It =

18 h 0 D / ( r s - r 0 ) g J

� (Eq: 19.2)

Where,

V h dst rs, r0 h0

= Rate of settling (m/s)

= Distance of fall within time (t)

= Mean diameter of particle based on the velocity of settling

= Density of particle and water (kg/m3)

= Viscosity of medium (Poise)

The particle diameter corresponding to various time intervals is calculated from Stoke�s law.

The residue or dried sample obtained at a particular time is the weight fraction having particle of size less than that size obtained from Stoke�s law. Hence each sample is therefore called as weight undersize. Add up the successive weight undersize (expressed in %). This is then plotted on log probability scale (log normal) against particle diameter (log scale) and the geometrical mean diameter d�g can be determined from the reference point i.e., 50% on the probability scale and geometrical standard deviation sg can be determined from the slope. The other statistical parameters can be determined from the equations, log dln (Length number mean diameter) log dsn (Surface number mean diameter) log dvn (Volume number mean diameter) log dvs. (Volume surface mean diameter) log dwm (Weight momentum mean diameter)

See All Chapters
Medium 9789383828432

Ch_24_F

P.S.Sona Laxmi Publications PDF

Determination of Temperature Humidity Index—THI 97

EXPERIMENT

24

DETERMINATION OF TEMPERATURE

HUMIDITY INDEX—THI

AIM

To determine the temperature humidity index of the atmosphere.

REQUIREMENTS

Wet bulb and dry bulb thermometers (Mansion type)

(1)

Water

PRINCIPLE

Temperature humidity index is a number that express the degree of discomfort of the average individual due to the atmospheric temperature and relative humidity.

If the atmospheric temperature increases, the flow of heat from the body to the surroundings decreases. Increased humidity is also a reason for the lowering the air flow from body to atmosphere (because of the slow evaporation of sweat from the body). So the temperature and humidity determines the human comfort. If the humidity is high the feel of �hot� is more compared to the less humid area of same dry bulb temperature. THI can be determined by the following equation,

THI = (0.4 X Wet bulb temperature + Dry bulb temperature) + 15

THI

Atmosphere

<70

Comfortable

70 -80

Causes discomfort to some individuals

See All Chapters
Medium 9789383828432

Ch_15_F

P.S.Sona Laxmi Publications PDF

60 A Practical Manual of Pharmaceutical Engineering

EXPERIMENT

OF

15

DETERMINATION OF EFFECT

TIME ON GRINDING OPERATION

OF A BALL MILL

AIM

To study the effect of time on grinding rate of a ball mill.

REQUIREMENTS

Ball mill

(1)

Balls (same size and density)

(12)

Sieve 120 or 85 mesh

(1)

Weighing balance

(1)

Butter paper

(1)

Spatula

(1)

Weighing box

(1)

Sugar

PRINCIPLE

Ball mill consist of a horizontally rotating hollow cylinder shape with the length slightly greater than its diameter. The mill is partially filled with balls of steel or pebbles. In ball mill size reduction happens by impact and attrition. The speed of rotation is so important, as the slow speed of rotation contribute only a sliding action and high speed a centrifugal action. At both this speed, no significant size reduction happens. The optimum speed of a ball mill is a speed at which the balls just begins to centrifuge within the mill contributing a cascading action and hence a significant size reduction.

The optimum speed of rotation can be determined by the following equation,

See All Chapters
Medium 9789383828432

Ch_41_F

P.S.Sona Laxmi Publications PDF

156 A Practical Manual of Pharmaceutical Engineering

EXPERIMENT

41

VACUUM DISTILLATION—EFFECT OF

VACUUM ON DISTILLATION OF

ASPIRIN REACTION MIXTURE

AIM

To perform the vacuum distillation at varying pressure.

To find out the rate of distillation at varying pressure (vacuum).

To determine the effect of vacuum on the distillation of thermo labile drug (aspirin).

REQUIREMENTS

Vacuum distillation assemble (Vacuum pump, claisen flask, Round bottom flask, Measuring cylinder, Separating funnel, Stop cock, Adaptors, Bend tubes Thermometer, Condenser)

Heating mantle

(1)

Tripod stand

(2)

Burette stands

(3)

Ethanol

Water

Aspirin

PRINCIPLE

Vacuum distillation is a distillation process used for materials that have very high boiling-points or are likely to decompose at their boiling-points. Vacuum distillation is a distillation at reduced pressure. Since the boiling point of a compound is lower at a lower external pressure, the compound will not have to be heated to as high a temperature in order for it to boil. The vacuum is provided either by a water aspirator or by a mechanical pump, and the vacuum so formed causes the materials being heated to boil at a temperature lower than they would under normal atmospheric pressure. This enables distillation to take place at lower temperatures. A reliable vacuum

See All Chapters
Medium 9789383828432

Ch_6_F

P.S.Sona Laxmi Publications PDF

Determination of Pressure Difference during Liquid Flow Using Simple Manometer

EXPERIMENT

DETERMINATION

23

6

PRESSURE

DIFFERENCE DURING LIQUID FLOW

USING SIMPLE MANOMETER

OF

AIM

To determine the pressure difference in a flow of liquid through a pipe with the help of simple Utube manometer.

REQUIREMENTS

Orifices meter or venturi meter assemble

(1)

Pump

(1)

Manometer

(1)

Water

PRINCIPLE

A manometer, when used properly, is a very accurate instrument for the determination of pressure difference during fluid flow. The U-type manometer is a primary standard due to its inherent accuracy and simplicity of operation. The manometer has no moving parts subject to wear, age, or fatigue. U tube Manometer consists of two limbs which are attached to the pipe through which the fluid is flowing. Both the limbs are filled with mercury in equal quantity. If there is no pressure difference both the limbs show same height of the mercury level on the scale. If any pressure difference occurs between the limbs, mercury level in the limb will differs and shows increased or decreased scale readings. The pressure difference can be determined by the equation,

See All Chapters

See All Chapters