Barium cathode

The work function for barium is 2.48 eV. If light having a wavelength of 400 nm is shone upon a barium cathode, what is the maximum velocity of the ejected electrons ... 

It is also important to note the effect of device architecture. In the case of compounds 36 and 37, the use of the standard hole transport material (HTL) PEDOTrPSS led to devices with low PCE. Use of metal oxide HTLs (nickel oxide or molybdenum oxide) significantly improved device performance by greater than 100%, and allowed for record efficiencies to be achieved. For compound 41, employing inverted device architectures, zinc oxide optical spacers, polyelectrolyte interlayers, and barium cathodes, all led to significant improvements in device PCE, with a record 9% being achieved. ... 

Zinc electrowinning Zinc in a sulfuric acid/ aqueous solution, lead-silver alloy anodes, aluminum cathodes, barium carbonate, or strontium, colloidal additives... 

The atomic absorption characteristics of technetium have been investigated with a technetium hollow-cathode lamp as a spectral line source. The sensitivity for technetium in aqueous solution is 3.0 /ig/ml in a fuel-rich acetylene-air flame for the unresolved 2614.23-2615.87 A doublet under the optimum operating conditions. Only calcium, strontium, and barium cause severe technetium absorption suppression. Cationic interferences are eliminated by adding aluminum to the test solutions. The atomic absorption spectroscopy can be applied to the determination of technetium in uranium and its alloys and also successfully to the analysis of multicomponent samples. 

In 1787 William Cruikshank (1745-1795) isolated, but did not identify, strontium from the mineral strontianite he examined. In 1790 Dr. Adair Crawford (1748—1794), an Irish chemist, discovered strontium by accident as he was examining barium chloride. He found a substance other than what he expected and considered it a new mineral. He named the new element strontium and its mineral strontianite after a village in Scotland. In 1808 Sir Humphry Davy treated the ore with hydrochloric acid, which produced strontium chloride. He then mixed mercury oxide with the strontium chloride to form an amalgam alloy of the two metals that collected at the cathode of his electrolysis apparatus. He heated the resulting substance to vaporize the mercury, leaving the strontium metal as a deposit. 

It is produced by the reduction of barium oxide (BaO), using aluminum or sihcon in a high-temperature vacuum. It is also commercially produced by the electrolysis of molten barium chloride (BaCy at about 950°C, wherein the barium metal is collected at the cathode and chlorine gas is emitted at the anode. 

Chemists did not discover the mineral witherite (BaCO ) until the eighteenth century. Carl Wilhelm Scheele (1742—1786) discovered barium oxide in 1774, but he did not isolate or identify the element barium. It was not until 1808 that Sir Humphry Davy used molten barium compounds (baryta) as an electrolyte to separate, by electrolysis, the barium cations, which were deposited at the negative cathode as metallic barium. Therefore, Davy received the credit for bariums discovery. 

Phthalimide was hydrogenated catalytically at 60-80° over palladium on barium sulfate in acetic acid containing an equimolar quantity of sulfuric or perchloric acid to phthalimidine [7729]. The same compound was produced in 76-80% yield by hydrogenation over nickel at 200° and 200-250 atm [43 and in 75% yield over copper chromite at 250° and 190 atm [7730]. Reduction with lithium aluminum hydride, on the other hand, reduced both carbonyls and gave isoindoline (yield 5%) [7730], also obtained by electroreduction on a lead cathode in sulfuric acid (yield 72%) [7730]. 

William Cruickshank in 1787 and Adair Crawford in 1790 independently detected strontium in the mineral strontianite, small quantities of which are associated with calcium and barium minerals. They determined that the strontianite was an entirely new mineral and was different from baryta and other barium minerals known at the time. In 1808, Sir Humphry Davy isolated strontium by electrolysis of a mixture of moist strontium hydroxide or chloride with mercuric oxide, using a mercury cathode. The element was named after the town Strontian in Scotland where the mineral strontianite was found. 

An example of the difficulties encountered when trying to fabricate an ohmic electrode, able to sustain a space-charge-limited current, is the recent work of the Neher group [179]. The authors deposited barium as an electron injection cathode on top of an electron transporting polymer based on a naphthalene diimide core whose LUMO is as low as 4 eV below vacuum level. Although the Fermi level of barium should be above the LUMO of the polymer, the electron current is. 

Nearly a century after Wohler and Bussy liberated beryllium, Alfred Stock and Hans Goldschmidt devised the first commercial process, in which a mixture of the fluorides of beryllium and barium is electrolyzed. The molten beryllium separates out at the water-cooled iron cathode (24). 

When the current is well adjusted, a dark-red color appears immediately around the anode, and the solution in the anode cell soon becomes dark red throughout. After about 2 hr., stop the action, remove the cathode cell, and dilute the anode solution with an equal volume of water. Filter on an asbestos mat, if necessary, and add a saturated solution of barium hydroxide or barium chloride as long as a red precipitate forms. Wash the precipitate several times by decantation with hot water, collect it on a filter, and wash it free of alkali. Dry at a temperature not to exceed 100°. The preparation is never very pure, and the yield is small. If at any time the electrodes become passive, reverse the current frequently for a few minutes at a time. 

The first three are illustrated by specific examples in the syntheses that follow. Sodium amalgam (synthesis 4) is readily prepared by direct combination of the metal with mercury (illustrating method 1). Barium amalgam (synthesis 5) can be produced readily by the electrolysis of a saturated aqueous solution of barium chloride with a mercury cathode (illustrating method 2a). Barium amalgam is also easily obtainable by the action of sodium amalgam upon a concentrated aqueous solution of barium chloride (illustrating method 3). 

It is by far the simpler method, gives a purer product, and is to be preferred to the displacement method. The directions given under procedure A are based essentially upon the results obtained by G. MePhail Smith and A. C. Bennett and involve the electrolysis of a saturated solution of barium chloride using a mercury cathode. The displacement method is given as an optional procedure. 

One hundred milliliters of a saturated solution of barium chloride is placed in a 250-ml. beaker, and 250 g. of pure mercury is added. Electrical contact with the latter, serving as the cathode, is made by means of a platinum wire fused through the end of a glass tube. A platinum foil (5 to 10 sq. cm.) bent at right angles, but parallel to the mercury cathode, is used as the anode. 

Bennett Mid his co-workeis [43] confirmed this interpretation of the cryometric investigations. To prove definitely the existence of the N02+ ion, they attempted to show that when electrolysed, the ion is transported towards the cathode. They did not succeed in obtaining full evidence for this, although they found that nitric acid moves away from the Miode. It was only when the electrolysis was carried out in the presence of oleum Mid barium salts, that the transport of nitric acid towards the cathode was confirmed. Studying the cathodic polMization of nitric acid Mint [44] observed the evolution of nitrogen dioxide at the cathode. This may be mi additional piece of evidence for the trMisport of mi ion containing nitrogen (probably N02+) towMds the cathode. 

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