Platinum solution saturated with

Catalytic synthesis of hydroxylamine from nitrogen oxide and hydrogen is widely used in industry as a constituent part of caprolactam production. The reaction is conducted in aqueous sulfuric acid solution saturated with NO and H2 at 40°C and a pressure of approximately 1 atm. Platinum supported on porous graphite, in the form of fine particles suspended in the intensely stirred solution, is used as a catalyst. The main direction of the reaction is... 

Reference electrode — Figure 1. Hydrogen electrode, (1) platinized platinum, (2) acid solution saturated with H2... 

The tetrachloroquinone (chloranil)/tetrachlorohydroquinone system has been used as a reference electrode in alcohols and acetic acid [222], often in the presence of an excess mineral acid. The half-cell consisted of a platinum electrode in a solution saturated with respect to both chloranil and the hydroquinone. The electrode is well poised, and at constant temperature and constant hydrogen ion activity the potential is stable. 

On the right side of the membrane, a 0.1 M sodium bicarbonate solution (saturated with carbon dioxide) is in contact with the palladium. A potentiostat holds this side of the membrane at a constant potential with respect to a Ag/AgCl reference electrode. A platinum... 

An observation that will help to find a probable mechanism is that if one plunges a platinum electrode into a solution saturated with propane and current passes at first and by knowing the coulombs involved, and assuming that the current comes from the following reaction ... 

What is the pH of a solution saturated with quinhydrone if the potential of a platinum electrode in the solution, measured against a saturated calomel electrode, is —0.205 V Assume the liquid-junction potential to be zero. 

In the case of standard electrode potential, it is appropriate to have a standard electrode whose reversible potential is made arbitrarily zero and against which the potentials of other electrodes can be measured. The hydrogen electrode is an accepted standard. It is composed of a rod of platinum covered with platinum black saturated with hydrogen gas at atmospheric pressure. Electrode potential based on this zero are said to refer to the hydrogen scale. However, in experimental work, it is often more suitable to use another standard electrode. Calomel is a common example. It consists of a pool of mercury covered with calomel (mercurous chloride) and immersed in a solution of potassium chloride. 

Irreversibly established rest potential, also called open-circuit potential, experimentally obtained in O2 saturated solutions varies for different electrode materials. On the most active platinum in pure acid solution saturated with O2... 

DMSO (dimethyl siilphoxide) solution and the anode solution is a water-DMSO solution saturated with potassium iodide. Ihe cathode is a platinum wire, while the anode is a silver rod. As the pK of the thymolphthalein indicator used to sense the pH in the titration cell is temperature-dependent, the titration cell should be kept at a constant temperature (within 0.2 °C) to achieve maximum precision. This can be done either by water-jacketing the titration cell, or by continuously blowing air of constant temperature around the cell. 

Although it is difficult to establish the equilibrium of reactions 4 and 9, reaction 13 is reversible on mercury [9], silver [28], carbon [7], and platinum [20] in alkaline electrolytes. Measurements [94] of the H2O2 oxidation and reduction on a degassed platinum electrode indicate the reversibility of reaction 12 in acid solution. It is clear from the preceding comments that small traces of H2O2 exert a considerable influence on the open-circuit potential in solutions saturated with O2. 

The reversible cell considered is represented in Fig 2 It is formed by a silver—silver iodide electrode a solution and a platinum electrode saturated with hydrogen at one atmosphere. The reversible E M F. is given by E. 

To set up a saturated calomel electrode, a saturated solution of potassium chloride is first prepared from pure potassium chloride and de-ionised water, and this is then shaken for some hours with analytical grade mercury(I) chloride so that the solution is also saturated with this substance. Pure mercury is placed in the electrode vessel to a depth of about 1 cm the platinum contact must be... 

This electrode is perhaps next in importance to the calomel electrode as a reference electrode. It consists of a silver wire or a silver-plated platinum wire, coated electrolytically with a thin layer of silver chloride, dipping into a potassium chloride solution of known concentration which is saturated with silver chloride this is achieved by the addition of two or three drops of 0.1M silver nitrate solution. Saturated potassium chloride solution is most commonly employed in the electrode, but 1M or 0.1 M solutions can equally well be used as explained in Section 15.1, the potential of the electrode is governed by the activity of the chloride ions in the potassium chloride solution. 

