Palladium hydrogen absorbed

Some 100 years after Cavendish s discovery of hydrogen, and only 3 years after it was realized that hydrogen sorbed from chemical or electrochemical sources causes blistering and embrittlement to steel vessels, Graham [29] observed the ability of palladium to absorb hydrogen and wrote in Philosophical Transactions of the Royal Society of London ... 

The sensitivity of the system permitted the determination of the magnetic values to an accuracy of better than 1%. The amounts of hydrogen absorbed were probably accurate to about 10% on the gels carrying the least palladium and probably better than 1% for the gels carrying the most metal. 

Sieverts has studied the absorption of hydrogen from 138° to 821° C. and with varying pressures of gas ranging from 1 mm. to 760 mm. He observed that the amount of hydrogen absorbed per unit weight of palladium is nearly proportional to the square root of the hydrogen pressure. 

In further support of this may be cited the observation of Sieverts,1 that the quantity of hydrogen absorbed by unit -weight of palladium is a function of the pressure and temperature only, and is quite independent of the superficial area of the metal. This would indicate that the absorption of nydrogen is an example of true solution rather than of definite chemical combination. 

When suspended in water palladium black absorbs even more hydrogen, namely, in one case 1204 times its own volume,3 Under similar conditions it likewise absorbs acetylene slowly when suspended in 60 per cent, alcohol it has a pronounced adsorptive action,4 as also when suspended in an aqueous solution of sodium protalbinate. The absorbed acetylene exhibits an enhanced chemical activity. The curves obtained by plotting the rate of absorption of hydrogen by platinum black are smooth, indicating that only one allotropic form of palladium is present.5... 

By a different type of side-chain condensation, the dimer 6995 was formed from l,2-dihydro-2,2,4-trimethylquinazoline in 0.1 N hydrochloric acid at 100°. Bimolecular reduction products have been produced when hydrogenating 3-acetamido-6-methoxy-5-nitropyridazine 2-oxide over palladium/charcoal two different products (70 and 71) have been isolated depending on the solvent used and the amount of hydrogen absorbed.96... 

At a given temperature T let us take a gramme of palladium and increase the mass m of hydrogen absorbed by this palladium. 

When the mass m of hydrogen absorbed by a gramme of palladium attains, then exceeds S, the hydrogenized palladium forms but a single solid solution the system again becomes bivariant the tension of the hydrogen increases with the richness of the solid solution the representative point describes a curve AB which rises from left to right. 

T.Ito T. Kadowaki (1975). Phys. Lett., 54A, 61-2. NMR of hydrogen absorbed in palladium black. 

The former authors proceeded in two ways, (a) The dibenzyliodide of AT-methylemetine on treatment with alkali effected a double ring scission to yield a product which on catalytic hydrogen absorbed 3 moles of hydrogen. Two of these were consumed in the rapid saturation of the double bonds and one in the slower hydrogenolysis of the V-benzyl radical to yield toluene. The unsaturated compound on thermal dehydrogenation at 300-310 in the presence of palladium generated... 

The third class of hydrides is the metallic, or interstitial, hydrides, which are formed when transition metal crystals are treated with hydrogen gas. The hydrogen molecules dissociate at the metal s surface, and the small hydrogen atoms migrate into the crystal structure to occupy holes, or interstices. These metal-hydrogen mixtures are more like solid solutions than true compounds. Palladium can absorb about 900 times its own volume of hydrogen gas. In... 

For instance, palladium can absorb 2800 times its volume forming the nonstoichiometric comound PdH . Hydrogen is only poorly soluble in water with a solubility of 0.00175 mol.% at NTP but it is more soluble in efhanol (0.0180 mol.%) and other organic solvents. 

Full characterization of hydrogen absorbing materials requires the determination of the hydrogen concentration. For bulk materials this is not a particular problem since even standard weighing techniques will often suffice. Thin films present more difficulty simply because of the small amount of material available. The purpose of this paper is to describe two techniques which are useful for measuring hydrogen concentration in thin films. We will describe their application to the palladium-hydrogen system. 

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