Saturated solution reference electrode

The electroreductive cyclization of the furanone 118 (R = -(CH2)4CH=CH— COOMe Scheme 36) using a mercury pool cathode, a platinum anode, a saturated calomel reference electrode, and a degassed solution of dry CH3CN containing -Bu4NBr as the electrolyte, gave the spirocyclic lactones 119 and 120 in a ratio 1.0 1.1 (Scheme 37)(91T383). 

So-called combination electrodes may be purchased in which the glass electrode and the saturated calomel reference electrode are combined into a single unit, thus giving a more robust piece of equipment, and the convenience of having to insert and support a single probe in the test solution instead of the two separate components. 

Prepare an approximately 0.1 M silver nitrate solution. Place 0.1169 g of dry sodium chloride in the beaker, add 100 mL of water, and stir until dissolved. Use a silver wire electrode (or a silver-plated platinum wire), and a silver-silver chloride or a saturated calomel reference electrode separated from the solution by a potassium nitrate-agar bridge (see below). Titrate the sodium chloride solution with the silver nitrate solution following the general procedure described in Experiment 1 it is important to have efficient stirring and to wait long enough after each addition of titrant for the e.m.f. to become steady. Continue the titration 5 mL beyond the end point. Determine the end point and thence the molarity of the silver nitrate solution. 

Place the prepared copper acetate solution in the beaker and add 10 mL of 20 per cent potassium iodide solution. Set the stirrer in motion and add distilled water, if necessary, until the platinum plate electrode is fully immersed. Use a saturated calomel reference electrode, and carry out the normal potentiometric titration procedure using a standard sodium thiosulphate solution as titrant. 

In Nebraska, state regulations require that the chemical makeup of animal feed sold in the state be accurately reflected on the labels found on the feed bags. The Nebraska State Agriculture Laboratory is charged with the task of performing the analytical laboratory work required. An example is salt (sodium chloride) content. The method used to analyze the feed for sodium chloride involves a potentio-metric titration. A chloride ion-selective electrode in combination with a saturated calomel reference electrode is used. After dissolving the feed sample, the chloride is titrated with a silver nitrate standard solution. The reaction involves the formation of the insoluble precipitate silver chloride. The electrode monitors the decrease in the chloride concentration as the titration proceeds, ultimately detecting the end point (when the chloride ion concentration is zero). 

For cases directly comparable to the cyclization originating from (27) above, the yields of the product were not as high. However, a related reaction used in the synthesis of an 11-substituted dibenzo[a,d]-cycloheptenimine derivative was very successful as shown in Scheme 11 (Eq. 2) [32]. In this reaction, a controlled potential electrolysis of (33) led to the formation of the tetracyclic (34) in an 85% isolated yield. The reaction was performed on a 1 g scale using an undivided cell, a graphite felt anode, a stainless steel cathode, a saturated calomel reference electrode, and a 1% NaBF4 in 70 30 THF/water electrolyte solution. The electrolysis was scaled up further with the use of a flow cell. In this experiment, 200 g of (33) were oxidized in order to afford a 75% isolated yield of (34). 

For most potentiometric measurements, either the saturated calomel reference electrode or the silver/silver chloride reference electrode are used. These electrodes can be made compact, are easily produced, and provide reference potentials that do not vary more than a few mV. The silver/silver chloride electrode also finds application in non-aqueous solutions, although some solvents cause the silver chloride film to become soluble. Some experiments have utilised reference electrodes in non-aqueous solvents that are based on zinc or silver couples. From our own experience, aqueous reference electrodes are as convenient for non-aqueous systems as are any of the prototypes that have been developed to date. When there is a need to exclude water rigorously, double-salt bridges (aqueous/non-aqueous) are a convenient solution. This is true even though they involve a liquid junction between the aqueous electrolyte system and the non-aqueous solvent system of the sample solution. The use of conventional reference electrodes does cause some difficulties if the electrolyte of the reference electrode is insoluble in the sample solution. Hence, the use of a calomel electrode saturated with potassium chloride in conjunction with a sample solution that contains perchlorate ion can cause dramatic measurements due to the precipitation of potassium perchlorate at the junction. Such difficulties normally can be eliminated by using a double junction that inserts another inert electrolyte solution between the reference electrode and the sample solution (e.g., a sodium chloride solution). 

