Deposited metal, hydrogen content

Copper, silver, and gold colloids have been prepared by Chemical Liquid Deposition (CLD) with dimethoxymethane, 2-methoxyethyl ether, and ethylene glycol dimethyl ether. The metals are evaporated to yield atoms which are solvated at low temperatures and during the warm-up process colloidal sols with metal clusters are obtained. Evaporation of the solvent was carried out under vacuum-generating metal films. These films are showing very low carbon/hydrogen content and were characterized by elemental analyses and infrared spectroscopy (Cardenas et al., 1994). 

The metals deposited on substrates could catalyze the dehydrogenation reaction during the coking step leading to "cokes" of lower hydrogen content. Such low-hydrogen "coke" is known to react with steam more slowly. Thus, the metals could affect the... 

The total hydrogen content is defined for the present purposes as the sum of the diffusible and residual contents, the latter being determined by hot extraction at 650 °C under vacuum or in a carrier gas as described below. The results may be expressed in terms of the hydrogen content per unit weight of either deposited metal (i.e. the weld metal deposited on to the test specimen during the test) or fused metal (i.e. the metal deposited plus the parent metal in the test sample which has been melted by the welding operation). 

The volume measured is converted to 0°C and 760 mm. This volume, divided by one-hundredth of the gain in weight, is the diffusible hydrogen content, in mL/100 g deposited metal. 

The increase in weight of a parent material due to the deposition of filler metal is particularly used in tests to measure weld hydrogen contents. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

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