SURFACE TENSION, INTERFACIAL TENSION, SURFACE FREE ENERGY, Measurement of surface and interfacial tension-capillary rise method, drop number method, drop weight method, Du Nuoy tensiometer method, Spreading of liquids, spreading coefficient, surface active agents, hydrophilic-lipophilic balance, soluble monolayers, Adsorption on solid surface, Isotherms
In this presentation:
Surface Tension
Interfacial Tension
Definition of inerfacial tension in different ways
Measurement of interfacial and surface tesion
Solubility of drugs: Solubility expressions, mechanisms of solute solvent interactions, ideal solubility parameters, solvation & association, quantitative approach to the factors
influencing solubility of drugs, diffusion principles in biological systems. Solubility
of gas in liquids, solubility of liquids in liquids, (Binary solutions, ideal solutions)
Raoult’s law, real solutions. Partially miscible liquids, Critical solution temperature . Distribution law, its limitations and applications
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
INCLUDES SPREADING COEFFICIENT AND ITS THEORY AND ALSO FEW OF ITS APPLICATION IN PHARMACEUTICAL FIELD
WILL BE HELPFUL FOR B PHARMACY STUDENTS
INCLUDES HOW IT IS DERIVED AND ALSO HOW IT IS RELATED TO SPREADING OF A CREAM OR OINTMENT ON OUR SKIN
IMPORTANCE OF SPREADING COEFFICIENT
In this presentation:
Surface Tension
Interfacial Tension
Definition of inerfacial tension in different ways
Measurement of interfacial and surface tesion
Solubility of drugs: Solubility expressions, mechanisms of solute solvent interactions, ideal solubility parameters, solvation & association, quantitative approach to the factors
influencing solubility of drugs, diffusion principles in biological systems. Solubility
of gas in liquids, solubility of liquids in liquids, (Binary solutions, ideal solutions)
Raoult’s law, real solutions. Partially miscible liquids, Critical solution temperature . Distribution law, its limitations and applications
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
INCLUDES SPREADING COEFFICIENT AND ITS THEORY AND ALSO FEW OF ITS APPLICATION IN PHARMACEUTICAL FIELD
WILL BE HELPFUL FOR B PHARMACY STUDENTS
INCLUDES HOW IT IS DERIVED AND ALSO HOW IT IS RELATED TO SPREADING OF A CREAM OR OINTMENT ON OUR SKIN
IMPORTANCE OF SPREADING COEFFICIENT
When phases exist together, the boundary between two of them is known as interface.
When the phase is in contact with atmosphere it is termed as surface.
Surface and Interfacial tension [Part-3(a)](Measurement of Surface and Inter...Ms. Pooja Bhandare
MEASUREMENT OF SURFACE AND INTERFACIAL TENSION
Capillary Rise Method, Drop Count and Weight Method.
Wilhelmy Plate Methods ,The DuNouy Ring Method.
Capillary Rise Method: Upward force due to surface tension: Drop count and Weight method Downward Force: Drop weight method: Drop count method
IT INCLUDES HOW A SURFACTANT MOLECULE BEING DISTRIBUTED AT A LIQUID SURFACE/INTERFACE
ALSO EXPLAINS THE STRUCTURE OF A SURFACTANT MOLECULE AND HOW IT WILL B ORIENTED IN BOTH POLAR AND NON POLAR LIQUIDS
EXPLAIN CRITICAL MICELLAR CONCENTRATION AND ITS IMPORTANCE
MICELLE FORMATION AND STRUCTURE OF MICELLE
Solubility of Drugs (PHYSICAL PHARMACEUTICS-I)Rakesh Mishra
Solubility expressions, mechanisms of solute solvent interactions,solubility parameters, factors influencing
solubility of drugs, diffusion principles in biological systems, Raoult’s law, real solutions. Partially miscible
liquids(Phase equilibria, Phase rule, One , two and three component systems, ternary phase
diagram, Critical solution temperature and applications). Distribution law, its limitations and
applications
When phases exist together, the boundary between two of them is known as interface.
