[PHA6113 lec] Micromeritics

Question 1

The science and technology of small particles

Answer 1

Micromeritics

Question 2

Most accurate method of determining particle size

Answer 2

Optical Microscopy or Microscopic Method

Question 3

T or F: The microscope eyepiece is fitted with a micrometer by which the size of particles may be estimated

Answer 3

True

Question 4

Unit of particle size

Answer 4

Micrometer or micron (µm or µ)

Question 5

1 µm or µ

Answer 5

10^-6 m, 10^-4 cm, 10^-3 mm

Question 6

1 millimicron (mµ)

Answer 6

1 nanometer (nm) = 10^-9 m

Question 7

Simplest method of determining particle size

Answer 7

Sieving (USP Method)

Question 8

This method utilizes a series of standard sieves calibrated by the National Bureau of Standards

Answer 8

Sieving (USP Method)

Question 9

This technique involves size classification followed by the determination of the weight of each fraction

Answer 9

Sieving (USP Method)

Question 10

This method makes use of a coulter counter in determining the particle volume distribution of material suspended in an electrolyte-containing solution

Answer 10

Particle Volume Measurement

Question 11

Makes use of the Andreasen apparatus

Answer 11

Sedimentation Method

Question 12

This method employs the settling of particles in a liquid of a relatively low density under the influence of a gravitational or centrifugal field

Answer 12

Sedimentation Method

Question 13

Law that expresses the rate of settling

Answer 13

Stoke’s Law

Question 14

T or F: Stoke’s law is applicable for particles which aggregate or clump together

Answer 14

False, not applicable

Question 15

Formula for Stoke’s Law

Answer 15

CHECK YOUR HANDOUT RIGHT NOW

Question 16

[Derived Properties of Powders]
Formula for Porosity or Voids (Є)

Answer 16

CHECK YOUR HANDOUT RIGHT NOW

Question 17

Most powders have a porosity between _______?

Answer 17

30-50%

Question 18

Closest or rhombohedral packing arrangement

Answer 18

Low porosity - 26%

Question 19

Open or cubic packing arrangement

Answer 19

Highest porosity - 48%

Question 20

Density of the actual solid and is exclusive of the voids and interparticle pores

Answer 20

True Density

Question 21

Formula of True Density

Answer 21

ρ = W/Vp

Question 22

Determined from the bulk volume and the weight of a dry powder in a graduated cylinder

Answer 22

Bulk or apparent density

Question 23

Formula of Apparent Density

Answer 23

ρ = W/Vb

Question 24

Reciprocal of Apparent Density

Answer 24

Bulkiness

Question 25

Determined by displacement of mercury which does not penetrate at ordinary pressure into pores smaller than about 10µm

Answer 25

Granule density

Question 26

What is the relationship between true density and granule density when the solid is non-porous?

Answer 26

Equal

Question 27

Based on bulk density, powder may be?

Answer 27

a. Light - low apparent or bulk density, large bulk volume and high porosity b. Heavy - high apparent density, small bulk volume and low porosity

Question 28

Powders may be free-flowing or cohesive depending on?

Answer 28

a. Particle size - as particle size increases, flow is facilitated b. Shape c. Porosity d. Density

Question 29

Loosely packed, high porosity, low density, does not flow freely

Answer 29

Elongated or Flat particles

Question 30

Closely packed, low porosity, high density, free flowing

Answer 30

Nearly spherical particles

Question 31

Dispersions in which the size of the dispersed particle is 0.5 µm – 10 µm

Answer 31

Coarse Dispersions

Question 32

3 Types of Coarse Dispersions

Answer 32

1. Suspensions 2. Emulsions 3. Semi-solids

Question 33

Coarse dispersion in which insoluble solid particles are dispersed in a liquid medium

Answer 33

Suspension

Question 34

Factors affecting sedimentation based on Stoke's Law

Answer 34

1. Particle size and density - larger particles sediment rapidly compared to smaller particles 2. Viscosity of medium - inversely proportional to the sedimentation rate

Question 35

Dispersed system of at least two immiscible liquid phases, one of which is dispersed as globules in other liquid phase

