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Vitreous amorphous form

A third monoclinic form, is obtained by heating the oxide in a sealed tube at 400° (the vitreous, amorphous form remains at the bottom of the tube) with the monoclinic form subliming onto the intermediate part of the tube at 200° (m 312"), and the octahedral form deposits at the top of the tube. The transition temperature between the last two forms is 250°. POISONOUS (particularly the vapour, handle in a ventilated fume cupboard). [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 600 19633]... [Pg.451]

A third monoclinic form, is obtained by heating the oxide in a sealed tube at 400° (the vitreous, amorphous form... [Pg.561]

Pure selenium, like sulfur, is allotropic, and exists in three forms a gray hexagonal form, a red monoclinic form, and a vitreous amorphous form. All forms can exist at room temperature and one atmosphere, but only the hexagonal form is thermodynamically stable [53]. [Pg.47]

The number of defects is maximal in the amorphous and liquid states. The phase diagram in Figure 5 shows the volume-temperature relationships of the liquid, the crystalline form, and the glass (vitreous state or amorphous form) [14], The energy-temperature and enthalpy-temperature relationships are qualitatively similar. [Pg.591]

Steel-gray crystalline brittle metal hexagonal crystal system atomic volume 13.09 cc/g atom three allotropes are known namely, the a-metaUic form, a black amorphous vitreous solid known as P-arsenic, and also a yellow aUotrope. A few other allotropes may also exist but are not confirmed. Sublimes at 613°C when heated at normal atmospheric pressure melts at 817°C at 28 atm density 5.72 g/cc (P-metallic form) and 4.70 g/cm (p-amor-phous form) hardness 3.5 Mohs electrical resistivity (ohm-cm at 20°C) 33.3xlCh (B—metallic polycrystalline form) and 107 (p—amorphous form) insoluble in water. [Pg.62]

Amorphous forms exhibit two colors, occurring as a red powder of density 4.26g/cm3 that has a hexagonal crystal structure and a black vitreous solid of density 4.28g/cm3. The red amorphous selenium converts to the black form on standing. Amorphous selenium melts at 60 to 80°C insoluble in water reacts with water at 50°C when freshly precipitated soluble in sulfuric acid, benzene and carbon disulfide. [Pg.812]

That arsenic may exist in both crystalline and amorphous forms was observed by Berzelius,2 who designated them a- and /3-arsenic, respectively. Two crystalline allotropes, metallic arsenic (the a-form) and yellow arsenic, are now recognised, and three amorphous forms, vitreous arsenic (the /3-form), grey and brown amorphous arsenic, have been described. The majority of investigators, however, deny the existence of more than one amorphous form, and indeed, as will be seen, it is an open question whether any amorphous form is to be considered as a true allotrope. [Pg.27]

Amorphous forms Vitreous, black selenium dark red-... [Pg.1337]

Silicate ceramics make the most of the versatility of silica (see section 1.5.2), which can exist in crystallized form (particularly quartz) or in amorphous form (silica glass) and, as a result, contain both crystallized phases and vitreous phases. [Pg.13]

Selenium exists in several allotropic forms. Three are generally recognized, but as many as that have been claimed. Selenium can be prepared with either an amorphous or crystalline structure. The color of amorphous selenium is either red, in powder form, or black, in vitreous form. Crystalline monoclinic selenium is a deep red crystalline hexagonal selenium, the most stable variety, is a metallic gray. [Pg.96]

Noncrystalline Silicas. The noncrystalline forms of silica iaclude bulk vitreous silica and a variety of other amorphous types, which are of substantial commercial importance (see SiLiCA, AMORPHOUS SILICA SiLiCA, VITREOUS SILICA). A review discussiag the occurrence, synthesis, properties, and apphcations of the various forms of silica adsorbents is available (71). [Pg.476]


See other pages where Vitreous amorphous form is mentioned: [Pg.1366]    [Pg.1366]    [Pg.358]    [Pg.253]    [Pg.326]    [Pg.469]    [Pg.469]    [Pg.592]    [Pg.83]    [Pg.326]    [Pg.469]    [Pg.469]    [Pg.290]    [Pg.28]    [Pg.30]    [Pg.31]    [Pg.128]    [Pg.134]    [Pg.1464]    [Pg.942]    [Pg.261]    [Pg.29]    [Pg.2]    [Pg.1114]    [Pg.424]    [Pg.450]    [Pg.351]    [Pg.335]    [Pg.458]    [Pg.760]    [Pg.340]    [Pg.433]    [Pg.314]    [Pg.69]    [Pg.471]    [Pg.497]    [Pg.525]    [Pg.190]    [Pg.539]   
See also in sourсe #XX -- [ Pg.1366 ]




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Amorphous form

Vitreous

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