This document discusses conductometric titration, which is an electrochemical analytical method that measures the electrical conductance of an electrolyte solution. It describes the principles and instrumentation of conductometry, including how conductivity is measured using a conductivity meter or by performing a titration. Some key applications of conductometric titration are determining the end point of acid-base and precipitation titrations, and it has various uses in fields like environmental analysis, food testing, and quality control.
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
Semisolid dosage forms: Definitions, classification, mechanisms and factors influencing dermal penetration of drugs. Preparation of ointments, pastes, creams and gels. Excipients used in semi solid dosage forms. Evaluation of semi solid dosages forms
Neutralization curves in acid base analytical titrations, indicators.nehla313
Neutralization curves in acid base analytical titrations, indicators,
strong acid strong base
weak acid strong bse
strong acid weak base
weak acid and weak base
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
EDTA Titration
The earliest voltammetric technique
Heyrovsky invented the original polarographic method in 1922, conventional direct current polarography (DCP).
It employs a dropping mercury electrode (DME) to continuously renew the electrode surface.
Diffusion is the mechanism of mass transport.
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
Capillary tube about 10-15cm
Int. diameter of 0.05mm
A vertical distance being maintained betwwen DME and the solution
Drop time of 1-5 seconds
Drop diameter 0.5mm
The supporting electrolyte
is a solution of (KNO3, NaCl, Na3PO4) in which the sample (which must be electroactive) is dissolved.
Function of the supporting electrolyte
It raises the conductivity of the solution.
It carries the bulk of the current so prevent the
migration of electroactive materials to working
electrode.
It may control pH
It may associate with the electroactive solute as
in the complexing of the metal ions by ligands.
Semisolid dosage forms: Definitions, classification, mechanisms and factors influencing dermal penetration of drugs. Preparation of ointments, pastes, creams and gels. Excipients used in semi solid dosage forms. Evaluation of semi solid dosages forms
Neutralization curves in acid base analytical titrations, indicators.nehla313
Neutralization curves in acid base analytical titrations, indicators,
strong acid strong base
weak acid strong bse
strong acid weak base
weak acid and weak base
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
EDTA Titration
The earliest voltammetric technique
Heyrovsky invented the original polarographic method in 1922, conventional direct current polarography (DCP).
It employs a dropping mercury electrode (DME) to continuously renew the electrode surface.
Diffusion is the mechanism of mass transport.
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
Capillary tube about 10-15cm
Int. diameter of 0.05mm
A vertical distance being maintained betwwen DME and the solution
Drop time of 1-5 seconds
Drop diameter 0.5mm
The supporting electrolyte
is a solution of (KNO3, NaCl, Na3PO4) in which the sample (which must be electroactive) is dissolved.
Function of the supporting electrolyte
It raises the conductivity of the solution.
It carries the bulk of the current so prevent the
migration of electroactive materials to working
electrode.
It may control pH
It may associate with the electroactive solute as
in the complexing of the metal ions by ligands.
Conductometry / conductometric titrationRabia Aziz
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
conductometric titration
Introduction
Ohm’s law.
Conductometric measurements.
Factor affecting conductivity.
Application of conductometry.
2.Conductometric titration-:
Introduction.
Types of conductometric tiration.
Advantages of conductometric tiration.
3.Recent devlopement
Conductometry:
is the simplest of the electroanalytical techniques; by Kolthoff in 1929.
Conductors are:
either metallic (flow of electrons) or electrolytic (movemenmt of ions).
Conductance of electricity:
migration of positively charged ions towards the cathode and negatively charged ones towards the anode
(i.e.) current is carried by all ions present in solution.
Conductance depends on the number of ions in solun.
Factors affecting conductance:
1- Temperature:
(1C increase in temperature causes 2 % increase in conductance).
2- Nature of ions
Size, molecular weight and number of charges.
3- Concentration of ions:
As the number of ions increases, the conductance increases.
4- Size of electrodes
Conductance is directly proportional to the cross sectional area (A).
Conductometry is used to analyze ionic species and to monitor a chemical reaction by studying the electrolytic conductivity of the reacting species or the resultant products.
Conductometry is an electrochemical method of analysis involve the measurement of the electrical conductivity of a solution. The conductance is defined as the current flow through the conductor.
In other words, it is defined as the reciprocal of the resistance.
Potentiometry: Electrical potential, electrochemical cell, reference electrodes, indicator
electrodes, measurement of potential and Ph, construction and working of electrodes,
Potentiometric titrations, methods of detecting end point, Karl Fischer titration.
Spectroscopy for Pharmaceutical Analysis and Instrumental Method of Analysis....Yunesalsayadi
Spectroscopy for Pharmaceutical Analysis and Instrumental Method of Analysis.
