Platinum asbestos

The platinum asbestos is removed by filtration and the product which has deposited on this catalyst is dissolved in water. Alcohol is added to the combined filtered solution and washings, and the mixture is cooled with ice to precipitate the product. A second crop of crystals may be obtained by concentrating the solution under vacuum at room temperature, then cooling and adding hydrochloric acid until the pH is below 1. The crystals are thoroughly washed with ethanol. 

A support-effect such as demonstrated in the classical case of platinum asbestos is of negligible importance with ammonia catalysts except with osmium and ruthenium. 

Platinum Asbestos 250-600 Methane Ethylene Acetylene Propene Pentane Benzene CO, and H,0. .. HCOOH (3)... 

Dihydrofuro[2,3-b] quinolines from nitrolactones by reductive ring closure s. 18, 547 Platinum-asbestos Pyrroles from aminofurans... 

Quartz attachment for a sample (in an aluminium foil capsule). 2 Magnetic bar. 3 Combustion chamber. 4 Porous filling d- 2 mm). 5 Platinum-asbestos. 6 COjO or corundum. 7 Silver. 8 Silver wool. 9 Silver chips. 10 Ring-shapedmembrane.lt Connecting tube to the absorption tube. 

A combustion method with 3r vimetric determinati of carbon dioxide after absorption on ascarite is described by Nunemaker and Shrader (12). 0.5 g finely divided sample is mixed with 0.5 g iron chips and 0.3 to 0.5 g brass, and is burnt at 1200°C in an oxygen stream in a sintercorundum boat fitting in a quartz tube. Before absorption, the combustion gases are purified in a tube filled with copper oxide, platinum asbestos and silver wool at 600°C. The method allows the determination of 50 to 10000 Mg/g carbon with an accuracy of 50 Mg/g. 

Preparation of 30 per cent, palladium or platinum catalysts (charcoal or asbestos carrier). 

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. 

Broadly speaking, the differences in effectiveness of palladium and platinum catalysts are very small the choice will generally be made on the basis of availability and current price of the two metals. Charcoal is a somewhat more efficient carrier than asbestos. 

This method involves very simple and inexpensive equipment that could be set up m any laboratory [9, 10] The equipment consists of a 250-mL beaker (used as an external half-cell), two platinum foil electrodes, a glass tube with asbestos fiber sealed m the bottom (used as an internal half-cell), a microburet, a stirrer, and a portable potentiometer The asbestos fiber may be substituted with a membrane This method has been used to determine the fluoride ion concentration in many binary and complex fluondes and has been applied to unbuffered solutions from Willard-Winter distillation, to lon-exchange eluant, and to pyrohydrolysis distil lates obtained from oxygen-flask or tube combustions The solution concentrations range from 0 1 to 5 X 10 M This method is based on complexing by fluonde ions of one of the oxidation states of the redox couple, and the potential difference measured is that between the two half-cells Initially, each cell contains the same ratio of cerium(IV) and cerium(tll) ions... 

Earlier investigators employed strong bases (sodium hydroxide, potassium hydroxide) or platinum on asbestos to... 

Balthis and Bailar6 obtained tris (ethylenediamine) chromium-(III) complexes by the oxidation of chromium(II) solutions, using a procedure somewhat similar to that used for the synthesis of cobalt (III) com plexes. Mori7 described the preparation of hexaamminechromium(III) salts from the oxidation of chromium (II) salts in the presence of ammonia. The results obtained in both syntheses have been erratic.8,9 Berman noted that the foregoing syntheses are rendered dependable by the use of a catalyst of activated platinum on asbestos. Schaeffer,100 in a subsequent study, independently used colloidal platinum as a catalyst but reported some difficulty in separating it from the product.106 The procedures recommended and described here are based on the use of platinized asbestos as the catalyst. 

Approximately 2 g. of shredded asbestos slurried in 15 ml. of water is added to a solution containing 10 g. of sodium formate in about 30 ml. of water the solution is boiled gently, then about 80 ml. of a 5% platinum(II) chloride solution is added. The solution is boiled until the platinum has been deposited. 

The platinized asbestos is filtered, washed once with 10% sulfuric acid, once with hot water, once with hot 5% hydrochloric acid, and finally with hot water until no test for chloride or sulfate is found. The product is dried at 110° and stored until needed in a covered container. Each gram of asbestos contains about 0.5 g. of platinum. 

The first explicit information appeared in 1953 in two U.S. patents (9) which showed that platinum black as well as platinized asbestos or silica were effective for addition of trichlorosilane to olefins. Platinum on charcoal was unusually active with trichlorosilane and acetylene, ethylene, butadiene, vinyl chloride, or vinylidene fluoride. Temperatures as low as 130°C were sometimes employed. 

Tenteleff Also spelled Tentelew. An early version of the Contact process for making sulfuric acid. The catalyst was platinum supported on asbestos. Invented in 1907 and operated by the Gesellschaft der Tentelewschen Chemischen Fabrik, St. Petersberg. 

Mkaline Fuel Cell The electrolyte for NASA s space shnttle orbiter fuel cell is 35 percent potassinm hydroxide. The cell operates between 353 and 363 K (176 and I94°F) at 0.4 MPa (59 psia) on hydrogen and oxygen. The electrodes contain platinnm-palladinm and platinum-gold alloy powder catalysts bonded with polytetraflnoro-ethylene (PTFE) latex and snpported on gold-plated nickel screens for cnrrent collection and gas distribution. A variety of materials, inclnding asbestos and potassinm titanate, are used to form a micro-porous separator that retains the electrolyte between the electrodes. The cell structural materials, bipolar plates, and external housing are nsnally nickel-plated to resist corrosion. The complete orbiter fuel cell power plant is shown in Fig. 24-48. 

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