Solubility of platinum in aqueous solutions at 25°C and pHs 4 to 10 under oxidizing conditions

Platinum has been found to be mobile under supergene conditions, including placers and weathering profiles. To elucidate the nature of Pt mobility in supergene environments, the dissolution of platinum metal was investigated under physicochemical conditions similar to those found in such environments. The solubility of platinum metal was measured at 25°C in several systems: Pt-K-HC8H4O4-H2O (pH 4.02), Pt-Na-HCO3-Cl-H2O (pH 6.40), Pt-Na-K-H2PO4-HPO4-H2O (pH 6.90), Pt-Na-HCO3-H2O (pH 8.30), Pt-Na-OH-H2O (pH 8.54), and Pt-Na-HCO3-H2O (pH 9.91). The redox conditions of these experiments were relatively oxidizing, with measured Eh values ranging from +280 to +590 mV. The ionic strength of the aqueous solutions did not exceed 0.30 (molal scale). The interpretation of the solubility results, in terms of the following reaction and its equilibrium constant, Pt(s)+nH2O left right double arrow Pt(OH)2−nn+nH++2e− served to identify the importance of the hydroxylated complex PtOH+ in the pH range (4 to 10) and to determine its stability constant at 25°C. Linear regression of the solubility data using the function log [Pt]−2pe=n pH+log Kn yielded a value of 1.01 ± 0.07 for n, the average ligand number, and −31.76 ± 0.55 for the thermodynamic equilibrium constant of reaction. The resulting stability constant (β1) of PtOH+ (Pt2+ + OH− left right double arrow PtOH+) is 24.91 ± 0.50, assuming the same value of the free energy of formation of Pt2+, ΔGfo(Pt2+) as that given by Glushko et al. (Thermodynamic Constants of Matter, Academy of Science, USSR, 1972). The range of values of ΔGfo(Pt2+) proposed to date is +185.63 to +258.74 kJ/mol. The value of Glushko et al. (1972) (+244.11 kJ/mol) appears to fit better with our measurements at pH 4 to 10 and with those of Wood (Wood S. A., “Experimental determination of the hydrolysis constants of Pt2+ and Pd2+ at 25°C from the solubility of Pt and Pd in aqueous hydroxide solutions,” Geochim. Cosmochim. Acta 55, 1759–1767, 1991) at pH 9 to 15.5. Finally, according to these new measurements of the solubility of platinum, the recommended values for Gibbs free energy (ΔGfo, in kiloJoule per mole) of the different aqueous species of Pt are +244.11 (Pt2+), −55.96 (PtOH+), and −234.48 (Pt(OH)2(aq)). The integration of data from the literature for chloride and sulfate complexes was used to calculate the speciation of platinum in seawater and in solutions with variable chlorinity (0.1, 1, and 3 mol/L NaCl) at 25°C. These calculations showed that in the absence of strong ligands (i.e., S2O32−, CN−), the transport of platinum in supergene environments primarily occurs in the form of PtOH+ (90%) and Pt(OH)2(aq) (9.7%). Chloride complexes (PtCl42− and PtCl3−) account for less than 1% of the dissolved platinum. This study clearly shows that the hydroxylated complexes (PtOH+ and Pt(OH)2(aq)) can play a very important role in controlling platinum transfer mechanisms in surface fluids (soils, placers, weathering profiles, etc.). Because the charged species PtOH+ is largely predominant, the mobility and transfer of platinum can also be affected by adsorption-desorption mechanisms onto oxides and hydroxides

Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 1B: Concise review

Reports on the design process, support of the design process, IPAD System design catalog of IPAD technical program elements, IPAD System development and operation, and IPAD benefits and impact are concisely reviewed. The approach used to define the design is described. Major activities performed during the product development cycle are identified. The computer system requirements necessary to support the design process are given as computational requirements of the host system, technical program elements and system features. The IPAD computer system design is presented as concepts, a functional description and an organizational diagram of its major components. The cost and schedules and a three phase plan for IPAD implementation are presented. The benefits and impact of IPAD technology are discussed

Design criteria for flight evaluation. Monograph 4 - Control system evaluation

Methods and analyses for flight evaluation of control systems for multistage launch vehicle

Geobase Information System Impacts on Space Image Formats

As Geobase Information Systems increase in number, size and complexity, the format compatability of satellite remote sensing data becomes increasingly more important. Because of the vast and continually increasing quantity of data available from remote sensing systems the utility of these data is increasingly dependent on the degree to which their formats facilitate, or hinder, their incorporation into Geobase Information Systems. To merge satellite data into a geobase system requires that they both have a compatible geographic referencing system. Greater acceptance of satellite data by the user community will be facilitated if the data are in a form which most readily corresponds to existing geobase data structures. The conference addressed a number of specific topics and made recommendations

DABI: A data base for image analysis with nondeterministic inference capability

A description is given of the data base used in the perception subsystem of the Mars robot vehicle prototype being implemented at the Jet Propulsion Laboratory. This data base contains two types of information. The first is generic (uninstantiated, abstract) information that specifies the general rules of perception of objects in the expected environments. The second kind of information is a specific (instantiated) description of a structure, i.e., the properties and relations of objects in the specific case being analyzed. The generic knowledge can be used by the approximate reasoning subsystem to obtain information on the specific structures which is not directly measurable by the sensory instruments. Raw measurements are input either from the sensory instruments or a human operator using a CRT or a TTY

The application of remote sensing to resource management and environmental quality programs in Kansas

There are no author-identified significant results in this report

Advanced General Aviation Turbine Engine (GATE) study

The small engine technology requirements suitable for general aviation service in the 1987 to 1988 time frame were defined. The market analysis showed potential United States engines sales of 31,500 per year providing that the turbine engine sales price approaches current reciprocating engine prices. An optimum engine design was prepared for four categories of fixed wing aircraft and for rotary wing applications. A common core approach was derived from the optimum engines that maximizes engine commonality over the power spectrum with a projected price competitive with reciprocating piston engines. The advanced technology features reduced engine cost, approximately 50 percent compared with current technology