The three electrodes the working microelectrode, the saturated calomel reference electrode and the platinum auxiliary electrode are immersed in a 5 mmol L-1 deaerated ferricyanide solution. 

The potential of steel in a test solution at 25 °C was measured with a saturated calomel reference electrode (SCE) and found to be +34 mV. 

EDTA). In this application the M(OH2)l+ cation that is to be titrated forms a soluble EDTA complex that is appreciably less stable than the HgEDTA complex.141 The mercury electrode is constructed in a form like that of Figure 5.40a or b, and is used in conjunction with a saturated calomel reference electrode. The electrode is immersed in a solution that contains the ion to be titrated [M(OH2) +], and a few drops of 0.01 M HgY2- are added (where Y4-represents the EDTA anion). This establishes the potential of the mercury electrode according to the half-cell reaction... 

Example 8.9a. Solution Composition from Measured emf With an electrode pair consisting of an inert Pt and a saturated calomel reference electrode in a sample of a sediment-water interface of pH = 6.4 (25°C), a potential difference (emf) of 0.47 V is measured. The sediment contains solid amorphous Fe(OH)3, and we assume that the measured potential corresponds to an oxidation-reduction potential of the aquatic environment. 

Figure 21-9a shows a typical cell for measuring pH. The cell consists of a glass indicator electrode and a saturated calomel reference electrode immersed in the solution of unknown pH. The indicator electrode consists of a thin, pH-sensitive glass membrane sealed onto one end of a heavy-walled glass or plastic tube. A small volume of dilute hydrochloric acid saturated with silver chloride is contained in the tube. (The inner solution in some electrodes is a buffer containing chloride ion.) A silver wire in this solution forms a silver/silver chloride reference electrode, which is connected to one of the terminals of a potential-measuring device. The calomel electrode is connected to the other terminal. 

Calculate the potential of the ceU consisting of a hydrogen electrode (Eh, = 1 atm) and a saturated calomel reference electrode (a) in a solution of 0.00100 M HCl, (b) in a solution of 0.00100 M acetic acid, and (c) in a solution containing equal volumes of 0.100 M acetic acid and 0.100 M sodium acetate. Assume that activities are the same as concentrations. 

The stability constant of a complex of pyrophosphate with Ni (presumably NiPjO though this is not specified by the authors) was measured by an amperometric titration procedure. Small amounts of the nickel nitrate salt were titrated with the pyrophosphate in an ammonium nitrate buffer solution (0.1 M), adjusted to a pH value of 8 with aqueous ammonia. A Pb02 indicating electrode was used with a platinum foil coimter electrode and a saturated calomel reference electrode. The procedure was found to be very sensitive to pyrophosphate even in the presence of phosphate. 

For the analytical chemist, an experimentally useful scale of acidity should allow the interpretation of the most important and common measurements as, for example, those with a glass electrode and saturated calomel reference electrode. The operational definition of pH of an aqueous solution is... 

Figure 16.13 OPC vs. time curves for oxalate-doped (...), PSS-Na-doped (—) and SDS-Na-doped (...) PPy films immersed in 3.5% NaCI solution. The same amount of charge was used for the synthesis of films (2 C cm, i.e. 3 pm thick) the potential is referred to a saturated sulfate reference electrode (SSE). (Reprinted with permission from Eiectrochimica Acta, Role of doping ions in the corrosion protection of iron by polypyrrole films by N.T.L. EHen, B. Garcia, A. Pailleret and C. Deslouis, 50, 7-8, 1747-1755. Copyright (2005) Elsevier Ltd)...

KCl solutions for a range of gold electrode potentials varying between —700 and -FlOO mV versus a saturated calomel reference electrode. 

Fig. 2.29 CV results and corresponding deflection data for Pt IPMCs in 1 M H2SO4 solution with a scan rate of 5mV/s. SCE is abbreviation of the saturated calomel reference electrode. Reprinted from [Park et al. (2008)] with permission from Cambridge University Press.

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