Barium fluorite

Bands. See Energy bands Barium, values of properties. See Simple metals Barium fluorite. See Fluorites Barium titanate, 450, 466f Beryllium molecule, 28... 

As shown in Ikble 20-2, lithium chloride humidity sensors have rather slow responses to humidity compared to other types of humidity sensors. This type of humitidy sensor cannot, therefore, be used in automatic control systems which require a rapid response. They are, however, widely used for meteorological observations such as radiosonde because of their reproducibility, long term stability, and low cost [7]. Care should be taken when using this type of sensor in very humid environments because the accuracy and lifetime are lowered. Thin films of potassium metaphosphate [9] and barium fluorite [10] are also used as humidity sensors. The film of potassium metaphosphate is deposited on a glass substrate by vacuum sublimation and Ag paste is used as the electrodes. Such sensors show a response to humidity within 2 s, but are not stable [9]. 

Goldschmidt predicted from his empirical rule that calcium chloride would not have the fluorite structure, and he states that on investigation he has actually found it not to crystallize in the cubic system. Our theoretical deduction of the transition radius ratio allows us to predict that of the halides of magnesium, calcium, strontium and barium only calcium fluoride, strontium fluoride and chloride, and barium fluoride, chloride,... 

For flotation of barite, sodium silicate was used as a depressant and barium chlorite as a barite activator. Barite collector SR82 was composed of petroleum sulphonate, sodium alkyl sulphate and succinamate mixture. The collector was selective towards both fluorite and bastnaesite. Over 96% of the barite was recovered in a relatively high-grade concentrate. 

In 1768 A. S. Marggraf made the first chemical investigation of fluorite, distinguished it from heavy spar and selenitic spar (sulfates of barium and calcium), and showed that it is not a sulfate (77, 78). When he distilled pulverized fluorspar with sulfuric acid from a glass retort, the glass was badly attacked and even perforated. He noticed that an earth [silica] appeared in the receiver, and therefore concluded that the sulfuric acid had liberated a volatile earth from the fluorspar (77). 

BARYTOCALCITE. This mineral is a carbonate of barium and calcium il crystallizes in the monoclinic system but occurs massive as well. Il lias a perfect cleavage parallel to the prism and one, less perfect, parallel to the base fracture, sub-conchoidal brittle hardness, 4 specific gravity, 3.66-3.71 luster, vitreous color, white or gray or may be greenish or yellowish transparent to translucent. Barytocalcite is found in Cumberland. England, associated with barite and fluorite. 

We first look at the fluorides of barium. Only BaF2 is known, a typically ionic solid having the fluorite (8 4) structure. From Table 5.2, we see that the calculated lattice energy is very close to the experimental value in other words, we can calculate the enthalpy of formation of BaF2(s) almost within the limits of experimental uncertainty. Why have BaF3 and BaF not been prepared Presumably they are thermodynamically unstable with respect to other species. In order to verify this supposition, let us estimate the enthalpies of formation AHf of BaF(s) and BaF3(s), assuming these to be ionic. 

Barium sulfate, BaS04, occurs in the mineral barite (a). Calcium fluoride, Cap2, occurs in the mineral fluorite (b). Both are clear, colorless crystals. Minerals are often discolored by impurities. 

In 1787 a new mineral, strontianite, was found in a lead mine near the village of Strontian in Scotland. Some mineralogists classified it as a variety of fluorite (CaFj). The majority of scientists, however, believed that strontianite was a variety of witherite (barium mineral BaCOg). 

Non-glass membranes were introduced in 1935 36 by Tendeloo (, ) who made measurements with slices of barium sulphate and calcium fluoride (fluorite). This was followed in 1937 by the use of pressed silver chloride polycrystals on platinum discs by Kolthoff and Sanders (5). Twenty years later, Tendeloo and co-workers ( 9) went on to describe membranes of calcium salts of low water solubility in low melting point paraffin. 

Calcite. Quartz. Barium oxide Zinc oxide.. Cupric oxide Lead sulfide. Fluorite.. . . ... 

Barium group Barium sulfate Calcite Fluorite Galena Sphalerite Witherite Bamtine Baryta Blanc fixe Bolognian spar, Cauk, Ceruse de Venise Heavy spar Lapis bononiensis Lapis Solaris Satin white Schwerspath Spath pesant Tyrol white... 

The difluorides of strontium, barium, cadmium and mercury all adopt the fluorite crystal stmcture. The difluorides of magnesium and zinc adopt a mtile -type stmcture where each metal cation is surrounded by six F anions at the comers of an octahedron, and each anion is surrounded by three metal caritnis in a planar trigonal arrangement [19]. 

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