When the phase is in contact with atmosphere it is termed as surface.
Surface and Interfacial tension [Part-3(a)](Measurement of Surface and Inter...Ms. Pooja Bhandare
MEASUREMENT OF SURFACE AND INTERFACIAL TENSION
Capillary Rise Method, Drop Count and Weight Method.
Wilhelmy Plate Methods ,The DuNouy Ring Method.
Capillary Rise Method: Upward force due to surface tension: Drop count and Weight method Downward Force: Drop weight method: Drop count method
IT INCLUDES HOW A SURFACTANT MOLECULE BEING DISTRIBUTED AT A LIQUID SURFACE/INTERFACE
ALSO EXPLAINS THE STRUCTURE OF A SURFACTANT MOLECULE AND HOW IT WILL B ORIENTED IN BOTH POLAR AND NON POLAR LIQUIDS
EXPLAIN CRITICAL MICELLAR CONCENTRATION AND ITS IMPORTANCE
MICELLE FORMATION AND STRUCTURE OF MICELLE
Solubility of Drugs (PHYSICAL PHARMACEUTICS-I)Rakesh Mishra
Solubility expressions, mechanisms of solute solvent interactions,solubility parameters, factors influencing
solubility of drugs, diffusion principles in biological systems, Raoult’s law, real solutions. Partially miscible
liquids(Phase equilibria, Phase rule, One , two and three component systems, ternary phase
diagram, Critical solution temperature and applications). Distribution law, its limitations and
applications
Introduction
Definition
Features desired in pharmaceutical suspension
Advantage/Disadvantages of pharmaceutical suspension
Flocculated and deflocculated suspension
Interfacial properties of suspending particles
Settling in suspensions
Effect of Brownian movement,
Sedimentation of flocculated particles,
Sedimentation parameters
Formulation of suspensions
Wetting of Particles,
Controlled flocculation,
Flocculation in structured vehicle
surface & interfacial tension, surface free energy, Gibb’s equation, thermodynamic & kinetic stability of disperse systems
Definition, advantages and disadvantages, desirable features and pharmaceutical dispersions
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
1. Interfacial phenomena
SURFACE TENSION, INTERFACIAL TENSION, SURFACE FREE ENERGY
Measurement of surface and interfacial tension-capillary rise method, drop number method, drop weight
method, Du Nuoy tensiometer method
Spreading of liquids, spreading coefficient, surface active agents, hydrophilic-lipophilic balance, soluble
monolayers
Adsorption on solid surface, Isotherms
3. Liquid Interfaces
3
• Interface is the boundary between two phases.
• Surface is a term used to describe either a gas-solid or a
gas- liquid interface.
• Interfacial phase is a term used to describe molecules
forming the interface between two phases which have
different properties from molecules in the bulk of each
phase.
4. Surface Tension
• Molecules in the bulk liquid are surrounded in all
directions by other molecules for which they have an
equal attraction (only cohesive forces).
• Molecules at the surface can only
develop cohesive forces with
other molecules that are below
and adjacent to them; and can
develop adhesive forces with
molecules of the other phase.
4
5. Surface Tension
This imbalance in the molecular attraction
will lead to an inward force toward the
bulk that pulls the molecules of the
interface together and contracts the
surface, resulting in a surface tension.
Definition: Surface tension is the force per
unit length that must be applied parallel to
the surface to counterbalance the net
inward pull. It has the units of dynes/cm or
N/m.
5
6. Interfacial Tension
• Interfacial tension is the force per unit length existing at the
interface between two immiscible phases (units are dynes/cm or
N/m).
