This document discusses solubility expressions and provides definitions of key terms related to solubility. It defines solubility as the maximum amount of solute that will dissolve in a given amount of solvent at a given temperature. The USP generally expresses drug solubility in terms of the volume of solvent required to dissolve 1 gram of drug. Several common units for expressing solubility are described, including percentage, molarity, molality, and normality. Formulas for calculating each of these units are provided. The document concludes by mentioning the USP and BP solubility criteria.

1. PHYSICAL PHARMACEUTICS-I
(BP 302T)
TOPIC 1 : SOLUBILITY EXPRESSIONS
Presented by:
Nitin tyagi
Associate professor
Umalok college of pharmacy

2. Solubility Of Drugs
Solubility
• It is a Quantitative term.
• It defines the intrinsic property of a material.
Solubility depends upon
Physical, chemical properties of the solute and the solvent
Conditions like temperature, pressure and pH of the solution.

3. Define solubility
The maximum amount of solute or substance that will dissolve in
given amount of solvent at a given temperature.
The USP/NF generally expresses the solubility in terms of the volume
of solvent required to dissolve 1 gram of the drug at a specified
temperature.
The spontaneous interaction of two or more substances to form a
homogeneous molecular dispersion.
• A solute is any substance which can be either
solid or liquid or gas dissolved in a solvent.
• A solvent is the medium in which components are
dissolved.

4. Now what is a Solution?
It is a mixture of two or more components that forms a homogenous
mixture
Saturated solutions are the solution in which the dissolved solute is in
equilibrium with the solvent phase, at a definite temperature.
An unsaturated solution is the solution containing the dissolved solute
in concentration below that is necessary for saturation, at a definite
temperature
A supersaturated solution is the one that contains more of the dissolved
solute than that it would normally contain at a definite temperature

5. Solubility Expression
The USP describes the solubility of drugs as parts of solvent required to
dissolve one part of solute.
It is expressed quantitatively as :
oMolality
oMolarity
oPercentage

6. Percentage term used in solubility
1. % W/W = Percent Weight by Weight → No. of gram of solute dissolved
in 100 gram of solution.
2. % V/V = Percent volume by volume → No. of ml of solute dissolved in
100 ml of solution.
3. % W/V = Percent Weight by volume → No. of gram of solute dissolved
in 100 ml of solution.

7. Molarity:It is defined as the number of moles (or gram molecular weight) of solute
dissolved in 1 litre of solution.
Molality:It is defined as thmoles of solute dissolved in 1000 g of solvent.
Mole fraction:It is the ratio of moles of solute to total mass of solution plus
solvent.
Normality:The No. of gram or mole equivalents of solute present in one litre of a
solution.
When we say equivalent, it is the No. of moles of reactive units in a compound.

8. Normality Formula
Normality = Number of gram equivalents of solute × [volume of
solution in litres]-1
Number of gram equivalents = weight of solute(gm) × [Equivalent
weight of solute]-1
N = Weight of Solute (gram) ×1000×[Equivalent weight × Volume (L)
]-1
Equivalent weight= Molar mass×n-1 *Where n is number of hydrogen atoms in an acid or hydroxide atoms in a base.

9. USP & BP Solubility Criteria

10. Thank you