Physical Pharmacy: Association Colloids in Colloidal Dispersions

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What is the characteristic of amphiphiles or surface-active agents?

Having two distinct regions of opposing solution affinities within the same molecule or ion.

What occurs when the concentration of amphiphiles is increased in a liquid medium?

Aggregation occurs over a narrow concentration range.

What is the term for the aggregates formed by amphiphiles?

Micelles

Why are micelles considered colloidal particles?

Because their diameter is of the order of 50 Å. Signup and view all the answers

What is the term for the type of colloids formed by amphiphiles?

Association colloids Signup and view all the answers

What is the characteristic of the dispersed phase in a lyophilic colloidal dispersion?

Large organic molecules that are solvated and lie within the colloidal size range Signup and view all the answers

What is the effect of high concentrations of electrolytes on lyophilic colloidal dispersions?

They can be salted out due to desolvation of lyophilic molecules Signup and view all the answers

What is the main difference between lyophilic and lyophobic colloidal dispersions in terms of interaction between particles and dispersion medium?

Lyophilic dispersions have strong interaction (solvation) whereas lyophobic dispersions have little or no interaction Signup and view all the answers

Why do lyophobic colloidal dispersions require special procedures to produce?

Because they do not disperse spontaneously Signup and view all the answers

What is the effect of electrolytes on the stability of lyophobic colloidal dispersions?

They can destabilize the dispersion due to neutralization of the charge on the particles Signup and view all the answers

What is the characteristic of the particles in a lyophobic colloidal dispersion?

They are usually inorganic, unsolvated, and symmetric Signup and view all the answers

What is the characteristic of lyophilic colloids that enables them to exhibit a protective effect?

They exert a protective effect due to the formation of colloidal aggregates that are spontaneously formed when the concentration of amphiphile exceeds the critical micelle concentration. Signup and view all the answers

What is the critical micelle concentration, and how does it relate to the formation of micelles?

It is the concentration of amphiphile above which micelles are formed spontaneously, and below which the amphiphile molecules exist as individual units. Signup and view all the answers

How does the addition of electrolytes to an aqueous solution of an amphiphile affect the critical micelle concentration?

The addition of electrolytes reduces the critical micelle concentration, making it easier to form micelles. Signup and view all the answers

What is the effect of increasing the concentration of an amphiphile on the viscosity of the system?

The viscosity of the system increases as the concentration of the amphiphile increases, due to the formation of more and larger micelles. Signup and view all the answers

What is the term for the phenomenon where the addition of salt to an aqueous solution of an amphiphile causes the precipitation of the amphiphile?

Salting out Signup and view all the answers