Platinum absorption

Toxicology, Pharmacology and Metabolism. The dose-limiting toxicity of AMD473 in mice (and rats) is myelosuppression (leukopenia and thrombocytopenia). No renal-, liver- or neuro-toxicity has been observed [54]. Platinum pharmacokinetics following i.v. administration to mice (20 mg/kg) showed a biexponential decay in plasma with a rapid distribution (f1/2a °f 24 min) followed by a slow elimination (ti/2p of 44 h). Following oral dosing, platinum absorption was rapid (rmax of 0.5h) with a bioavailability of 40% [54]. Platinum accumulated mainly in the liver, kidney and spleen [54]. 

Dual-Pressure Process. Dual-pressure processes have a medium pressure (ca 0.3—0.6 MPa) front end for ammonia oxidation and a high pressure (1.1—1.5 MPa) tail end for absorption. Some older plants still use atmospheric pressure for ammonia conversion. Compared to high monopressure plants, the lower oxidation pressure improves ammonia yield and catalyst performance. Platinum losses are significantiy lower and production mns are extended by a longer catalyst life. Reduced pressure also results in weaker nitric acid condensate from the cooler condenser, which helps to improve absorber performance. Due to the spHt in operating conditions, the dual-pressure process requires a specialized stainless steel NO compressor. 

Silicon—Ca.rbon Thermoset. The Sycar resins of Hercules are sihcon—carbon thermosets cured through the hydrosilation of sihcon hydride and sihcon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (<15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type apphcations. 

COMPARISON OF MICROWAVE ASSISTED EXTRACTION METHODS FOR THE DETERMINATION OF PLATINUM GROUP ELEMENTS IN SOIL SAMPLES BY ELECTROTHERMAL ATOMIC ABSORPTION SPECTROMETRY AFTER PHASE SEPARATION-EXTRACTION... 

An interesting field of application is the protection of tantalum against hydrogen embrittlement by electrical connection to platinum metals. The reduction in hydrogen overvoltage and the shift of the free corrosion potential to more positive values apparently leads to a reduced coverage by adsorbed hydrogen and thereby lower absorption [43] (see Sections 2.1 and 2.3.4). 

Dicyclopentadiene (50 g, 0.38 mole) is dissolved in 100 ml of anhydrous ether. Platinum oxide (0.25 g) is added, and the mixture is hydrogenated in a Parr apparatus at an initial pressure of 50 psi. Initially the reaction mixture becomes warm. The absorption of 2 mole equivalents of hydrogen takes 4-6 hours. The mixture is filtered by suction to remove the catalyst, and the filtrate is distilled at atmospheric pressure through a short fractionating column. 

Hydroxylamines ordinarily do not accumulate in the reduction of aromatic nitro compounds for, with some exceptions, most systems in competition will reduce the hydroxylamine function preferentially. Nonetheless, systems have been found that afford the intermediate aromatic hydroxylamine in excellent yield. With hydrogen gas as a reductant and platinum-on-carbon or -on-alumina and about I wt % of DMSO based on nitro compound as a modifier, aromatic hydroxylamines can be formed in 90% yield under mild conditions. The reduction slows markedly after absorption of the second mole of hydrogen and should be stopped at this stage (80). 

Selective reduction of 11 to 12 is achieved in high yield by the use of 5% Rh-on-C in DMF containing NH OH. Reduction essentially stops after absorption of 3 mol of hydrogen. Yields were lower in ethanol. Platinum oxide in ammonical DMF showed fair selectivity, but Pd-on-C none. In a typical experiment, 0.1 mol of 11 in 250 ml DMF containing 3 ml 28% NH4OH solution and 0.7 g 5% Rh-on-Al O was reduced at 40 psig until 0.3 mol of hydrogen were absorbed (2). 

The flask of a Parr hydrogenation apparatus was charged with 10,5 g of 3,3-diphenylpropyl-amine, 7.7 g of cyclohexylacetone, 50 ml methanol and 150 mg of platinum dioxide. Hydrogen at a pressure of 3 atmospheres was introduced and the mixture stirred. Upon absorption of the theoretical amount of hydrogen, stirring is discontinued, the catalyst is filtered off and the solution is evaporated to dryness. The residue is taken up with ether and the hydrochloride is precipitated with HCI in alcoholic solution. The product, as collected on a filter and washed with ether, is recrystallized from isopropanol. Yield 17 g (92.5% of theory). 

A solution containing 26.3 mg of vitamin 6,2 in 15 ml of water was shaken with 78 mg of platinum oxide catalyst and hydrogen gas under substantially atmospheric pressure at 25 C for 20 hours. Hydrogen was absorbed. During the absorption of hydrogen the color of the solution changed from red to brown. The solution was separated from the catalyst and evaporated to dryness in vacuo. The residue was then dissolved in 1 ml of water and then diluted with about 6 ml of acetone. 

Niobium like tantalum relies for its corrosion resistance on a highly adherent passive oxide film it is however not as resistant as tantalum in the more aggressive media. In no case reported in the literature is niobium inert to corrosives that attack tantalum. Niobium has not therefore been used extensively for corrosion resistant applications and little information is available on its performance in service conditions. It is more susceptible than tantalum to embrittlement by hydrogen and to corrosion by many aqueous corrodants. Although it is possible to prevent hydrogen embrittlement of niobium under some conditions by contacting it with platinum the method does not seem to be broadly effective. Niobium is attacked at room temperature by hydrofluoric acid and at 100°C by concentrated hydrochloric, sulphuric and phosphoric acids. It is embrittled by sodium hydroxide presumably as the result of hydrogen absorption and it is not suited for use with sodium sulphide. 

Measurements were performed on a potassium nitrite melt (KNO3) at 450°C. Fig. 73, curve 1 presents the spectrum obtained for a melt layer 0.05-0.1 mm thick, which was placed on a reflective surface (polished platinum). Fig. 73, curve 2 presents the inverted spectrum (relative to curve 1) of a relatively thin layer placed on an absorptive bottom surface (carbon-glass). 

Fig. 1-18. The L spectra of platinum. Reference to the L levels labeled at the lower right-hand corner of this figure shows that none of the lines occurs on the short-wravelength side of the corresponding absorption edge. -Note also that some of the Bragg peaks contain lines from more than one L level. os...

Infrared absorption studies of CO on platinum shows two bands near... 

Very few studies on complexes of palladium and platinum with 1,1-dithiolato ligands have been reported recently. The electronic absorption spectra of the Et2dtc complexes of Pd and Pt, as well as Zn, Cu, Fe, Co, and Mn, have been measured in MeCN, EtOH, and -heptane, with diffuse-reflectance spectra also being determined (401). In 1969 and... 

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