Definition, classification of solution, Crystalloids and Colloids, Dialysis, Diffusion, Osmosis, Adsorption, Surface tension

1. Solutions, Crystalloids , Colloids,
Dialysis, Diffusion, Osmosis, Adsorption,
Surface tension, Viscosity, Isotopes
Dr. Ifat Ara Begum
Associate Professor
Department of Biochemistry
Dhaka Medical College, Dhaka

2. Introduction to Solution

3. What is Solution?
 It is a homogenous mixture
of 2 / more substances
distributed uniformly
among each other.
 The substances may be
solid / liquid / gasses
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4. What is Matter?
 In classical physics and general
chemistry, matter is any substance
that has mass and takes up space by
having volume.
 Matter exists in various states (also
known as phases).
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 Homogeneous mixture / solution:
 Components of the mixture form a single phase.
 Shows all through same composition
 Particles are evenly distributed
 Very stable, i.e. its particles do not settle, or
separate.
 Example: Salt water, sugar water (i.e. any
crystalloidal solution)
 Heterogeneous mixture / solution:
 Components of the mixture shows
different composition in different
parts of the total mixture
 Particles are not evenly distributed
 Example: Solution of protein in
water
(Any colloidal solution)

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Solute:
 The component of a solution
which forms the minor portion of
that solution
 They are held in the solution by
the solvent
 Solid / Liquid / Gas
 Example: In 0.9% NaCl solution,
NaCl is the solute
Solvent:
 The component of a solution which
forms the larger portion of that solution
Physical state of solvent is same as
the physical state of the solution
 Solid / Liquid / Gas
 Example: In 0.9% NaCl solution,
water is the solvent

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10. Concentration of solution
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Way of expression of
concentration of a solution
What does it mean Example
Percentage by weight
(w/w)
gm of solute per 100 gm of
solution
5% dextrose (w/w)
Percentage by volume
(w/v)
or
(v/v)
gm of solute per 100 ml of
solution
Or
ml of solute per 100 ml of
solution
5% dextrose (w/v)
Or
5% alcohol (v/v)

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Way of expression of
concentration of a solution
What does it mean Example
Molarity Number of mole (mol) of
solute per liter of solution
5 molar glucose
solution
Molality Number of mole (mol) of
solute per kg of solvent
5 molal glucose
solution
Normality Number of equivalent (Eq) of
solute per liter of solution
3N HCl solution

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Way of expression of
concentration of a
solution
What does it mean Example
Osmolarity Number of osmole (Osm) of
solute per liter of solution
2 osmolar glucose
solution
Osmolality Number of osmole (Osm) of
solute per kg of solvent
3 osmolal glucose
solution

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Mole: (Mol or mol)
 Molecular weight or atomic weight
of a substance expressed in gram
 gm-MW (if compound)
or gm-AW (if element)
Equivalent: (Eq or eq)
 The equivalent weight of a substance
expressed in gram
 Equivalent weight = MW or AW / valency
[ If acid, Eq = MW / Number of “H” atoms]
 So, Eq = Mole / Valency
Osmole: (Osm or osm)
 Amount of osmotically active substances in gram, which in 1 liter solution with water,
exerts an OP of 22.4 atmosphere (22.4 x 760 mm Hg) & depresses the freezing point of
water by 1.86 degree C.
 Osmole = Mole / Number of particle given by each molecule in solution by dissociation

17. “Molality is preferred to molarity”
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Molarity Molality
Mole / Liter Mole / kg
Is affected by changes in temperature Is not affected by changes in temperature,
because, temperature affects volume of solution,
not the weight of a solvent
May be imprecise / inaccurate Very precise and accurate

18. Classification of Solutions

19.  Based on size of solutes (Also
known as dissolved particles /
dispersed phase):
 Crystalloidal solution
 Colloidal solution
 Suspension
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 Based on whether the concentration is exactly known or not:
Standard solutions : Percent solution, normal, molar, molal, osmolar,
osmolal solution
 Nonstandard solution: Saturated, unsaturated, supersaturated
solutions
 Based on tonicity with respect to
plasma:
 Isotonic solution
 Hypotonic solution
 Hypertonic solution

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22. Solubility is the ability of a substance (the
solute), to mix into a liquid (the solvent)
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24. Osmolarity vs.
Tonicity of solution