• The term interfacial tension is used for the force between:
6
Two liquids = γLL Solid liquids = γSL
7. Interfacial Tension
• The term surface tension is reserved for the tensions:
Liquid-vapor = γ
Solid-vapor = γ
• Interfacial tensions are weaker than surface tensions because
the adhesive forces between two liquid phases forming an
interface are greater than that between liquid and gas phase
7
8. Surface Free Energy
8
The surface layer of a liquid possesses additional energy as compared to the
bulk liquid.
If the surface of the liquid increases (e.g. when water is broken into a fine spray), the
energy of the liquid also increases.
Because this energy is proportional to the size of the free surface, it is called
a surface free energy:
𝑾= 𝜸 ∆ 𝑨
𝑾 Surfacefree energy (ergs)
𝜸 surface tension (dynes/cm)
∆ 𝑨 increase in area (cm2).
Therefore, surface tension can also be defined as the surface free energy per unit area of
liquid surface.
9. Surface Free Energy
Each molecule of the liquid has a tendency to move inside the liquid from
the surface; therefore, when the surface is increased, the liquid takes the
form with minimal surface and as a result, minimal surface energy:
9
Sphere shape
10. Measurement of Surface Tensions
𝜸 surface tension
𝒓 radius of capillary
𝒉 height
𝒑 density of the liquid
𝒈 acceleration of gravity
This method cannot be used to obtain interfacial tensions.
Capillary Rise Method
When a capillarytube is placed in a liquidcontained in a
beaker, the liquid rises up in the tube to a certain distance.
By measuring this rise in the capillary, it is possible to
using thedetermine the surface tension of the liquid
formula:
𝜸 = ½ 𝒓 𝒉 𝒑 𝒈
10
11. Measurement of Surface Tensions
The DuNoüy Ring Method
The force necessary to detach a
platinum–iridium ring immersed at the
surface or interface is proportional to the
surface or interfacial tension. The
surface tension is given by the formula:
The DuNoüy tensiometer is widely
used for measuring surface and
interfacial tensions.
13. Spreading of liquid
• When Oleic acid dropped on water, it immediately spreads on
the surface of water
• Oleic Acid – Spreading Liquid (L)
• Water – Sub-layer Liquid (S)
• Generally spreading occurs when adhesive force is more
than cohesive force
14. Spreading Coefficient • Work of Cohesion (Wc) may be
defined as the surface free energy
increased by separating a column of
pure liquid into two halves
• Surface free energy increase = γ dA
• Wc = γL (dA+dA) = 2 γLdA
• Here the column is of cross sectional
area is 1cm2 (dA= 1cm2)
• Wc = 2 γL
15. • Work of Adhesion (Wa) may be defined
as the surface free energy increased by
separating a column of two immiscible
liquids at its boundary into two sections
• As two sections of immiscible liquids
are already separated by a boundary, the
energy requirement will be less by an
amount γLS dA
• Wa = γLdA + γS dA - γLS dA
• Here the columns are of cross sectional
area 1cm2
• Wa = γL + γS - γLS
Spreading Coefficient
16. Spreading coefficient
• Spreading coefficient (S) is the difference between work of adhesion
and work of cohesion
S = Wa –Wc
= (γL + γS – γLS) - 2γL
= γS – γL – γLS
• S = γS – (γL + γLS)
• γL - Surface tension of spreading liquid
• γS - Surface tension of sublayer liquid
• γLS - Interfacial tension
17. Spreading coefficient
• Spreading occurs when spreading
coefficient S is positive i.e., γS > (γL+ γLS).
When free energy of the spreading liquid
and the interfacial tension with the sub layer
is less than that of sublayer the spreading
becomes spontaneous to reduce free energy
of sublayer.
