Volume 10 - Materials Characterization Part 5 docx

Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England... Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England Polarographic circuit... Crow, Departmen

Table 14 Commonly used volumetric procedures

Permanganate titration for chromium and vanadium

Thomas R Dulski, Carpenter Technology Corporation

Thomas R Dulski, Carpenter Technology Corporation

Thomas R Dulski, Carpenter Technology Corporation

Thomas R Dulski, Carpenter Technology Corporation

Mark A Arnold, Department of Chemistry, University of Iowa

Mark A Arnold, Department of Chemistry, University of Iowa

Mark A Arnold, Department of Chemistry, University of Iowa

Types of ion-selective membrane electrodes (a) Glass membrane electrode (b) Polymer membrane electrode (c) Solid crystalline (pressed pellet or single crystal) membrane electrode

Table 1 Selectivity constants for some commercially available electrodes

Mark A Arnold, Department of Chemistry, University of Iowa

∆

Mark A Arnold, Department of Chemistry, University of Iowa

Configuration of an ammonia gas-sensing membrane electrode

Mark A Arnold, Department of Chemistry, University of Iowa

Schematic of reference electrodes (a) Single junction (b) Double junction

General experimental arrangement for potentiometric membrane electrodes

Mark A Arnold, Department of Chemistry, University of Iowa

Mark A Arnold, Department of Chemistry, University of Iowa

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

Polarographic circuit G, microammeter

Direct-current polarograms of 10-4 mol/L Cd2+, Zn2+, and Mn2+ in 0.1 mol/L KNO3 as supporting electrolyte The baseline curve is that obtained with supporting electrolyte alone

Polarograms for equal concentrations of two species whose reduction involves the same number of electrons A, reversible; B, irreversible

The shape of a polarogram distorted by a maximum

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

Single-sweep voltammogram obtained at a carbon-wax electrode for 10-3 mol/L Ag+ ion in 0.1 mol/L KNO3 as supporting electrolyte The reversal of the potential scan direction after the cathodic signal is fully developed produces an anodic signal whose size is enhanced relative to the first, because its origin is in material deposited and accumulated in the forward sweep The principle, used for longer cathodic deposition times at constant potential, is the basis for stripping analysis

Fundamentals of cyclic voltammetry (a) Symmetrical saw-tooth potential-time variation used in cyclic voltammetry (b) Corresponding cyclic voltammogram expected for a near-reversible system The greater the separation between the peaks for forward and reverse scans, the more irreversible the electrode reactions Letters a through g show the stages of the cyclic variation and the corresponding positions adopted by the resultant signal

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

Relative rates of decay of Faradaic (if) and capacitance (ic) currents after imposition of voltage change in the potential square-wave profile

In normal pulse polarography,

Relationship between drop time, pulse duration, and current measurement period used in normal pulse polarography

Differential pulse polarography

Relationship between drop time, pulse duration, and current signal in differential pulse polarography

Polarograms of 10-5 mol/L Cd2+, Zn2+ and Mn2+ A, normal pulse mode; B, differential pulse mode Supporting electrolyte 0.1 mol/L KNO3 Curves A and B indicate the presence of some impurity showing a signal

at approximately -0.85 V This may originate in the supporting electrolyte and emphasizes the importance of extreme purity of such salts required in analysis at these levels In this case, the interference does not prevent

the measurement of the peak heights in curve B

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

∆

∆

β

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

Direct-current and differential pulse polarograms of nickel in general-purpose cobalt nitrate A, sample solution; B, after addition of 2 mL of 0.01 mol/L standard; C, after addition of 4 mL of standard; D, after addition of 6 mL of standard All traces begin at -0.5 V versus SCE

Direct-current and differential pulse polarograms of nickel in analytical-grade cobalt nitrate A, sample solution; B, after addition of 0.1 mL of 0.01 mol/L standard; C, after addition of 0.2 mL of standard All traces begin at -0.5 V versus SCE

∆

Differential pulse polarogram obtained in analysis of effluents A, standard solution; 10 mL supporting electrolyte + I mL solution containing 10 mg/L copper, lead, cadmium, nickel, and zinc (copper/lead appear under the same peak in the medium used); B, effluent sample I; C, effluent sample I + standard solution A presence of copper/lead, nickel, and zinc indicated; D, effluent sample II; E, effluent sample II + standard solution A presence of cadmium and possibly small amounts of copper/lead and zinc indicated

D.R Crow, Department of Chemistry, The Polytechnic, Wolverhampton, England

D.R Browning, Consultant

General Uses

•

ω ω

D.R Browning, Consultant

The ability of metals to adhere to the cathode

The rate of flow of ions

D.R Browning, Consultant

≤

Typical internal electrolysis cell

Typical dual anode cell

D.R Browning, Consultant

Classical cell types (a) Constant current (top) and controlled potential (bottom) cells (b) Cell for constant current electrolysis with mercury cathode Source: Ref 10

Table 1 Electrogravimetric determination of some metals using vibrating electrodes

Table 2 Determination of copper using internal electrolysis

Automatic potentiostat for controlled-potential analysis The cell emf may be varied automatically using this type of device Source: Ref 11

D.R Browning, Consultant

D.R Browning, Consultant

Table 3 Determination of Ni in NiCl 2 solution

D.R Browning, Consultant

Estimated Analysis Time

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

Potentiometric titration curves (a) Direct (b) First derivative (c) Second derivative

∆ ∆

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

Coulometric titration cell A, sparge gas inlet tube (sometimes not needed); B, generator electrode; C, isolation tube; D, auxiliary electrode; E, gas escape groove; F, stirrer bar; G, magnetic stirrer; XX, suitable indicating system

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

John T Stock, Department of Chemistry, University of Connecticut

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Table 1 Types of reactions in controlled-potential electrolysis and applicable Nernst equations

Apparatus for controlled-potential coulometry

Completeness of reaction as a function of potential for the reversible reduction of a metal ion species to

another soluble species E is the control potential required for 99.9% conversion of M(m) to M(m-n)

Table 2 Metals determined by controlled-potential coulometry

M M

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Current-time curves for the reduction of Ag+ to Ag(s) and Au3+ to Au(s) on a platinum electrode

Electrolysis conditions: silver, 0.1 M H2SO4, E = +0.16 V versus SCE; gold, 0.5 M HCl, E = +0.48 V versus SCE

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Jackson E Harrar, Chemistry and Materials Science Department, Lawrence Livermore National Laboratory

Walter T Smith, Jr., Department of Chemistry, University of Kentucky

Walter T Smith, Jr., Department of Chemistry, University of Kentucky

Identification of Organic Compounds

Determination of the Empirical Formula

Determination of the Composition of a Mixture

Sample Preparation

Combustion Method for Carbon, Hydrogen, and Nitrogen

Kjeldahl Method for Nitrogen (Ref 1)

α

Schöniger Flask Method for Other Common Elements

Walter T Smith, Jr., Department of Chemistry, University of Kentucky

Purity Determination

Composition of a Mixture

Characterization of an Unknown

Acids*

Alcohols

Aldehydes and Ketones

Amines