2. Solutions
‐ solutions may be prepared from any combination of solid,
liquid or gas, the three states of matter
‐ Liquid preparations that contain one or more soluble
chemical substances dissolved in a suitable solvent or
mixture of mutually miscible solvents
‐Homogenous mixture that is prepared by dissolving a solid,
liquid or gas in another liquid and represents a group of
preparations in which the molecules of the solute or
4. Types of Solutions
1.Solid Solution – the solvent is solid
a. Solid in solid
Example: Cu + gold= 12 karat yellow gold
b. Liquid in solid
Example: Hg dissolved in Ag = amalgam
c. Gas in solid
Example: air dissolved in soap = floating soap
2.Liquid Solution – the solvent is liquid
a. solid in liquid
Ex: salt in water
b. Liquid in liquid
5. Ex: alcohol and water
c.Gas in liquid
Ex: carbonated beverages
6. 3.Gaseous Solutions – the solvent is gas
a. Solid in gas
Example: sulfur in air
b. Liquid in gas
Example: water vapor in air
c.Gas in gas
Example: oxygenated air
Factors affecting the “rate” of solubility
1. Particle size – an increase in surface area to the solvent
will decrease the rate of solution. So the particle size
should be reduced by comminution before it is
dissolved.
7. 2. Agitation – increases the rate of solution by removing
from the surface of the solute. The more concentrated
solution around it the less concentrated the solvent.
8. 3.Temperature
heating a liquid also causes solution to take place more
rapidly by increasing the frequency which solvent
molecules collide with the surface of the dissolving
mixture
Factors Affecting Solubility of Solute
1. Temperature
Endothermic reaction – The process of solution
where heat is applied and absorption of the heat
9. takes place in the solutes, this increase in
temperature will cause more of the solute to go
into solution.
10. Exothermic reaction – solute gives off heat during
the process of solution; solubility is decreased with
an increase in temperature.
Example: more soluble in cold than hot water
Methyl cellulose and calcium salts such as
Ca(OH)2
2.Molecular Structure
The general rule: “like dissolves like”
3.Effects of other substance
Example: Iodine is very slightly soluble in water but
when added to a concentrated solution of KI dissolves
immediately.
4.pH – Many of the organic substances which are used
medicinally are either weak acids or weak bases. And
their aqueous solubility depends upon the pH of the
12. Examples of Weak Bases
• Alkaloids –
atropine,codeine,
morphine
Examples of Weak
Acids
• Barbiturates
13.
14. Relative Terms of Solubility
Terms Parts of solvents
required per parts of
solute
Very soluble Less than one
Freely soluble 1 – 10
Soluble 10 – 30
Sparingly soluble 30 – 100
Slightly soluble 100 – 1000
Very slightly soluble 1000 – 10,000
18. Inorganic Molecules
1. Monovalent cation and anion of an ionic compound are
generally water soluble
Examples: NaCl, LiBr, KI, NH4NO3
2. Only one of the two ions is monovalent – compounds are
water soluble
Examples: BaCl2, MgI2, Na2SO4, Na3 PO4
3. Both ions are multivalent ‐ poor water soluble.
Examples: CaSO4, BaSO4, BiPO4
Exceptions: ZnSO4 and FeSO4
19. 4. Common salts of alkali metals are usually water soluble
Exception: Li2CO3
20. 5. NH4 and quaternary NH4 salts are water soluble
21. Organic Molecules
1. Molecules having 1 polar functional group –
soluble to the the total lengths of 5C’s
2. Molecules having branched chains are more soluble
than the corresponding straight‐chain compound.
3. Water solubility decreases with increase in MW
4. Increased structural similarity between solute and
solvents accompanied by increase solubility.