• If spreading coefficient S is negative ie,
(γL+ γLS) > γS Spreading liquid forms
globules or floating lens means spreading
will not take place
18. Spreading
• There may be saturation of the liquid with the other and there may be
change in the surface tension of the sublayer liquid
• In that case the spreading coefficient may become negative after
saturation, the spreading liquid coalesces and form a lens on the
surface of the sublayer
• In the case of a DUPLEX FILM if S become negative after saturation,
it forms a monolayer and excess liquid remains as lens on the surface
19. Spreading
• Fatty acids and alcohols have high spreading coefficient
• As non-polar chain length increases in an acid or alcohol spreading
coefficient decreases
• Propionic acid and ethyl alcohol having high spreading coefficient
20. Applications of spreading coefficients
• Absorption of medicament from creams, lotions, etc. on skin
• Stabilization of emulsions
22. Surface Active Agents
• Molecules and ions that are adsorbed at interfaces are termed
surface-active agents or surfactants.
• Surfactants have two distinct functional groups in their chemical
structure, one of which is water-liking (hydrophilic) and the other of
which is lipid-liking (lipophilic).
• These molecules are referred to as amphiphile.
22
23. Surface Active Agents
When such molecule is placed in an air-water or oil-water system,
the polar groups are oriented toward the water, and the nonpolar
groups are oriented toward the air or oil.
24. Reduction of Surface Tension
Principle: When surfactants are dissolved in water they can reduce surface tension by
replacing some of the water molecules in the surface so that the forces of attraction
between surfactant and water molecules are less than those between water molecules
themselves, hence the contraction force is reduced.
24
25. Classification of surface active agents
• Non-ionic surfactants
Have low toxicity and high stability and compatibility,
e.g. Sorbitan esters (spans) and Polysorbates (tweens).
• Anionic surfactants
Have bacteriostatic action
e.g. Sodium Lauryl Sulphate
• Cationic surfactants
Have bactericidal activity
e.g. benzalkonium chloride
• Ampholytic Surfactants
• Phospholipids
25
26. Reduction of Surface Tension
Effect of Structure on Surface Activity
• The surface activity (surface tension reduction) of a particular surfactant depends
on the balance between its hydrophilic and hydrophobic properties.
• An increase in the length of the hydrocarbon chain (hydrophobic) of a surfactant
increases the surface activity.
• An increase in the length of the ethylene oxide chain (hydrophilic) of a non-ionic
surfactant results in a decrease of surface activity.
26
28. HLB System
• Definition: The hydrophile-lipophile balance
(HLB) system is an arbitrary scale for
expressing the hydrophilic and lipophilic
characteristics of an emulsifying agent.
• Agents with HLB value of 1-8 are lipophilic and
suitable for preparation of w/o emulsion,
• Those with HLB value of 8-18 are hydrophilic
and good for o/w emulsion.
29. HLB System
The oil phase of an o/w emulsion requires a specific HLB, called the required hydrophile–
lipophile balance (RHLB).
% emulsifier with high HLB = RHLB- HLB Low
HLB High - RHLB
31. Monolayers
• Types of monolayers on basis
of solubility of adsorbate
(amphiphile/surfactant)
• Soluble monolayers
• Insoluble monolayers
Soluble monolayer
Insoluble monolayer
32. Soluble monolayers
Surface excess concentration ( 𝜞 ) amount
(concentration) of amphiphile per unit
area in excess of that in bulk of liquid, c
It is the difference between the amount per
unit area of a solute in the surface of a
real system and that of a hypothetical
system (without adsorption).
c, concentration of amphiphile is zero in
case of insoluble monolayers
𝜞= surface excess (g/cm2)
𝑹= gas constant (8.314 J mol–1 K–1)
T= absolute temperature (kelvins)
c= amphiphile concentration in bulk (mol m–3)
𝑑γ/dc is change in ST with chance in bulk conc.
𝜞 =
𝑐
𝑅𝑇
𝑑γ
𝑑𝑐
Surface excess is expressed by
the Gibbs adsorption equation:
33. Reduction of Surface Tension
𝑨 =
Surface Area
• The surface area (𝑨)is the area
occupied by one surfactant
molecule at the solution surface.
