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PHA6113 > [PHA6113 lec] Micromeritics > Flashcards

[PHA6113 lec] Micromeritics Flashcards

1
Q

The science and technology of small particles

A

Micromeritics

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2
Q

Most accurate method of determining particle size

A

Optical Microscopy or Microscopic Method

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3
Q

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

A

True

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4
Q

Unit of particle size

A

Micrometer or micron (µm or µ)

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5
Q

1 µm or µ

A

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

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6
Q

1 millimicron (mµ)

A

1 nanometer (nm) = 10^-9 m

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7
Q

Simplest method of determining particle size

A

Sieving (USP Method)

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8
Q

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

A

Sieving (USP Method)

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9
Q

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

A

Sieving (USP Method)

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10
Q

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

A

Particle Volume Measurement

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11
Q

Makes use of the Andreasen apparatus

A

Sedimentation Method

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12
Q

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

A

Sedimentation Method

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13
Q

Law that expresses the rate of settling

A

Stoke’s Law

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14
Q

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

A

False, not applicable

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15
Q

Formula for Stoke’s Law

A

CHECK YOUR HANDOUT RIGHT NOW

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16
Q

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

A

CHECK YOUR HANDOUT RIGHT NOW

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17
Q

Most powders have a porosity between _______?

A

30-50%

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18
Q

Closest or rhombohedral packing arrangement

A

Low porosity - 26%

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19
Q

Open or cubic packing arrangement

A

Highest porosity - 48%

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20
Q

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

A

True Density

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21
Q

Formula of True Density

A

ρ = W/Vp

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22
Q

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

A

Bulk or apparent density

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23
Q

Formula of Apparent Density

A

ρ = W/Vb

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24
Q

Reciprocal of Apparent Density

A

Bulkiness

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25
Q

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

A

Granule density

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26
Q

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

A

Equal

27
Q

Based on bulk density, powder may be?

A

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

b. Heavy - high apparent density, small bulk volume and low porosity

28
Q

Powders may be free-flowing or cohesive depending on?

A

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

29
Q

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

A

Elongated or Flat particles

30
Q

Closely packed, low porosity, high density, free flowing

A

Nearly spherical particles

31
Q

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

A

Coarse Dispersions

32
Q

3 Types of Coarse Dispersions

A
  1. Suspensions
  2. Emulsions
  3. Semi-solids
33
Q

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

A

Suspension

34
Q

Factors affecting sedimentation based on Stoke’s Law

A
  1. Particle size and density - larger particles sediment rapidly compared to smaller particles
  2. Viscosity of medium - inversely proportional to the sedimentation rate
35
Q

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

A

Emulsions

36
Q

2 Types of Emulsions

A

O/W and W/O

37
Q

Methods of Preparing Emulsions

A
  1. Continental or Dry Gum
  2. English or Wet Gum
  3. Bottle or Forbes
  4. In-situ Soap
38
Q

Methods of detecting type of emulsion

A
  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
39
Q

Forms of instability

A
  1. Creaming and sedimentation
  2. Aggregation and coalescence
  3. Inversion
40
Q

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

A

Creaming

41
Q

[Forms of instability]
Downward movement of the particles

A

Sedimentation

42
Q

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

A

Aggregation or flocculation

43
Q

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

A

Coalescence

44
Q

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

A

Inversion

45
Q

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

A
  1. Addition of electrolyte
  2. Changing the phase volume ratio
46
Q

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

A

Gels

47
Q

Gel wherein the coherent matrix is liquid

A

Jelly (ex. table jellies)

48
Q

Gel when the liquid is removed and only the framework remains

A

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

49
Q

3 Changes observed in gels

A
  1. Syneresis
  2. Swelling
  3. Imbibition
50
Q

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

A

Syneresis

51
Q

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

A

Swelling

52
Q

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

A

Imbibition

53
Q

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

A

Colloidal Dispersion

54
Q

Colloidal dispersion of solid in liquid

A

Sol

55
Q

Colloidal dispersion of solid or liquid in gases

A

Aerosol

56
Q

Types of Colloidal System

A
  1. Lyophilic colloids
  2. Lyophobic colloids
  3. Association of amphiphilic colloids
57
Q

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

A

Lyophilic colloids (ex. gelatin, acacia)

58
Q

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

A

Lyophobic colloids (ex. gold, silver, sulfur)

59
Q

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

A

Association or amphiphilic colloids (ex. surface active agents)

60
Q

Methods of Purifying Colloids

A
  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
61
Q

Properties of Colloids

A
  1. Optical Property
  2. Kinetic Property
  3. Electrical Property
62
Q

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

A

Tyndall Effect

63
Q

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

A

Brownian Movement

64
Q

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

A

Electrical Property

PHA6113 (3 decks)

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