Answer 35

Emulsions

Question 36

2 Types of Emulsions

Answer 36

O/W and W/O

Question 37

Methods of Preparing Emulsions

Answer 37

1. Continental or Dry Gum 2. English or Wet Gum 3. Bottle or Forbes 4. In-situ Soap

Question 38

Methods of detecting type of emulsion

Answer 38

1. Dilution test - when oil is added to an o/w emulsion or water is added to a w/o emulsion = separation is apparent 2. Conductivity test - o/w has high conductivity while w/o has no or low conductivity 3. Dye-solubility test - water soluble dye is soluble in o/w while oil soluble dye is soluble in w/o

Question 39

Forms of instability

Answer 39

1. Creaming and sedimentation 2. Aggregation and coalescence 3. Inversion

Question 40

[Forms of instability] Upward movement of the dispersed droplets relative to the continuous phase

Answer 40

Creaming

Question 41

[Forms of instability] Downward movement of the particles

Answer 41

Sedimentation

Question 42

[Forms of instability] Dispersed droplets come together but do not fuse

Answer 42

Aggregation or flocculation

Question 43

[Forms of instability] Complete fusion of droplets leading to the ultimate separation of the 2 immiscible phases

Answer 43

Coalescence

Question 44

[Forms of instability] Change from w/o to o/w and vice-versa

Answer 44

Inversion

Question 45

[Forms of instability] Inversion is brought about by 2 things

Answer 45

1. Addition of electrolyte 2. Changing the phase volume ratio

Question 46

A solid or semisolid system of at least 2 constituents, consisting of a condensed mass enclosing and interpenetrated by a liquid

Answer 46

Gels

Question 47

Gel wherein the coherent matrix is liquid

Answer 47

Jelly (ex. table jellies)

Question 48

Gel when the liquid is removed and only the framework remains

Answer 48

Xerogel (ex. gelatin sheets, tragacanth ribbon, and acacia tears)

Question 49

3 Changes observed in gels

Answer 49

1. Syneresis 2. Swelling 3. Imbibition

Question 50

[Changes in Gels] Natural shrinking of a gel after standing for some time with pressing out some of the liquid

Answer 50

Syneresis

Question 51

[Changes in Gels] Taking up of liquid by a gel with an increase in volume

Answer 51

Swelling

Question 52

[Changes in Gels] Taking up of liquid without increase in volume

Answer 52

Imbibition

Question 53

Heterogeneous system in which the mean particle size of the dispersed phase is 1 nm to 0.5 µm

Answer 53

Colloidal Dispersion

Question 54

Colloidal dispersion of solid in liquid

Answer 54

Sol

Question 55

Colloidal dispersion of solid or liquid in gases

Answer 55

Aerosol

Question 56

Types of Colloidal System

Answer 56

1. Lyophilic colloids 2. Lyophobic colloids 3. Association of amphiphilic colloids

Question 57

[Types of Colloidal System] System containing colloidal particles that interact to an appreciable extent with the dispersion medium

Answer 57

Lyophilic colloids (ex. gelatin, acacia)

Question 58

[Types of Colloidal System] Materials which have very little attraction for the dispersion medium

Answer 58

Lyophobic colloids (ex. gold, silver, sulfur)

Question 59

[Types of Colloidal System] Small molecules in dilute solution tend to associate into aggregate (micelles) which are of colloidal dimensions

Answer 59

Association or amphiphilic colloids (ex. surface active agents)

Question 60

Methods of Purifying Colloids

Answer 60

1. Dialysis - diffusion through a membrane of parchment cellophane or collodion which removes molecules or ions which pass through 2. Ultrafiltration - filtration through ultrafilters prepared from collodion impregnated with and dried for a long time, allowing passage of all substances EXCEPT colloidal particles

Question 61

Properties of Colloids

Answer 61

1. Optical Property 2. Kinetic Property 3. Electrical Property

Question 62

Optical property of Colloids which refers to the scattering of light produced when a strong beam of light is passed through a colloidal solution

Answer 62

Tyndall Effect

Question 63

Kinetic property of Colloids which refers to the random movement of the colloidal particles

Answer 63

Brownian Movement

Question 64

Property of Colloids which refers to the presence of charge on the surface of particles

Answer 64

Electrical Property