It can be calculated using the equation:
N = Avogadro number (6.023 × 1023 molecules /mol)
N 𝜞
𝟏
𝜞 = surface excess
34. Micellisation
• Micelles are formed when the
concentration of a surfactant reaches a
given concentration called critical
micelle concentration (CMC) in which
the surface is saturated with surfactant
molecules.
• The main reason for micelle formation is
to obtain a minimum free energy state.
• In a micelle, polar or ionic heads form an
outer shell in contact with water, while
non polar tails are sequestered in the
interior to avoid water.
Concentration
SurfaceTension
35. Micellisation
Solubilization
• Solubilization is the process where water-insoluble substances are brought
into solution by incorporation into micelle.
• Solubilization does not occur until the milcells are formed (i.e. above
CMC)
• The amount of substance solubilized increases as the number of micelles
increases.
37. Adsorption of solute from liquid to solid surface
Types of Adsorption
Adsorption is the adhesion of atoms,
ions, or molecules from a gas, liquid,
or dissolved solid to a interface.
There are two general types of
adsorption:
1. Physical adsorption, in which the
adsorbate is bound to the surface
through the weak van der Waals
forces.
2. Chemical adsorption or
chemisorption, which involves the
stronger valence forces.
38. Adsorption of Gas
• Adsorption & Desorption (evaporation)
• Physical adsorption, in which the
adsorbate is bound to the surface
through the weak van der Waals forces.
• Chemical adsorption or chemisorption,
which involves the stronger valence
forces.
• Adsorbate: material which get adsorb
(Gas/solute) (x moles)
• Adsorbent: material on which
adsorption takes place (m grams)
m
x
40. Langmuir adsorption isotherm
• Molecules of gas adsorb on active sites on adsorbent
• Fraction of active sites occupied (at pressure p) are ϴ
• Fraction of un-occupied sites are 1- ϴ
• Rate of adsorption is proportional to pressure and no. of un occupied
sites
• r1=k1(1-ϴ)p
• Rate of desorption (evaporation is proportional to no. of occupied sites
• r2=k2ϴ
• At equilibrium r2=r1
41. Langmuir adsorption isotherm
• ϴ =
k1
p
k2
+k1
p
• ϴ =
(k1
/k2
)p
1+(
k1
k2
)p
• y =
ym
bp
1+bp
•
p
y
=
1
bym
+
p
ym
If we replace
• (k1/k2) with b
• ϴ with y/ym
Where,
• y= mass of gas adsorb per gram of adsorbent at pressure p
• ym= mass of gas adsorb on adsorbent on 1 gram of adsorbent
when monolayer is formed
The plot of p/y against p gives straight line and ym and b can be
obtained by slop and intercept
• k2ϴ = k1(1-ϴ)p
43. Other types of adsorption
isotherm
Type I : Previous
Type II : Sigmoidal when gas undergo
physical adsorption on non-porous solid to
form monolayer. Described by BET
equation. Multilayer formation and
condensation within pores.
Type IV : Adsorption on porous solid.
Capillary condensation
Type III & Type V : Heat of adsorption of
gas in first layer is less than latent heat of
condensation in successive layers. Capillary
condensation occur in type V
Surface area can be determined where
monolayer formation is detected … Type I,
II & IV
45. Wetting
• Force of attraction between solid and liquid play important role
• Angle of contact range (0° to 180 °)
46. Wetting phenomenon
• Contact angle is the angle between liquid droplet and surface over which it spreads.
• Important action of wetting is to reduce angle of contact
• Draves test for to test wetting property of wetting agent… time required to sink
weighted cotton yarn of standard solution.
47. Young’s equation
• γs= γSL - γL cos ϴ
• Where ϴ= angle of contact
• We know that spreading coefficient ‘S’
• S= γS – γL – γLS
• Combining both these equations, substituting value of γs in second
equation
• S = γL (cos ϴ -1)
• Surface tension when, cos ϴ =1 is known as critical surface tension