Bismuth vapor pressure

The volatility of the reactants is a concern in some solid state syntheses. This may be a slight problem in bismuth cuprates synthesized at high temperatures because Bi2Os has an appreciable vapor pressure at these temperatures (i.e. 900-950°C) however, chemical analyses of samples of bismuth-based superconductors before and after reactions at temperatures up to 900°C indicate no detectable loss of bismuth. This problem is much more severe in the case of thallium chemistry. 

Bi2 (g). The vapor density data of Biltz and Meyer1-3 indicated that bismuth vapor at the boiling point is about Bi2+1 Bi. The vapor pressure data, for liquid bismuth, of Greenwood,3 Ruff and Bergdahl,1 Ruff and Mugdan,1 and Barus1-2 yield —4.48 for the heat of vaporization at the boiling point. We have corrected this value for the amount of dissociation. 

The following data were obtained in a study of the vapor pressure of mercury (pi) in equilibrium with bismuth amalgams at 321° C ... 

BON/PAS] Boncheva-Mladenova, Z., Pashinkin, A. S., Novoselova, A. V., Determination of the saturated vapor pressure of solid bismuth selenide, Inorg. Mater., 4, (1968), 904-907. Cited on pages 200, 201,202, 495. 

UST/VIG] Ustyugov, G. P., Vigdorovich, E. N., Timoshin, I. A., The saturated vapor pressure of bismuth selenide and telluride, Inorg. Mater., 5, (1969), 138-139. Cited on page 201. 

Measurements were made of the saturation vapor pressure of solid antimony and bismuth tellurides and of bismuth selenide. It was found that the evaporation of these compounds was of a dissociative nature, in accordance with the following equations... 

TABLE 2. Temperature Dependences of Total Vapor Pressures in Dissociative Evaporation of Antimony and Bismuth Chalcogenides... 

Our investigation shows that the vapor pressures of solid bismuth and antimony tellurides and of bismuth selenide are quite low. The working temperatures of thermoelements made of these substances do not exceed 700 C. Under such conditions, the evaporation of thermoelements should be of little significance, especially as the loss of matter from open surfaces occurs at a rate which is 6—65 times slower than the equilibrium rate of evaporation. The values of the evaporation coefficient (0.15-0.16) found in our study show that the evaporation process is fairly complex. This is supported by thermodynamic calculations, which demonstrate that the evaporation is of a dissociative nature. 

The dissociative evaporation of antimony telluride differs from the evaporation of bismuth selenide and telluride. The cause of this difference becomes obvious when we compare the molecular compositions of the metallic antimony and bismuth vapors. The principal component of the antimony vapor at temperatures and pressures corresponding to our measurements is... 

Sb4. Information on the composition of the bismuth vapor is less definite [5] but it is known that the principal component, under the conditions used in our study, is the monatomic bismuth. This is why the equilibrium in the dissociation of gaseous MeX is shifted in the direction of the formation of binary bismuth selenide and telluride, whereas the equilibrium in the case of SbTog is shifted in the direction of dissociation. Thermodynamic calculations confirming this assumption are presented in Table 4. These calculations are based on the data given in [1, 10, 12, 15]. The values of are calculated for the total pressures which correspond approximately to the values of the pressures obtained in our experiments at 800 C. 

Measurements were made of the vapor pressures of solid antimony and bismuth tellurides and of solid bismuth selenide. 

Hydro or solve thermal treatment often is a predominant route to prepare the Bi2MoOs photocatalyst. In a typical hydrothermal process, the temperature can be elevated above the boiling point of water, reaching the saturation vapor pressure. The temperature and filling rate of solvent in autoclave largely determine the internal pressure produced, which would have obvious effect on morphology and crystalline of obtained samples. Because of good reactivity between bismuth salt precursor and water molecule, a white precipitate is formed from hydrolysis of the bismuth... 

Bismuth is an ideal reductant for WCle because it is nontoxic, inexpensive, not impeded by a surface oxide, does notreaddy reduce WeClia, and forms volatile but low vapor pressure Bids for greatly improved safety in sealed tube reactions. Bismuth is also easily dispersed in reaction mixtures because it dissolves in molten BiClg. 

Among liquid metal candidates, mercury (Hg), sodium-potassium (NaK) alloy, sodium (Na), lead (Pb), and lead-bismuth eutectic (Pb-Bi) have been considered and used to build and operate liquid metal nuclear systems. However, liquid Na became the most smdied and used option mainly because it allowed, together with the selection of an appropriate fuel type (e.g., metal or oxide fuel), for a lower doubling time. On the other hand, hquid Hg was abandoned due to its toxicity, high vapor pressure and low boiling temperature as well as poor nuclear and heat transfer properties. More recently, in the framework of Generation IV, the development of fast reactors cooled with liquid metals considers hquid Na but also liquid Pb and liquid Pb-Bi as coolant... 

Solution properties. Little work has been done on determining physical properties of the solutions. The available results indicate that the. mall amount of dissolved material does not appreciably affect the phy. ical properties of density, viscosity, heat capacity, and vapor pressure. I or design purposes, the properties of pure bismuth can probably be used with. safety. 

The open end of the reaction tube is attached to an oil pump through a dust trap, and dry nitrogen is admitted at a rate such that the pressure is maintained at or below 25 mm. The bismuth(III) iodide is sublimed into the receiver end of the tube by heating with the spread burner flame and with an auxiliary Tirrill burner adjusted to maximum heat. Satisfactory progress of the sublimation is indicated by the persistence of yellowish-brown bis-muth(III) iodide vapors and by the absence of the violet color of iodine vapor. When the sublimation is complete, the tube is allowed to cool to room temperature in nitrogen at atmospheric pressure. The product is scraped from the receiver section of the tube and stored out of contact with the atmosphere. The yield is 72% based on bismuth. Anal. Calcd. for Bil3 Bi, 35.44. Found Bi, 35.42. The same result is found upon analysis of a resublimed sample of this product. 

The most abundant species in the equilibrium vapor over condensed metals are generally atoms as shown by Knudsen effusion mass spectrometry. The relative abundance of the homonuclear diatomic molecules was determined to be between 10 and 10 percent if they are detectable. Exceptions are bismuth and antimony. The dimer partial pressure over liquid bismuth at temperatures below 1000 K exceeds that of the monomer [83, 164, 165]. The tetramer is the most abundant species over liquid antimony [85]. Other polyatomic homonuclear species have so far been observed under equilibrium conditions for some of the alkali metals, as well as the group Ib, IVb, and Vb metals. Particularly large polymers up to 667 and Sn7 were detected for germanium [84,166,167] and tin [168],... 

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