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Pharm Y2S2 > Mixing > Flashcards

Mixing Flashcards

1
Q

Define positive mixing.

A

Components mix spontaneously with no energy required, irreversible by diffusion

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2
Q

Give an example of components that exhibit positive mixing.

A

Two miscible liquids

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3
Q

Define negative mixing.

A

Components tend to separate, requires constant energy input to maintain desired dispersion

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4
Q

Give an example of components that exhibit negative mixing.

A

Suspension with low viscosity solution

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5
Q

Define neutral mixing.

A

No tendency for components to mix or separate spontaneously, possible to separate with energy

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6
Q

Give an example of components that exhibit neutral mixing.

A

Two solid powders

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7
Q

What are random mixtures?

A

Components are perfectly mixed

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8
Q

What is ordered mixing?

A

Components are not completely independent of each other and give a spontaneous degree of order in the mix

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9
Q

What is the scale of scrutiny?

A

Measure used to determine the extent of random mixing to have occurred, dependent on sample size

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10
Q

What mixer should be used for potent drugs?

A

Diffuse mixer

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11
Q

What mixer should be used for particles that tend to aggregate?

A

High shear mixer

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12
Q

Describe the features of convection mixing?

A

Macroscopic
Relatively quick
Extended time need for random mixing
Transfer of particle group through powder bed

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13
Q

Describe the features of shear mixing?

A

Interface mixing
Flows one layer of material over another
Results in moving layers at different speeds

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14
Q

Describe the features of diffusion mixing?

A

Allows movement of individual particles for true random mix
Powder bed is forced to move
Generates space between particles

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15
Q

Describe the features of tumbling mixers?

A

Mix blending granules or free flowing powders
Rotates about an axis at controlled speed
Powder weight 50g-100kg
Occupies approximated half of the mixer volume

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16
Q

What is bulk transport?

A

Quick degree of mixing, movement of large amounts of material in the mix

17
Q

Describe the features of turbulent mixing?

A

Highly effective

Volumes are forced to move with constant change in speed and direction

18
Q

What are turbine mixers used for?

A

Viscous fluids

19
Q

How can segregation be minimised?

A 
Similar size of drug and excipients
Control shape
Reduce mechanical stress
Granulate mixture
Use of ordered mixture

Pharm Y2S2 (26 decks)

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