Potash mica

Eali-glas, n. potash glass, -glimmer, m. potash mica, muscovite. kalUuLltig, a. containing potash. 

This is the formula of potash mica or muscovite, the arrangement of atoms in the structure being similar to that of pyrophyllite, except that there are K ions between the silica layers (Figure 15). 

In exactly the same way, from the unit formula of potash mica we find that 1 part by weight of KgO corresponds to 8.46 parts by weight of potash mica. Hence from Table 6 the percentage of potash mica in this clay is 2.80x8.47=23.72%. 

In the next step of the calculation, we must remember that the alumina (29.30% from Table 6) is combined in three minerals— kaolinite, soda mica, and potash mica. Knowing now the percentage soda and potash micas, we can calculate from their formulae how much AI2O3 they contain. Subtracting this amount from the total AlgOg (29.30%), we can find how much AlgOg is present as kaolinite, and hence calculate the percentage of kaolinite. 

Similarly, the percentage of AI2O3 in potash mica is 38.40%, and the percentage of AI2O3 combined in potash mica in the clay= 23.72x0.3840=9.11%. Hence the total AI2O3 combined in the form of micas =0.59+9.11 =9.70%. 

Similarly, silica combined as potash mica =23.72x0.452=10.72%. 

Although the results in Table 8 are given to the first decimal place, it is doubtful whether the method warrants such accuracy, for the errors arise, not in the calculation, but in the assumptions that are made. For example, the composition of potash mica does not always correspond exactly to the ideal formula, KAl3Si30io(OH)2, and therefore the conversion factor of Table 7 may differ slightly from the stated value. The same thing applies to other minerals. Furthermore, the clay may contain silicate minerals other than kaolinite, micas and quartz this would render the method of calculation unsound. In cases of doubt, however, the composition should be checked by thermal analysis. X-ray analysis, or both. 

The conventional ceramics, brick, earthenware, and porcelains, are made from clay. Clay is a complex material, but its main component is a mineral called kaolinite. Pure kaolinite is a nice white powdery mineral. Such white clay is called China clay. Clay is often colored though, because it contains small quantities of colored material such as iron oxide (Fe Oj) that gives a brownish color. Other iron compounds present give grayish colors. All iron compounds turn into iron oxide (Fe Oj) when fired, and hence the earthenware made from grayish clay usually ends up with a brownish color. Ordinary clays contain in addition other minerals such as quartz, soda mica (paragonite), and potash mica (muscovite). 

Potassium is found in feldspars and micas, and is the fourth most abundant cation in seawater (390 mg kg-1). Potassium compounds are usually obtained from evaporites (i.e., residues from evaporated water) as KC1 ( potash ) or carnallite, mainly for use in fertilizers. 

A powder which burns with a green flame is obtained by the addition of nitrate of baryta to chlorate of potash, nitrate of potash, acetate of copper. A white flame is made by the addition of sulfide of antimony, sulfide of arsenic, camphor. Red by the mixture of lampblack, coal, bone ash, mineral oxide of iron, nitrate of strontia, pumice stone, mica, oxide of cobalt. Blue with ivory, bismuth, alum, zinc, copper sulfate purified of its sea water [sic]. Yellow by amber, carbonate of soda, sulfate of soda, cinnabar. It is necessary in order to make the colors come out well to animate the combustion by adding chlorate of potash.15... 

Mica, biotite, potash, feldspars, silimanite, zircon, graphite, iron carbide, lead sulfate... 

Although compounds of sodium and potassium were known in ancient times, it was not until Humphrey Davy s famous electrolytic experiments in 1807 on molten caustic soda and potash that the metals themselves were first isolated. Lithium was first recognized as an alkali metal in various silicate and mica minerals in 1817 (by ArfVedson, who thus named it from the Greek word for stone) and first isolated, again by Davy, in 1818. The discovery of cesium (1860) and rubidium (1861) had to await the development of atomic spectroscopy (by Bunsen and Kirchoff) their names reflect the colors of their dominant spectral lines (Latin caesius, sky blue, and rubidus, deep-red). 

Oxids.—Lead Monoxid—Protoxid—Hassicot—Litharge —Plum-bi oxidum (XT. S. Br.)—PbO—222.9—is prepared by heating Pb, or its carbonate, or nitrate, in air. If the product have been fused, it is litharge if not, massicot. It forms copper-colored, mica-like plates, or a yellow powder or crystallizes, from its solution in soda or potash, in white, rhombic dodecahedra, or in rose-colored cubes. It fuses near a red heat, and volatilizes at a Avhite heat sp. gr. 9.277-9.5. It is sparingly soluble in HaO, forming an alkaline solution. 

Lithia is not quite so soluble in water as soda or potash, nor is it so caustic but it very much resembles these alkalies. Its solution attracts carbonic acid as readily as theirs from the atmosphere. When lithia is fused on platinum, it corrodes and stains the metal. Lithia and all its salts give a blood-red colour to flame. The carbonate of lithia is sparingly soluble, and its phosphate is nearly insoluble. Lithia occurs too rarely to admit of any useful application / but it is important to know that lithion-mica, which is recognised by its easy fusibility before the blow pipe, and by its tinging the outer flame red, has hitherto been only found associated with albite and topaz, or pycnite, in tin districts, and its occurrence, thus associated, may be looked on as a sure indication of the existence of tin in the locality. 

There exists a group of minerals that is structurally similar to the micas, but contain less potash and more combined water than the latter. These materials are called illites, but have also been called hydrous micas or sericites. 

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