Mixing Flashcards
What is meant when a sample is homogeneous
it’s mixed in which the composition is uniform throughout
Why is homogeneity important
so that each dose is identical, can be identically manufactured. Ensures api is +_ 5%
What are the three types of mixtures
Positive, negative and neutral
What is a positive mixture
A mixture in which the substances completely mix spontaneously. Energy is required to separate the substances. Water and ethanol
What is a negative mixture
A mixture where the component do not stay mixed and separate spontaneously. Energy is required to keep the components mixed. E.g. water and oil.
what does miscible mean
When a substance is able to mix and form a homogenous mixture
What does immiscible mean
when substance is unable to mix and for and a homogeneous mixture
What is a neutral mixture
a mixture in which the components do not separate or mix spontaneously. However energy is required to mix but components stay mixed,
What are the the three ways of mixing liquids
Bulk, turbulent and molecular
What is bulk mixing
redistributing large amounts of liquids. Occurs in a short period of time
What is turbulent mixing
Mixing liquids by the redistribution of liquids by constantly changing velocity
What is molecular mixing
mixing liquid Molecules by going down their concentration gradient
What are the three types of solid mixing
convective, shear and diffuse
What is convective mixing
redistribution of large amounts of particles
What is shear mixing
velocity difference between layers cause them to slide over each other
What is diffuse mixing
particles move from a high concentration into a low where there are air particles.
What are the two types of mixtures
random and perfect
Why is random mixture the best Attainable mixture
the probability of selecting a specific particle is the same throughout the whole mixture.
What is the equation used to determine if a mixture is adequate
σR = √p(1-p)/N
σR= theoretical standard deviation of a random mixture
P=proportion of drug in mixer
N= total number of particles in the mixture
How is the σR used to determine if a mixture is adequate
σ/σR.
σR= theoretical standard deviation of mixture
σ= sample standard deviation of mixture
>1 then not mixed properly
=1 then adequate mixture
<1 mixed too much, is lax
What is the reverse process of mixing
segregation
What is the difference between segregation and demixing
demixing is unwanted separation of a mixture while segregation is intended.
What properties will allow easier segregation
particles are different size and density and if they’re spherical
What are the three methods of segregation
Percolation, trajectory and elutriation
What is percolation segregation
when smaller particles are serrated using voids.
What is trajectory separation
when particles are allowed to flow out of a tube. Larger particle go further as they’re heavier so have more momentum
What is elutriation segregation
When the least dense solids end up on top after movement stops.
How to reduce segregation
Minimise vibrations, particles are the same size and density
