part 9: LIQUIDS

1. Mercury

2. Bromine

Periodic table elements that are liquid in room temperature

1. Possess less kinetic energy than gases

2. Occupy a definite volume

3. Takes the shape of the container that holds it

4. Are considered more denser and less compressible than gases

Characteristics of Liquids

Noyes Whitney Equation

Equation used to determine Rate of Dissolution

Dissolution

The process where a solute in gaseous, liquid, or solid phase dissolves in a solvent to form a solution

Solubility

The measure of ability of a solute to get dissolved in a solvent

• moles/L.soln

• g/L, g/mL

Units of solubility: ______________ or ________________

Pharmacopeial Expression of Solubility

It is the number of milliliters of solvent in which 1 gram of solute will dissolve to make a saturated solution

Very soluble

< 1 part

Freely soluble

1 to 10 parts

Soluble

10 to 30 parts

Sparingly soluble

30 to 100 parts

Slightly soluble

30 to 100 parts

Very slightly soluble

1000 to 10,000 parts

Practically insoluble

> 10,000 parts

1. Nature of solute and solvent

2. Particle size

3. Particle size

4. Pressure

5. Presence of Salts (mostly for proteins)

6. pH

Factors affecting Solubility

Like dissolves like

The greater the similarity between the solute and the solvent the greater the solubility

Low particle size = High Surface area = High Solubility

In particle size:

Low particle size = ____ Surface area = ____ Solubility

Endothermic: High Temperature = High Solubility

In temperature of Solid and Liquid:

Endothermic: ____ Temperature = ____ Solubility

Exothermic: Low Temperature = High Solubility

In temperature of Solid and Liquid:

Exothermic: ____ Temperature = ____ Solubility

Low Temperature = High Solubility

In temperature of Gas:

Low Temperature = ____ Solubility

negligible

Solids and Liquids: The effects of pressure changes on the solubility of solids and liquids are __________

Pressure

Most important factor influencing solubility of a gas in a liquid (Henry’s Law)

High Pressure = High Solubility

In Gas, High Pressure = ____ Solubility

High Solubility

Salting in: + salt = __ Solubility

Low Solubility

Salting out: + salt= __ Solubility

Weak acids or bases

Many drugs are _____ acids or bases

Aqueous solution

The ionized form of a compound will be most soluble in an ____________________

Acidic

WB + __________ aqueous solution = ionized form

Basic

WA + __________ aqueous solution= ionized form

Equilibrium Vapor Pressure (VP)

The pressure of the saturated vapor above the liquid

Equilibrium

Evaporation rate = Condensation rate

mmHg

Unit of Vapor Pressure

23.8 mmHg

Vapor Pressure of Water at 25°C

355.1 mmHg

Vapor Pressure of Water at 80°C

4.61 mmHg

Vapor Pressure of Water at 0°C

Clausius Clapeyron Equation

Cohesion

Attraction between similar molecules

Adhesion

Attraction between unlike molecules

Interfaces

Boundaries of solids, liquids and gases with other solids, liquids or gases

Surface

Used when referring to either a gas-solid or gas-liquid interface

Surface Tension

• The “tension” in the surface

• Force per unit length that must be applied parallel to the surface so as to counterbalance the net inward pull

• Liquid-Gas or Solid-Gas

• SI: N/m

• CGS: dyne/cm

Unit of Surface Tension

Interfacial Tension

Force per unit length existing at the interface between two immiscible phases

• Liquid-Liquid

• Solid-Solid

• Liquid-Solid

N/m (SI) or dyne/cm (CGS)

Unit of Interfacial Tension

1. Capillary Rise Method

2. Dropweight method

3. Du Nouy Ring method

Methods of Surface Tension and Interfacial Tension Determination

Capillary Rise Method

• Oldest method for surface tension determination

• Most accurate method (the surface is undisturbed during the measurement)

• Not suitable for interfacial tension measurement

Higher rise = Lower surface tension= concave meniscus

Adhesion > Cohesion =

Lower rise = Higher surface tension = convex meniscus

Cohesion > Adhesion =

Stalagmometric method

Dropweight method is also known as?

Stalagmometer

Instrument used in Dropweight method

Tensiometer

Instrument used in Du Nouy Ring method

Platimum or Iridium ring

Du Nouy Ring method uses what?

Du Nouy Ring method

Measures both surface and interfacial tension

Surfactants or Amphiphiles

Surface Active Agent is also known as?

Surface Active Agent

Molecules or ions that causes reduction of surface and interfacial tension

Griffin Hydrophilic-Lipophilic Balance System

Number system to establish an HLB range of optimum efficiency for each class of surfactant

Polarity

Each agent is assigned an HLB value or number indicating the substance’s _____________

1-40 (1-20 usual range)

Range of Griffin Hydrophilic-Lipophilic Balance System

Hydrophilic

Higher HLB = ____________

Lipophilic

Low HLB= ____________

1-3

Antifoaming

3-6

w/o emulsifiers

7-9

Wetting agents

8-18

o/w emulsifiers

13-16

Detergents

Solubilizers

15-20

Absorption

• The liquid or gas being absorbed penetrates into the capillary spaces of the absorbing medium

• Example: Sponge and Water

Adsorption

• Adsorption is the process in which materials of one phase (Adsorbate) accumulate or concentrate at the interfacial surface of the other phase (Adsorbent)

• Attraction on the surface

• Example: Activated Charcoal

1. Positive adsorption

2. Negative adsorption

3. Physical adsorption

4. Chemical adsorption

Types of Adsorption

Positive adsorption

When the molecules or ions are partitioned in favor of the SURFACE or INTERFACE

Negative adsorption

Some molecules or ions are partitioned in favor of the BULK of liquid

Physiosorption

Physical adsorption is also known as?

Physical adsorption

• The force of attraction between adsorbate and adsorbent is weak (Van Der Waals)

• Reversible (by increasing Temperature or reducing Pressure)

Desorption

The process by which a physically adsorbed gas is removed

Chemisorption

Chemical adsorption is also known as?

Chemical adsorption

• The force of attraction between adsorbate and adsorbent is chemical bonds

• Irreversible

1. Solid-Gas Adsorption

2. Solid-Liquid Adsorption

Adsorption at Solid Interfaces

1. Removal of objectionable odors (from rooms and food)

2. Operation of gas masks

3. Measurement of the dimensions of particles in a powder

Solid-Gas Adsorption

1. Decolorizing solutions

2. Adsorption chromatography

3. Detergency

4. Wetting

Solid-Liquid Adsorption

1. Wetting

2. Detergency

Adsorption at solid surfaces is involved in the phenomena of __________ and __________

Wetting

An adsorption process in which an intimate contact of the solids with liquid phase is achieved

Low contact angle

_____ contact angle: Adhesive>Cohesive

High contact angle

_____ contact angle: Cohesive>Adhesive

Complete wetting

0° = __________ wetting

No wetting

180° = __________ wetting

7-9

Wetting agents are surfactants with HLB values of ___ - ___

Wetting agents

aid in attaining intimate contact between solid particles and liquids

Detergency

A phenomenon in which surfactants are used to remove foreign materials from solid surfaces

Detergents

will reduce the surface tension and aid in wetting the surface and the dirt