Coloured earths

Among the former are certain white substances and particularly the coloured earths, which consist of earthy or clayey matter exhibiting definite colours owing to the presence of certain metallic compounds (especially of iron) and sometimes of free carbon. 

As regards impurities, coloured earths may contain extraneous substances naturally, while in artificial colours may be found substances derived from the raw materials or from the processes of manufacture, that is, with products which are only required technically, and not absolutely, pure. It is, however, essential that the impurities should not be harmful under the conditions in which the pigment is to be used. 

Feminine, from Hildesheimer, mud-coloured, with yellow ochre adhering to it. This species contains a hard, mud-coloured earth. 

From Vitriol, Gall, and Gum. Pliny (1.35. c. 6.) gives other methods — as from Sulphur-coloured Earth, from Coals, Soot, etc. 

Native, found abundantly, cleaving to hard, ash-coloured earth. 

TERRA FERE LUTEA — Slimy Earth TERRA SIGILLATA — Red-coloured Earth. 

II expresses his belief in alchemy and contains absurd statements which injured his reputation. He regarded metals as composed of phosphorus, a colouring earth, a talc-like earth, and a salt in gold, mercury, platinum, and iron, the colouring earth is cobalt in copper it is a red earth. Fanciful compositions of salts are given. A second part of II which was to contain expen-mental proofs, never appeared, but III took its place. 

Wads are dark brown to black-coloured earths containing c. 50% manganese oxides. 

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

The structural complexity of the 3D framework aluminosilicates precludes a detailed treatment here, but many of the minerals are of paramount importance. The group includes the feldspars (which are the most abundant of all minerals, and comprise 60% of the earth s crust), the zeolites (which find major applications as molecular sieves, desiccants, ion exchangers and water softeners), and the ultramarines which, as their name implies, often have an intense blue colour. All are constructed from Si04 units in which each O atom is shared by 2 tetrahedra (as in the various forms of Si02 itself), but up to one-half of the Si... 

Chromium, 122 ppm of the earth s crustal rocks, is comparable in abundance with vanadium (136 ppm) and chlorine (126 ppm), but molybdenum and tungsten (both 1.2 ppm) are much rarer (cf. Ho 1.4 ppm, Tb 1.2 ppm), and the concentration in their ores is low. The only ore of chromium of any commercial importance is chromite, FeCr204, which is produced principally in southern Africa (where 96% of the known reserves are located), the former Soviet Union and the Philippines. Other less plentiful sources are crocoite, PbCr04, and chrome ochre, Cr203, while the gemstones emerald and ruby owe their colours to traces of chromium (pp. 107, 242). 

The most satisfactory test for caramel is to shake with Fuller s earth, as recommended - by Crampton and Simons. If the colour is due to caramel and a grade of I uller s earth is used, which experience has proved suitable, the solution, after filtering, is yellow or colourless. This test does not positively identify the colour, as some other brown substances may give similar reactions, but no such substance is liable to be present in vanilla extract. 

You could visit earth, hire a mechanical workshop in a remote area, car-jack a few specimens, and dissect them. You would observe that cars differ in their colour, shape, size and spec. Some may even contain a bar, cinema or swimming pool, but, perhaps, limousines are excluded from your exploration. On closer examination you would notice small ID-numbers imprinted on various strategic body parts. In short - you would find no two cars that are exactly the same. 

Procedure 10% aqueous solution of potassium iodide, KI, when exposed to sunlight, liberated I2 due to the photolytic decomposition and gave blue colour with freshly prepared starch solution. The intensity of blue coloured complex with the starch increased many fold when the same solution was kept in the ultrasonic cleaning bath. As an extension of the experiment, the photochemical decomposition of KI could be seen to be increasing in the presence of a photocatalyst, Ti02, showing an additive effect of sonication and photocatalysis (sono-photocatalysis) However, the addition of different rare earth ions affect the process differently due to the different number of electrons in their valence shells. 

One parameter which has so far been neglected in the discussion of the influence of physical conditions on the young Earth is the pressure in rock layers. This has been the subject of investigation by Ohara and co-workers from the Tohoku University in Sendai, Japan, who studied the pressure-dependence of the polymerisation of dry glycine at 423 K and pressures from 5 to 100 MPa. The experiments took between 1 and 32 days. Depending on the pressure, light to dark yellow products were obtained. At low pressures, the colour is probably due to the presence of melanoids. 

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