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Osmolarity Tonicity
It is the total number of osmole of osmotically active
solutes (both permeable and nonpermeable) per liter
solution
It is the number of osmole of nonpermeable
osmotically active solutes per liter solution
Creation of transmembrane osmotic gradient
between 2 solutions across a semipermeable
membrane is not the function of osmolarity
Creation of transmembrane osmotic gradient
between 2 solutions across a semipermeable
membrane is the function of tonicity
It is the physical property of solution It is the physiological property of a solution as
it determines osmosis will occur or not
Tonicity is otherwise regarded as effective osmolarity as it determines whether there will be
osmosis or not by creation of transmembrane osmotic gradient. Nonpermeable solutes ((NaCl,
glucose, mannitol) that determines tonicity are considered as “effective osmole” and
Permeable solutes (urea, alcohol etc) are “ineffective osmole”

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Isoosmotic solution Isotonic solution
Solutions having same osmolarity
(Total solute concentration, both permeable
and nonpermeable)
Solutions having same tonicity
(Nonpermeable solute concentration only)

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29. Effect of tonicity of a solution on cell volume (e.g. RBC)
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Clinical importance of
tonicity of solution
What happens?
Isotonic fluid
(0.9 % NaCl)
 Does not disturb ECF tonicity
 Maintain osmotic equilibrium between ECF & ICF
Hypotonic fluid
(0.45 % NaCl)
 Reduces ECF tonicity causes water entry into cells.
-Cellular overhydration
-Cerebral oedema
-Coma
Hypertonic fluid
(3.0 % NaCl)
 Increases ECF tonicity causes water loss from cells.
-Cellular dehydration
-Cerebral dehydration
-Coma

31. Colloids & Crystalloids

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Crystalloid / Amicrons:
 Substances with size <1 nm which can
pass through semipermeable membrane
 Can not be seen by ultramicroscope
 Dialyzable
 Forms homogeneous / true solution
with water
 Osmotically very active, exert high
crystalloid OP in water
 Determines water movement across cell
membrane
 Example: electrolytes, non electrolytes
(glucose, amino acid, minerals etc)
Colloids / Submicrons:
 Substances with molecular size / atomic size
1 – 100 nm which can not pass through
semipermeable membrane
 Can be seen by ultramicroscope
 Non dialyzable
 Forms heterogeneous colloidal solution
(called colloidal system) with water
 Osmotically less active, exert less COP in
water
 Determines water movement across capillary
membrane
 Example: starch, glycogen, protein etc

33. Microns:
 Solutes having size >100 nm
 They form unstable emulsion / suspension with
water.
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34. Dispersed phase & dispersion medium:
In colloidal system,
- solute is known as dispersed phase (internal phase / discontinuous phase of a colloid)
- solvent is dispersion medium (external phase / continuous phase of a colloid)
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36. Solid in liquid : Sols
 Liquid in solids: Gels
 Liquid in liquid: Emulsion
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Types of colloid:
A) Hydrophilic / Lyophilic Colloid:
 Practically all colloids of living
system
 Solvent loving
 Have affinity to water
 They are easily solvated / hydrated
where a shell of water molecule is
formed around them
 Example: Protein, Polysaccharides,
bile salt etc
B) Hydrophobic / Lyophobic Colloid:
 Solvent hating
 Have no affinity to water
 They are kept in solution by hydrophilic
colloid adsorbed around them
 Example: Unconjugated bilirubin etc

38. Properties of Colloids:
 Physical properties: Size, shape, color, permeability through semi
permeable membrane etc
 Kinetic property: Brownian movement
 Optical property: Tyndall phenomenon
 Electrical property: Electrical charge, Electrophoresis, Iso-electric pH
(Zwitterion)
 Others: Non-dialyzable , surface phenomenon
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Brownian movement:
 Continuous, rapid & haphazard
movement of colloid particles in
solution
 Seen under ultra microscope
 It happens due to uninterrupted
buffeting on colloid particle given by
solvent molecules

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Tyndall / optical Phenomenon:
 When a beam of light passes
through a colloidal solution &
observed at right angle, the tract
of light becomes visible as white
line
 Occurs due to dispersion of
light rays by colloid particles.