Atomic spectroscopy, Molecular Spectroscopy, Beer Lambert's Law, Fundamental Laws of Photometry, application of beer lambert law in equilibrium constant, Chromophore, Auxochrome, Bathochromic shift, Hypsochromic shift, Hypochromic and Hyperchromic effects, Effect of solvent on absorption spectra
GLP is an FDA regulation.
It is defined in OECD principles as ―a quality system concerned with organizational process and the conditions under which non-clinical health and environmental safety studies are planned, performed, monitored, recorded, archived and reported.
GLP extends to include food and color additives, animal food additives, human and animal drugs, medical devices for human use, biological products, and electronic products.
GLP is a formal regulation that was created by the USFDA in 1978 having worldwide impact.
Non-US companies that wanted to do business with the United states or register their pharmacies in the United States had to comply with the United States GLP regulations.
In 1981 an organization named OECD (organization for economic co-operation and development ) produced GLP principles that are international standard.
Quality and Integrity of the Safety Data
In the early 70’s FDA became aware of cases of ( PLP ) poor laboratory practice all over the United States.
FDA decided to do an in-depth investigation in 40 toxicology labs. They discovered a lot fraudulent activities and a lot of poor lab practices.
Examples of some of these ( PLP )poor lab practices found were: Equipment not been calibrated to standard form , therefore giving wrong measurements. Incorrect/inaccurate accounts of the actual lab study.
Validation.
Validation is establishing documented evidence which provides a high degree of assurances that a specific process or equipment will consistently produce a product or result meeting its predetermined specifications and quality attributes”.
A system must be qualified to operate in a validated process
The results of analytical procedures should be:
— reliable
— accurate
— reproducible
The characteristics that should be considered during validation of analytical methods are:
— specificity
— linearity
— range
— accuracy
— precision
— detection limit
— quantitation limit
— robustness
PST-392 Sources of quality variations and their control (1).pptxYunesalsayadi
The difference in characteristics between two items known as variation. This variation may be due to substandard quality of raw material, carelessness on the part of operator, fault in machinery system etc. Variation in quality is of types:
1.Variation by chance
2. Assignable cause
PST-392 Introduction to Quality Assurance (1).pptxYunesalsayadi
Introduction to Quality assurance.
According to U.S.F.D.A
“Quality should be built into the product, and testing alone cannot be relied on to ensure product quality”.
Building Quality into the product involves having controls at every stage of manufacturing and not only terminal controls.
These include controls on all input resources like:
people,
facilities,
equipment,
materials,
process
and testing etc.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
(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.
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 .
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Richard's aventures in two entangled wonderlandsRichard 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.
1. DISCOVER . LEARN .
EMPOWER
Mr. Yunes Alsayadi
Assistant Professor
of Pharmaceutical
Analysis
E 10695
UNIVERSITY INSTITUTE OF
PHARMA SCIENCES
B. Pharm
Conductometry
3. Introduction
Conductometry is used to analyze ionic species and to
monitor a chemical reaction by studying the
electrolytic conductivity of the reacting species or the
resultant products.
It has notable applications in analytical chemistry.
Conductivity measurement can be performed directly
by using a conductivity meter or by performing
conductometric titration.
Conductometric analysis of electrolytes is a long-
time practice.
4. Definition
It is an electrochemical method of analysis used for the
determination or measurement of the electrical
conductance of an electrolyte solution by means of a
conductometer.
Electric conductivity of an electrolyte solution depends
on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
5. Principle
The main principle involved in this method is that the
movement of the ions creates the electrical
conductivity. The movement of the ions is mainly
depended on the concentration of the ions.
The electric conductance in accordance with ohms
law which states that the strength of current (i)
passing through conductor is directly proportional to
potential difference & inversely to resistance.
i =V/R
6. Important Definitions and Relations
Conductance (G): ease with which current flows per unit area of
conductor per unit potential applied & is reciprocal to resistance (R)
, its unit is Siemens (ohm-1)
G = 1⁄ R
Resistance (R): is a measure of the conductors opposition to the flow
of electric charge, its unit is ohm.
R =1/G
Specific resistance (ρ): resistance offered by a substance of 1 cm
length (l) and 1 sq.cm surface area (A), its unit is ohm cm
ρ = aR/l
Specific conductivity (kv): conductivity offered by a substance of 1
cm length (l) and 1 sq. cm surface area, its unit is siemens cm-1
kv =1 ⁄ ρ
7. Equivalent conductivity (λv): conductivity of a solution
containing equivalent weight of the solute between
electrodes 1 cm apart and 1 sq. cm surface area, its unit is
siemens cm-1
Equivalent conductivity = specific conductivity (kv) X volume
of solution containing 1 gram equivalent weight of electrolyte
Molar conductivity (µv): conductivity of a solution
containing molecular weight of the solute between
electrodes 1 cm apart and 1 sq. cm surface area
Molar conductivity = specific conductivity (kv) X
volume of solution containing 1 molecular weight of
electrolyte
8. The conductance of the solution
depends on:
Temperature: It is increased by increase of
temperature.
