General purpose heat source

Fig. 3. The general purpose heat source assembly. Courtesy of the US. Department of Energy.

A. Schock, Design evolution and verification of the general purpose heat source. In Proc. o/15th Intersociety Energy Conv. and Eng. Con/., vol. 2, ASME, New York, 1980, pp. 1032 1042. 

The use of these devices is based on more than thirty years of operation experience on space vehicles of various types. As an example, the US Department of Energy (DoE) has up to now suppUed 44 radioisotope-powered thermoelectric generator systems, used in 24 space missions. The most recent thermoelectric generator built by the DoE, the General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG), (Fig. 26-1), produces 290 W of electric energy with less than 11 kg of plutonium dioxide. Three units are installed on the Cassini vehicle for the exploration of Saturn,... 

Electrospray is viewed as the most versatile ionization technique for neutral compounds and ions in solution, and at the same time a general-purpose interface for LC-MS [14-24]. In electrospray ions are formed in solution and then transferred to the gas phase. This differs from APCI where neutral molecules are first transferred to the gas phase and then ionized by gas-phase ion-molecule reactions. The heart of the electrospray source is a metal capillary through which the sample solution flows. A potential of 3-6 kV is applied to the capillary forming a spray of fine droplets directed towards a counter electrode with a sampling orifice located about 1-3 cm from the capillary tip. A positive potential is applied to the capillary to generate positive ions, and a negative potential for negative ions. To accommodate different liquid flow rates droplet formation is assisted by optimization of the orifice diameter of the capillary sprayer, the use of a coaxial gas flow, and heat to increase the rate of solvent evaporation. 

Evaporator may refer either to the type of constmction utilized or to the entire assemblage of equipment in a single installation. Thus a single multiple-effect evaporator may contain a number of effects of either the same or different evaporator types. An effect is a section of the evaporator heated by steam at one pressure and releasing vapor (water) at a lower pressure to another section. The term steam generally indicates the heat supply, whereas vapor means the material evaporated. Thus vapor from one effect becomes steam at the next effect. The term prime steam identifies the steam suppHed from an outside source to operate the evaporator (see also Steam). An effect may consist of several bodies, all operating at the same steam and vapor pressures. The purpose of more than one body in an effect may be to handle Hquor at different concentrations, or the result of size limitations or of additions to increase the capacity of an existing evaporator. 

GC-AAS has found late acceptance because of the relatively low sensitivity of the flame graphite furnaces have also been proposed as detectors. The quartz tube atomiser (QTA) [186], in particular the version heated with a hydrogen-oxygen flame (QF), is particularly effective [187] and is used nowadays almost exclusively for GC-AAS. The major problem associated with coupling of GC with AAS is the limited volume of measurement solution that can be injected on to the column (about 100 xL). Virtually no GC-AAS applications have been reported. As for GC-plasma source techniques for element-selective detection, GC-ICP-MS and GC-MIP-AES dominate for organometallic analysis and are complementary to PDA, FTIR and MS analysis for structural elucidation of unknowns. Only a few industrial laboratories are active in this field for the purpose of polymer/additive analysis. GC-AES is generally the most helpful for the identification of additives on the basis of elemental detection, but applications are limited mainly to tin compounds as PVC stabilisers. 

W. H. Wollaston discovered rhodium in 1803-04 in crude platinum ore. Although he did not definitely state the source of this ore, it must have come from South America the Russian platinum ores had not yet been discovered. Since the platina to be procured in this country, said Wollaston, generally contains small scales of gold intermixed, as well as a portion of the mercury which the Spaniards employ for the separation of the gold, the platina used for my experiments, after being by mechanical means freed, as far as possible, from all visible impurities, was exposed to a red heat for the purpose of expelling the mercury (9). 

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