Platinum bright

Pt—Q—Salt, [Pt(NH3)2(HP04)] and [Pt(OH)3] (259,260). Chloride-based baths have been superseded by P-Salt-based baths, which are more stable and relatively easily prepared. Q-Salt baths offer even greater stabiUty and produce hard, bright films of low porosity. Plating under alkaline conditions employs salts of [Pt(OH3)] . These baths are easily regenerated but have low stabiUty. Platinum films have uses in the electronics industry for circuit repair, mask repair, platinum siUcide production, and interconnection fabrication (94). Vapor deposition of volatile platinum compounds such as [Pt(hfacac)2] and... 

Palladium proved especially useful in the hydrogenation of 2-hydroxy-3-nitropropanoic acid. Reduction over palladium-on-carbon gave pure, powdery isoserine, whereas platinum failed to reduce the nitro function under neutral or acidic conditions reduction over Raney nickel gave a bright green powder (96). 

Potentiometric titration using a bright platinum-saturated calomel electrode system this can be used when the reaction involves two different oxidation states of a given metal. 

Prepare 250 mL of 0.02 M potassium dichromate solution and an equal volume of ca 0.1 M ammonium iron(II) sulphate solution the latter must contain sufficient dilute sulphuric acid to produce a clear solution, and the exact weight of ammonium iron(II) sulphate employed should be noted. Place 25 mL of the ammonium iron(II) sulphate solution in the beaker, add 25 mL of ca 2.5M sulphuric acid and 50 mL of water. Charge the burette with the 0.02 M potassium dichromate solution, and add a capillary extension tube. Use a bright platinum electrode as indicator electrode and an S.C.E. reference electrode. Set the stirrer in motion. Proceed with the titration as directed in Experiment 1. After each addition of the dichromate solution measure the e.m.f. of the cell. Determine the end point (1) from the potential-volume curve and (2) by the derivative method. Calculate the molarity of the ammonium iron(II) sulphate solution, and compare this with the value calculated from the actual weight of solid employed in preparing the solution. 

Figure 4.28. STM image of a PtRh(lOO) surface. Although the bulk contains equal amounts of each element, the surface consists of 69% of platinum (dark) and 31 % of rhodium (bright), in agreement with the expected surface segregation of platinum on clean Pt-Rh alloys in ultrahigh vacuum. The black spots are due to carbon impurities. It is seen that platinum and rhodium have a tendency to cluster in small groups of the same elements.

Samples A and B are of particular Interest because they are composed of small, uniform platinum crystallites. The fact that these crystallites are on alumina limits the techniques available for their characterization. Sample A showed what appeared to be very thin platinum crystallites, which were barely observable by Imaging techniques or measurable by EDS. An exanq>le of a bright field Image and corresponding EDS analysis Is shown In Figure 1. In order to obtain analyses of this type, focus variation at magnifications of 1 to 4 Mx was commonly used with EDS analysis at 20 Mx to confirm that the particle was platinum. 

Dip the platinum loop in the solution and stick it in the flame. The result is a bright yellow glow. The color comes from two yellow emission lines that dominate the spectrum of sodium. The emission lines result from electrons dropping from the 3p to the 3s orbital. The two lines are very close to one another. The difference in energy is due to the slightly different energies of the electrons in the 3p orbital because of their spin. 

Fig. 5.44 The voltammogram of molecular hydrogen at a rotating bright platinum disk electrode in 0.5 m H2S04, pHl = 105 Pa, 25°C. The rotation speed

The structure of the metal particles dispersed on a silica powder support ( Aerosil 380, 70 A average silica particle diameter) has been studied by Avery and Sanders (47) using electron microscopy in both bright and dark field, to determine the extent to which the metal particles were multiply twinned or of ideal structure. Platinum, palladium, and gold were examined. These catalysts were prepared by impregnation using an aqueous solution of metal halide derivatives, were dried at 100°-150°C, and were hydrogen... 

Figure 3.10 Plots of current density vs. (exp( — 2t F/RT) — 1) for the evolution of hydrogen on bright platinum. From Schuldiner (1959)...

An interesting catalyst is the platinum supported on graphite. Fig. 12 shows a bright field image. The... 

Conductivity measurements were carried out in a high vacuum cell in the shape of an inverted cone provided with a phial breaking device [13] and with bright platinum... 

Carrying out the Combustion.—After introducing the substance adjust the precision clip so that a current of oxygen passes at the rate of 7 to 9 c.c. per minute (calibration of the bubble-counter with the aspirator, cf. p. 59) and heat the platinum catalysts to bright red heat with the tube burner. As soon as this degree of heat has been attained push the small roll of wire gauze to within a few... 

The ruthenium(II) polypyridyl complexes are also popular but the brightnesses do not exceed 15,000 and thermal quenching is rather significant. This property can be utilized to design temperature-sensitive probes providing that the dyes are effectively shielded from oxygen (e.g., in polyacrylonitrile beads). Despite often very high emission quantum yields the visible absorption of cyclometallated complexes of iridium(III) and platinum(II) is usually poor (e < 10,000 M-1cm-1), thus,... 

Wu et al. [31] have recently presented a novel concept of designing oxygen nanosensors. They used the precipitation method to obtain polyfluorene beads (0 25 nm) doped with the oxygen indicator platinum(II) octaethylporphyrin. Poly (9,9-dihexylfluorene) belongs to materials widely used in OLEDs and has a bright blue emission when excited in the UV region. In beads, FRET-mediated red emission... 

In fact, platinum oxide itself is the most likely contamination on the surface of a platinum electrode. Such layers of Pt02 are too thin to see under standard laboratory illumination, so these electrodes may still look bright and shiny. 

At Coventry we have electropolymerised styrene in the presence and absence of ultrasound (38 kHz) at 0°C and at two different currents (100 mA and 400 mA). We used bright platinum electrodes, dichloromethane as solvent and tetrabutyl ammonium boron hexafluoride (TBABF5) as the electrolyte. At 400 mA we obtained complete conversion in 150 min vhth a resultant molar mass of 100000 compared with 70% conversion and a molar mass of 314000 in the absence of ultrasound. 

Rhodium is one of the six platinum transition elements that include Ru, Rh, Pd, Os, Ir, and Pt. Of these metals, rhodium has the highest electrical and thermal conductivity. Although a relatively scarce metal, rhodium makes an excellent electroplated surface that is hard, wears well, and is permanently bright— ideal for plating the reflectors in automobile headlights. 

Platinum occurs in nature as a bright-white cubic crystalline solid with metallic luster associated with other noble metals of its group. Platinum also occurs as the mineral sperrylite, PtAs2, found as tin-white brittle cubic crystals containing 52-57% platinum in certain nickel-bearing deposits. Some other minerals of platinum are cooperite PtS (Pt 80-86%) and braggite(Pt, Pd, Ni)S (Pt 58-60%). The abundance of platinum in the earth s crust is estimated to be 0.005 mg/kg. 

Fig. 4 Potential versus current forthe reversible O2/H2O system on a bright platinum surface (Reproduced with permission from Ref 44).

Klaus obtained six grams of the new metal from osmiridium, the portion of the crude platinum which is insoluble in aqua regia. He calcined a mixture of osmiridium, potash, and potassium nitrate in a silver crucible placed inside a Hessian crucible on a layer of magnesia (27). After heating it for an hour and a half at bright redness, he poured the molten contents into an iron capsule. He then took up the melt in a very large volume of water, and allowed it to stand four days in the dark in a completely filled bottle. 

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