Nature of ions: size, molecular weight, number
of charges the ion carries and other factors
The concentration of ions: As the number of
ions increases the conductance of the solution
increases.
The size of the electrodes.
9. Instrumentation
The instrument used for measurement of conductance are known as
conductometers. It consists of :
Current source
Mechanical high frequency AC generator.
DC current is not employed in conductance measurement because
electrodes becomes polarised leading to high cell resistance.
Conductivity cells
Made of pyrex or quartz and are fitted with two platinum electrodes.
Should be placed in vessel containing water to maintain constant
temperature
Types :
1. Wide mouthed cell
2. Cell for reactions producing precipitation
3. Dip type cells Instrumentation
10. Electrodes:
Platinum sheets, each of 1 cm2 are fixed at
distance of 1 cm
The surface is coated with platinum
to avoid polarization effects and
increase effective surface area.
Platinisation of electrodes is done by coating solution of 3%
chlorplatinic acid and lead acetate on it to get uniform coating.
Electrodes usage depends on conductivity and concentration.
If concentration is low then electrodes should be largely and
closely packed.
11. Measurment
The instrument used to measure conductance is
called conductance bridge or conductometer.
Classical circuit employed for measurement is
wheatstone bridge.
Various types are:
– Kohlrausch conductance bridge
– Direct reading conductance bridge
– Phillips conductance bridge
– Mullard’s conductance bridge
– Pye’s conductance bridge Measurement
12. The measured conductivity is not always equal to the
specific conductivity of solution, because the physical
configuration of platinum electrode i.e, length and
area of electrodes varies from one another
Hence conductivity of solution is obtained by
calculating a factor called “cell constant”.
Cell constant: Defined as ratio of distance between
the two electrodes(l) to the area of electrodes(A)
Therefore, θ =1 ⁄ A
13. Conductometric Titrations
Principle
The determination of end point of a titration by
means of conductivity measurements is known as
conductometric titration.
During the course of titration, the conductivity of the
solution changes, since there is change in the number
and the mobility of ions.
At the end point of the titration, there is a sharp
change in the conductivity of a solution shown by the
intersection of the lines in the graph of conductivity
Vs volume of titrant added.
14. Types of conductometric titrations
Acid –base or neutral titrations
Strong Acid with a Strong Base, e.g. HCl with NaOH
When the base is added in HCl solution,
the conductance falls due to the
replacement of hydrogen ions by the
added cation as H+ ions react with OH −
ions to form undissociated water.
After the equivalence point, the
conductance increases due to the large
conductivity of OH- ions
15. Weak Acid with a Strong Base, e.g. acetic acid with NaOH
Initially the conductance is low due to
the feeble ionization of acetic acid,
followed by increase due to NaOH
Beyond the equivalence point,
steep rise due to excess of NaOH.
16. Strong Acid with a Weak Base, e.g. sulphuric acid with dilute ammonia
Initially the conductance is high and then
it decreases due to the replacement of H+.
But after the endpoint has been reached
the graph becomes almost horizontal,
since the excess aqueous ammonia is not
appreciably ionised in the presence of
ammonium sulphate
17. Weak Acid with a Weak Base, e.g. sulphuric acid with dilute ammonia
The nature of curve before
the equivalence point is similar to the curve
obtained by titrating weak acid against strong base.
After the equivalence point, conductance
virtually remains same as the weak base
which is being added is feebly ionized
and, therefore, is not much conducting
18. Precipitation Titrations
eg Potassium chloride Vs Silver nitrate
KCl + AgNO3 AgCl + KNO3
When silver nitrate added, the first part of the curve
shows no increase in conductivity as there is only
replacement of chloride ions with nitrate ions.
After end point conductivity increases because of
increase in the concentration of silver as well as
nitrate ions.
19. Application
Check water pollution in rivers and lakes.
Solubility of sparingly soluble salts like AgCl, BaSO4 can be
detected
Determination of atmosphericSO2,etimation of vanillin in vanilla
flavour Applications
Alkalinity of fresh water.
Salinity of sea water (oceanography)
Used to trace antibiotics.
Deuterium ion concentration in water- deuterium mixture Food
microbiology- for tracing micro organisms
Tracing antibiotics
Estimate ash content in sugar juices
Purity of distilled and de -ionised water can determined
20. Advantages
Determination of specific conductivity is not
required.
No indicator is necessary.
Suitable for coloured or dilute solutions.
Since end point is determined by graphical
means accurate results are obtained with
minimum error.
Used for analysis of turbid suspensions, weak
acids, weak bases, mix of weak & strong acids.
21. Disadvantages
Increased level of salts in solution masks the
conductivity changes , in such cases it does not
give accurate results.
Application of conductometric titrations to
redox systems is limited because, high
concentrations of hydronium ions in the
solution tends to mask the changes in
conductance