Bismuth diagram

The potassium/caesium phase diagram is an example of a system involving the formation of mixed crystals with a temperature minimum (Fig. 4.4). The right and left halves of the diagram are of the same type as the diagram for antimony/bismuth. The minimum corresponds to a special point for which the compositions of the solid and the liquid are the same. Other systems can have the special point at a temperature maximum. 

Figure S.2 shows a schematic diagram of the automatic hydride/vapour-generator system designed by P.S. Analytical. This has been widely used to determine hydrideforming elements, notably arsenic, selenium, bismuth, tellurium and antimony, in a wide range of sample types. To provide a wide range of analyses on a number of matrices the chemistry must be very well defined and consistent. Goulden and Brooksbank s automated continuous-flow system for the determination of selenium in waste water was improved by Dennis and Porter to lower the detection levels and increase relative precision [10, 11]. The system described by Stockwell [9] has been specifically developed in a commercial environment using the experience outlined by Dennis and Porter.

Figure 2. Compositional diagram for the preparation of bismuth molybdate catalysts using the HI AD process configuration shown in Figure 1 at 900°C using air as make up gas. Plot is of concentrations of bismuth used in the reacting solution vs arc plasma analyzed concentrations of the finished catalysts directly fi-om HTAD reactor Circles Co-precipitation prepared materials. Triangles Up flow prepared aerosol materials. Squares. Down flow prepared aerosol materials.

Figure 31. Flow diagram for the production of bismuth vanadate molybdate pigment a) Reaction vessel b) Filter c) Dryer d) Furnace treatment...

Fig. 2.19. Schematic diagram to illustrate the growth process of the NiBi and NiBi3 intermetallic compound layers between nickel and bismuth ...

As the necessary sulfur activity data are available, a ternary diagram can easily be constructed. Bismuth has a lower affinity to sulfur than tungsten, thus bismuthinite would immediately react with tungsten ... 

Cadmium (m.p. 321° C) and bismvuh (m.p. 271° C) do not form solid solutions nor compounds with one another. Their eutectic point lies at 6 weight percent bismuth and C. Sketch their phase diagram, and label each region to show what phases are present. 

Fig. 11 A caking diagram showing the flocculation of a bismuth subnitrate suspension by means of the flocculating agent, potassium monobasic phosphate.

Figure 15.10 Diffraction diagrams of a high pressure modification of bismuth. The lower diagram shows diffraction data recorded with a conventional sealed source, the upper one data measured with synchrotron radiation (unpublished results).

Our recent work on the bismuth-cerium molybdate catalyst system has shown that it can serve as a tractable model for the study of the solid state mechanism of selective olefin oxidation by multicomponent molybdate catalysts. Although compositionally and structurally quite simple compared to other multiphase molybdate catalyst systems, bismuth-cerium molybdate catalysts are extremely effective for the selective ammoxidation of propylene to acrylonitrile (16). In particular, we have found that the addition of cerium to bismuth molybdate significantly enhances its catalytic activity for the selective ammoxidation of propylene to acrylonitrile. Maximum catalytic activity was observed for specific compositions in the single phase and two phase regions of the phase diagram (17). These characteristics of this catalyst system afford the opportunity to understand the physical basis for synergies in multiphase catalysts. In addition to this previously published work, we also include some of our most recent results on the bismuth-cerium molybdate system. As such, the present account represents a summary of our interpretations of the data on this system. 

The maximum in catalytic activity observed for the multiphase region of the phase diagram necessarily arises from interactions between the separate phases. The bismuth rich and cerium rich solid solutions can readily form coherent interfaces at the phase boundaries due to the structural similarities between the two phases which can permit epitaxial nucleation and growth. A good lattice match exists between the [010] faces of the compounds, this match is displayed in Figure 6. We have also shown that regions of an [010] face of a Ce doped bismuth molybdate crystal resembles cerium molybdate compos tionally. This means that the interface between the two compounds need not have sharp composition gradients. It is structurally possible for the Bi-rich phase to possess a metal stiochiometry at the surface that matches that of the Ce-rich phase. 

Figure V-13 The phase diagram bismuth-selenium. After [94CHI/SHE]. Reprinted from [94CH1/SHE] with permission from the authors and Kluger/Plenum Publishers.

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