Spar, iceland

Iceland spar, see Calcium carbonate lodyrite, see Silver iodide... 

Fig. 5.5 Adsorption isotherms of butane at 0°C on Iceland Spar ground for 1000 h. Curve (i), the solid was outgassed at 25°C. Curve (ii), the solid was outgassed at 1S0°C. O, adsorption p Q, desorption.

Ice cream imitation Iceland spar Ice milk Ice removal... 

Iceland spar s the purest limestone, virtually pure calcite of about 99.9% CaCO. It is also known as optical calcite its occurrence is rate. 

Doppelspat, m. Iceland spar, doppelatark, a. double-strength. 

IslMnder Doppelspat. Iceland spar, ifilflndisch, a. Iceland, Icelandic. — islMndischer Doppelspat, Iceland spar. 

In the theory of optics this phenomenon is accounted for in terms of geometrical construction, but the physical picture is less convincing. Double refraction is a well-documented property of most crystals, at its most spectacular in Iceland spar. The double image of an object viewed through the crystal indicates the existence of two independent rays and not the components of a single ray. In mathematical terms the two rays are linearly independent and therefore orthogonal. Any intermediate situation represents a linear combination of the two orthogonal basis vectors and can be resolved into two components. What happens to an individual photon is however, not clear. 

Iceland spar, 75 28 ICI deep shaft wastewater treatment process, 7 744... 

Compton RG, Daly PJ, House WA. The dissolution of Iceland spar crystals the effect of surface morphology. J Colloid Interface Sci 1986 113 12-20. 

White pieces in the form of Iceland spar crystals. 

Unlike the octahedral form, vitreous white arsenic on heating melts before volatilisation begins.8 The density of the glass has been variously given 9 as 3-70 to 3-88 Winkler found the density under water to be 3-7165 at 12-5° C. but under petroleum 4-6815. The glass is brittle and its hardness is comparable with that of Iceland spar.10... 

Calcite is perhaps best known because of its power lo produce strong double refraction of light such that objects viewed through a clear piece of calcite appear doubled in all of their parts. A beautifully transparent variety used for optical purposes comes from Iceland, for ihat reason is called Iceland spar... 

Edmond Becquerel (1820-1891) was the nineteenth-century scientist who studied the phosphorescence phenomenon most intensely. Continuing Stokes s research, he determined the excitation and emission spectra of diverse phosphors, determined the influence of temperature and other parameters, and measured the time between excitation and emission of phosphorescence and the duration time of this same phenomenon. For this purpose he constructed in 1858 the first phosphoroscope, with which he was capable of measuring lifetimes as short as 10-4 s. It was known that lifetimes considerably varied from one compound to the other, and he demonstrated in this sense that the phosphorescence of Iceland spar stayed visible for some seconds after irradiation, while that of the potassium platinum cyanide ended after 3.10 4 s. In 1861 Becquerel established an exponential law for the decay of phosphorescence, and postulated two different types of decay kinetics, i.e., exponential and hyperbolic, attributing them to monomolecular or bimolecular decay mechanisms. Becquerel criticized the use of the term fluorescence, a term introduced by Stokes, instead of employing the term phosphorescence, already assigned for this use [17, 19, 20], His son, Henri Becquerel (1852-1908), is assigned a special position in history because of his accidental discovery of radioactivity in 1896, when studying the luminescence of some uranium salts [17]. 

Figure 1. Spectra of non-biogenic calcite (Iceland spar) and liquid H2O. Calcite spectrum offset vertically by 0.2.

The wave lengths of X-rays are too small to be measured in the same way as ordinary light waves. They have been measured by means of crystals. The atoms in a crystal like Iceland Spar or Diamond are arranged in regular layers at equal distances apart, as shown in Fig. 14. 

This can be prepared in several different ways. Commonly dry Castile soap is dissolved in 80 per cent, alcohol in such proportions as will yield a solution well above the desired final concentration 100 grams per litre is a convenient ratio. After allowing this solution to stand at rest for several days for the deposition of undissolved matter, a quantity of the clear liquid is withdrawn (usually 75-100 c.c. per litre of final solution), and so diluted with 80 per cent, alcohol as to produce a solution which on titration with a known weight of calcium chloride solution under the standard conditions will give results in accordance with Clark s table. The calcium chloride solution is best prepared by dissolving 0-2 grams of Iceland spar in dilute hydrochloric acid excess of acid is removed by evaporation on a water bath and the solution then diluted to 1 litre with distilled water. A mixture of 25 c.c. of this solution, mixed with 25 c.c. of water, should require 7-8 e.e. of Clark s standard solution for the production of a permanent lather. 

Some of the Group IA and IIA metals are found in nature in the form of carbonates, silicates, nitrates, and phosphates. For example, calcium carbonate is one of the most important naturally occurring compounds, and it is found in several forms. The most common form of calcium carbonate is limestone, which is used extensively as a building stone as well as the source of lime. Other forms include chalk, calcite, aragonite, Iceland spar, marble, and onyx. Many other materials such as egg shells, coral, pearls, and seashells are composed predominantly of calcium carbonate. Thus, it is one of the most widely occurring compounds in nature. 

The second example is for the precipitation of calcium carbonate from Ca(HC03)2 solutions. The mechanistic model was derived by Plummer et al. [40] from a kinetic study of the dissolution of Iceland spar crystals. The approach has more recently been extended to the interpretation of crystal growth [41]. The model is based upon the reaction between a partially dehydrated [Ca-HC03]+ complex or ion-pair and possible anionic reaction... 

Equation (135) has been applied to the crystal growth of Iceland spar with the rate constant k3 determined from dissolution experiments [40, 43]. Plummer et al. [40] found that the dissolution rate could be described by an equation of the form... 

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