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Electrical phenomenon:
 Colloids carry electrical charge (+ /-)
 They have definite isoelectric pH at
which they behave as zwitter ion,
become least soluble & may precipitate
out
 They undergo electrophoresis.
Surface phenomenon:
 Colloid particles have larger surface
area per unit mass
 They show increased phenomenon of
adsorption & interfacial tension

42. Importance of colloids:
 Colloids determine the COP of plasma, which is needed to
hold water within vascular compartment
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If plasma colloids & COP rises:
Water enters the blood vessels from
extra vascular space to expand the
blood volume
If plasma colloids & COP decrease:
Water comes out of the blood vessels to
extra vascular space and causes oedema

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Suspension:
 Heterogeneous system of
solute and water
 Size of solute (dispersed
phase) : >100 nm
 Example: Antacid
suspension, RBC in plasma
etc
Emulsion:
 Liquid-liquid heterogeneous system
 Dispersion of a liquid droplet to another liquid
in which it is insoluble . Here, one liquid behaves
as dispersed phase (solute) , the other behaves as
dispersion medium (solvent)
 Size of solute (dispersed phase) : 100 - 1000 nm
 Example: Milk (fat in water), cod liver oil
 Emulsifier : Substances that stabilize an
emulsion. e.g. bile salts

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True solution Colloidal solution Suspension
Homogeneous Heterogeneous Heterogeneous
Solutes :
 Size: <1 nm (amicrons /
crystalloid)
 Exist as molecule / ion
 Never sediments out on
standing
Solutes:
 Size: 1-100 nm (submicrons /
colloids)
 Exist as aggregates of 100-1000
molecules
 Never sediments out on
standing
Solutes:
 Size: >100 nm (microns)
 Exist as aggregates of millions
molecules
 Sediments out on standing
Exert high OP Exert very low / negligible OP Exert no OP
Example: Normal saline Example: Albumin solution Example: Antacid syrup

45. Dialysis

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Points
A method of separation of colloids and crystalloids from their
mixture
What is dialysis?
Principle of dialysis Is based on the fact that, crystalloid substances in solution can pass
through semipermeable membrane while colloid particles can not
Semipermeable membranes
used in dialysis
 May be parchment membrane, cellulose nitrate, cellulose acetate,
cellophane membrane etc.
 These are called dialyzing membrane / dialyzer, usually in the
form of an elongated tube / bag
 Dialyzing membrane containing mixture of crystalloids & colloids
are kept suspended in a vessel containing dialysis fluid
Function of dialyzing membrane Acts as a sieve retaining the larger particles.

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Points
 It is prepared without the crystalloid substances which are to be
separated.
The crystalloid particles from the mixture will diffuse out to the
dialysis fluid through the dialyzer down their concentration gradient,
leaving colloid particles behind within the dialyzer
 It is changed either periodically / continuously during the process
Dialysis fluid
Types of dialysis Peritoneal dialysis & hemodialysis
Importance of dialysis  Use as an artificial kidney for treatment of renal failure
 Treatment of hyperkalemia

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52. Osmosis & Diffusion

54. Surface tension

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 It is the force acting along the surface
of a liquid by which surface molecules
are held together
 Surface molecules experience a net
inward force that creates tension at the
surface & resist penetration
 Surface tension allows the liquid
droplets to contract to the smallest
possible area with spherical
conformation

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It is measured in newton per meter or joule per square meter
 Application:
 Digestion of fat : Role of bile salt for emulsification of fat
 Surfactant and lung function

57. Adsorption

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 A surface phenomenon
 The adhesion of atoms, ions or molecules
from a gas, liquid or dissolved solid to
a surface.
 This process creates a film of
the adsorbate on the surface of
the adsorbent.

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Adsorbate : The substance which gets
adsorbed on any surface
Adsorbent : The substance on the surface
of which adsorption takes place

62. Viscosity

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 Viscosity is a measure of a
fluid's resistance to flow.
 It describes the internal friction
of a moving fluid.
 A fluid with large viscosity
resists motion because its
molecular makeup gives it a lot of
internal friction.
 A fluid with low viscosity flows
easily because its molecular
makeup results in very little
friction when it is in motion.

64. Isotopes

65. What is Isotope?
Atoms of same element with same atomic number but different atomic
weight
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