The procedure may be illustrated by the actual results obtained for the potentiometric titration of 25.0 mL of ca 0.1 M ammonium iron(II) sulphate with standard (0.1095M) cerium(IV) sulphate solution using platinum and saturated calomel electrodes ... 

Exchange reactions between bulk and adsorbed substances can be studied by on-line mass spectroscopy and isotope labeling. In this section the results on the interaction of methanol and carbon monoxide in solution with adsorbed methanol and carbon monoxide on platinum are reported [72], A flow cell for on-line MS measurements (Fig. 1.2) was used. 13C-labeled methanol was absorbed until the Pt surface became saturated. After solution exchange with base electrolyte a potential scan was applied. Parallel to the current-potential curve the mass intensity-potential for 13C02 was monitored. Both curves are given in Fig. 3.1a,b. A second scan was always taken to check the absence of bulk substances. 

After the chromium (II) chloride solution has been transferred to flask B, the flow of ammonia through the reaction vessel should be started. The ammonia delivery tube should approach but not dip below the liquid level in flask B. If tank ammonia is used, the tank should be opened carefully to avoid spattering of liquids by a sudden burst of gas. If ammonia is to be generated, the ammonium sulfate solution should be added carefully to the potassium hydroxide in flask C. It may be necessary to cool flask C with ice at first, then to warm the generator later in order to maintain a reasonably constant flow of ammonia. The use of tank ammonia avoids these problems. If zinc was used in the reduction, a precipitate of zinc hydroxide forms first and redissolves. The violet-blue solution stirred at 0° is saturated with ammonia, then a 2- to 3-g. sample of the platinum catalyst is added rapidly to flask B. A strong countercurrent of nitrogen is used to prevent entrance of air into the system when the catalyst is added. The reaction mixture is allowed to stir for one hour while the flask is cooled with ice. 

In the indirect amperometric method [560], saturated uranyl zinc acetate solution is added to the sample containing 0.1-10 mg sodium. The solution is heated for 30 minutes at 100 °C to complete precipitation. The solution is filtered and the precipitate washed several times with 2 ml of the reagent and then five times with 99% ethanol saturated with sodium uranyl zinc acetate. The precipitate is dissolved and diluted to a known volume. To an aliquot containing up to 1.7 mg zinc, 1M tartaric acid (2-3 ml) and 3 M ammonium acetate (8-10 ml) are added and the pH adjusted to 7.5-8.0 with 2 M aqueous ammonia. The solution is diluted to 25 ml and an equal volume of ethanol added. It is titrated amperometrically with 0.01 M K4Fe(CN)6 using a platinum electrode. Uranium does not interfere with the determination of sodium. 

Fig. 10 relates the composite extraction index (see above) obtained in the low-shear aqueous test system for these Tween surfactants, and adhesion tensions measured against various solids. Adhesion tensions against platinum and bitumen saturated pyrophyllite are irregularly related to tar sand extraction, while the adhesion tension against a fresh pyrophyllite surface is linearly (inversely) related to tar sand extraction. This is the first linear correlation between a measurable property of a surfactant solution and tar sand extraction which we have been able to obtain, and there appears to be no such finding in the literature. Fig. 11 gives the relations between extraction of bitumen with the paddle mill, solvent-aqueous-surfactant extraction and adhesion tensions measured against platinum, bitumen saturated pyrophyllite and hydrated (48 hours in water) pyrophyllite. 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

The universally accepted primary reference half-cell is the standard hydrogen electrode. The electrode consists of a noble metal (platinized platinum) dipping into a solution of hydrogen ions at unit activity and saturated with hydrogen gas at 1 bar (i.e. 1 X 105 Pa, which in practical terms may be taken to be equal to 1 atmosphere). In practice such a standard electrode cannot be realized, but the scale it defines can. 

The ZrOg sensor investigated at Temple University responds to pH and is insensitive to the Eh of the solution. However, the bare platinum wire used to complete the circuit in the test chamber will respond to changes in the Eh conditions. It is believed that a linear relationship between pH and EMF was observed in this experiment because the test solutions employed were all air-saturated and therefore had similar Eh values. This hypothesis was tested by sequentially pumping three identical sets of pH buffer solutions through the test chamber. In the first calibration, the solutions were saturated with oxygen gas in the second calibration, the solutions were saturated with hydrogen gas in the third calibration, the solutions were saturated with air. There was a several hundred millivolt shift in the EMF in response to these three sets of solutions however, in each calibration the pH versus EMF response was linear. Clearly,... 

---