Potentiostat tubes

Anodic protection today allows safe and efficient protection of air coolers and banks of tubes in sulfuric acid plants. In 1966 the air cooler in a sulfuric acid plant in Germany was anodically protected. Since then more than 10,000 m of cooling surfaces in air- and water-cooled sulfuric acid plants worldwide have been protected. The dc output supply of the potentiostats amounts to >25 kW, corresponding to an energy requirement of 2.5 W per m of protected surface. As an example. Fig. 21-9 shows two parallel-connected sulfuric acid smooth tube exchangers in a production plant in Spain. 

Within the scope of thermoelectric nanostructures, Sima et al. [161] prepared nanorod (fibril) and microtube (tubule) arrays of PbSei. , Tej by potentiostatic electrodeposition from nitric acid solutions of Pb(N03)2, H2Se03, and Te02, using a 30 fim thick polycarbonate track-etch membrane, with pores 100-2,000 nm in diameter, as template (Cu supported). After electrodeposition the polymer membrane was dissolved in CH2CI2. Solid rods were obtained in membranes with small pores, and hollow tubes in those with large pores. The formation of microtubes rather than nanorods in the larger pores was attributed to the higher deposition current. 

Potentiostat, (typically, Echochemie, Autolab PGSTAT), Schlenk tube x 2, aluminum sheet, mild steel rods, P400 sand paper, anhydrous AICI3, l-butyl-3-methyl imidazolium chloride ([BMIM]C1), toluene, acetone, dichloromethane, HC1, HNO3, H3PO4, acetic acid, isopropanol. 

The student will apply an impressed cathodic current to the entrance of the tube-tubesheet arrangement using a potentiostat in the conventional three-electrode arrangement with a counterelectrode (CE) and controlling reference electrode (RE). These electrodes will be placed at a distance from the tube-tubesheet arrangement as illustrated in Fig. 29. The working electrode (WE) consists of 304 stainless steel, the RE is a saturated calomel electrode (SCE), and the two test... 

Electrometer amplifier— An electronic amplifier with an extremely high -> input impedance (Rln > 1014 Q). The device allows measurements of electrical voltages (potentials) at practically zero current. Early devices employed specially designed and selected vacuum tubes (electrometer tubes) operated in a mode with very low grid current. The development of field effect transistors of various types allowed the application of solid-state devices. Electrometer amplifiers are employed in - pH meters (and generally in so-called pi meters, where I stands for ion), all types of instruments for po-tentiometric measurements and in the reference electrode input of -> potentiostats. Because of the high input impedance electrometer amplifiers are sensitive towards electric interferences, consequently some potentiostats have their -> reference electrode input circuitry (essentially an electrometer amplifier) mounted in a separate housing to be attached as close as possible to the reference electrode in order to minimize external interference. 

Fig.l View of a glass cell (capacity 5 to 7 ml of solution) connected to a power source (potentiostat). Case of a reduction at a copper cathode. A inlet for inert gas, B reference electrode like a saturated calomel electrode, C anodic compartment (a glass tube ended by a glass frit), D platinum grid as anode, E working electrode copper grid (area about 4 cm2), F inert gas outlet. The solution is stirred with a magnetic bar. Thus for an amount of electroactive compound (one-electron reduction) of 10 3 mol, electrolysis current could be of the order of 0.1 A and the reaction completed (until nil current) in much less than 1 hour. 

Chou et al. were the first to report a template-free, one-step method for synthesizing SnC>2 mesoscale tubes via an anodic deposition process.231 The anodic deposition of SnCh was conducted in a nitrate containing, chloride-based Sn bath with Pt as both cathode and anode substrate. The electrodeposition was performed under potentiostatic condition. 

The anodic protection technique now enables air coolers and tube bundles in sulfuric acid plants to be protected from corrosion reliably and economically. Anodic protection was provided for air coolers of sulfuric acid production plants for the first time in 1966. Since then, a combined cooler surface area exceeding 10,000 m in air-cooled and water-cooled sulfuric add plants has been protected in this way worldwide. The installed initial electrical direct current output of the potentiostats is >25 kW, corresponding to an energy requirement of 2.5 W/m for the surface needing protection (Kuron and Grafen 1988). 

A PAR Model 173 Potentiostat and a PAR Model 179 Digital Coulometer were used for controlled- potential electrolysis experiments. The potentiostat was connected to a PAR Model 175 Universal Programmer and a Houston Instruments Model 2000 X-Y Recorder for cyclic voltammetry experiments. A Perkin-Elmer Model 1710 FTIR Spectrophotometer and Varian Model E-9 ESR Spectrometer were used in spectroscopic measurements. For the ESR spectra taken in vacuum, the samples were filled in ESR tubes, pumped down to 10 torr for one hour, and sealed on a vacuum line. The ESR spectra were t en at room temperature. A Gammacell Model 220 Co gamma ray source was used for irradiation. 

Fig. 4.6 Hematite morphologies accessible by potentiostatic anodization The left (top and bottom) shows SEM images of structures from the work of Prakasam et al. [87] and the right (top and bottom) shows images of tubes from Rangaraju et al. [88]. SEM images used with permission from [87] and [88]...

The distance (and hence volume) between the confluence point of the sample and reagent streams and the detection cell needs to be optimized for the kinetics of the reaction used. The flow cell must be transparent to the wavelength of the chemiluminescence emission and inert to the chemical reaction or solvent system glass, quartz, and Teflon tubing are commonly employed. Instrumentation for electrogenerated chemiluminescence requires suitable electrodes and a potentiostat to facilitate and control the electrochemistry. Gold, platinum, or carbon working electrodes are placed in the observation cell with counter and reference electrodes situated downstream. 

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