Ochre

Sulphuric Acid.—This is also determined in an aliquot part of the filtrate from the precipitation of the iron and alumina, by acidifying with hydrochloric acid and precipitating with barium chloride in the ordinary way. 

Copper.—In an aliquot part of the hydrochloric acid solution obtained in determination No. 2 (above) the ferric salts are reduced by means of sodium hypophosphite and the copper then precipitated with hydrogen sulphide, the precipitate being dissolved in nitric acid and the copper then determined electrolytically. 

Resistance towards Acids.—1 gram of the material is digested with a litre of 1% sulphuric acid with occasional shaking, a few c.c. of the clear liquid being withdrawn every 24 hours and the dissolved iron determined. 

True English red should contain only small quantities of impurities (usually not more than 1-2% of substances insoluble in acids) and should consist essen tially of ferric oxide it should not contain copper or free sulphuric add. Products containing barium sulphate or chalk or gypsum in other than very small quantities are to be regarded as intentional mixtures as much as 80% of gypsum is found in some commercial samples. 

Iron minium contains larger amounts of silica and silicates it may contain 50-90% of ferric oxide, good qualities containing at least 80% it should not contain added extraneous substances. 

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Naturally occurring colored minerals that contain oxides of iron are known by such names as ochre [1309-37-1], umber [12713-03-0], sienna [1309-37-1], etc. These show greater variation in color and tinting power than the synthetic equivalents, and the nature and amount of impurities in the national products is also variable. Most of the pigments identified in Table 9 are, therefore, manufactured synthetically. They are primarily used in skin-makeup products and in eye-area colorants. 

A frequently cited example of protection from atmospheric corrosion is the Eiffel Tower. The narrow and, for that age, thin sections required a good priming of red lead for protection against corrosion. The top coat was linseed oil with white lead, and later coatings of ochre, iron oxide, and micaceous iron oxide were added. Since its constmction the coating has been renewed several times [29]. Modern atmospheric corrosion protection uses quick-drying nitrocellulose, synthetic resins, and reaction resins (two-component mixes). The chemist Leo Baekeland discovered the synthetic material named after him, Bakelite, in 1907. Three years later the first synthetic resin (phenol formaldehyde) proved itself in a protective paint. A new materials era had dawned. 

Note Aldoses other than glucose can also be used e.g. arabinose [1], xylose [2, 3, 7] or ribose [4]. The background color is least on cellulose layers when cellulose acetate, aluminium oxide 150, silica gel, RP, NH2 or polyamide layers are employed the background is a more or less intense ochre. The detection limit of carboxylic acids on cellulose layers is ca. 0.5 pg substance per chromatogram zone. 

Proline yellow yellow brown yellow ochre... 

Red-violet chromatogram zones on a weakly ochre-colored background are yielded within a few seconds (< 30 s) on silica gel layers. 

Substances containing aldehyde or keto groups yield yellow to orange-yellow chromatogram zones on an almost colorless background [1,11]. Silymarin appears red-blue and silydianine ochre-colored [9]. 

Colored zones are formed (tin violet-red to blue) on a yellow ochre background... 

Detection and result The chromatogram was freed from mobile phase (heated to 110°C for 30 min) and then exposed to bromine vapor for 1 h in a chamber, after blowing off excess bromine from the layer it was immersed for 1 s in the reagent solution. On drying in air dibutyltin dilaurate hRf 25 — 30), dibutyltin dichloride (kR( 25 — 30), dioctyltin oxide (hR( 40), tributyltin oxide (hRf 80), tributyltin chloride (hRf 80) and tetrabutyltin (hRf 85-90) produced persistent blue zones on a yellow ochre background (Fig. 1). 

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). 

Pipework should be easily identifiable in accordance with BS 1719. Where the normal pressure in the pipe exceeds 75mbar, consideration should be given to labeling the pipe with the normal operating pressure. In buildings in which there are no other piped flammable gas supplies it is sufficient to paint the pipe yellow ochre or to band it with appropriately colored adhesive tape. In large complex installations, it is desirable to identify pipe contents more precisely, and in those instances, the base color should be supplemented with a secondary code band of yellow and/or its name or chemical symbol. 

Some pigments promote corrosion owing to their content of soluble salts, their reactivity, or their electrochemical action, and thus should be avoided. Rust of the spotted type can be the consequence of their presence in a paint, especially the hrst coat, e.g. of graphite (noble to steel), some red oxides of iron, gypsum, ochre or lamp black. 

Mataziette. Swiss Dynamite invented about 1877 contg NG 40% plus sand, ochre, powd coal and resinous materials (Ref 1). Ref 2 describes it as a mixt of NG, sand and chalk Refs 1) Daniel (1902), 419 2) CondChem-... 

Selenazolo[3.2-a]pyrimidinium salts (Scheme 53) can be obtained by condensation of 2-amino-4-phenylselenazoles with an excess of /3-diketone of the type. R OCHR-COR,. 

On a beige-yellow background 2-aminophenol (h/ f 55-60) appeared as ochre brown, 4-aminophenol (h/ f 40-45) as violet-brown and 4-aminosalicylic add (h/ f 20-25) as pale brown-violet chromatogram zones. 

On a dark background cholesterol (Eluent A, h/ f 20-25) emitted blue, coprostanol (Eluent A, h/ f 25-30) blue, 4-cholesten-3-one (Eluent A, h/ f 40-45) blue, 5a-cholestan-3-one (Eluent A, h/ f 60) blue, coprostanone (Eluent A, h/ f 70) blue, estriol 3-sulfate (Eluent B, h/ f 5-10) yellow, 11-ketoetiocholanolone (Eluent B, h/ f 15-20) blue, estrone (Eluent B, h/ f 20-25) ochre, 11-desoxycorticosterone (Eluent B, h/ f 30-35) yellow, 17a-ethinyl-5-androstene-3p,17p-diol (Eluent B, hRj 45-50) ochre, 4-cholesten-3-one (Eluent B, h/ f 55-60) faint blue and coprostanone (Eluent B, h/ f 65-70) violet fluorescences. 

Weakly fluorescent zones were visible under long-wavelength UV light (X = 365 i (Fig. 1). Cortisone (h/ f 0-5), dienestrol (h/ f 10-15), 4-androstene-3,17-dione (It 50-55) and 4-cholesten-3-one (h/ f 60-65) had an ochre fluorescence. Diethylsti estrol (h/ f 10-15), 17a-ethinyl-l,3,5-estratriene-3,17B-diol (h/ f 25-30) and estro (h/ f 35-40) had a blue emission. 

Phloroglucinol (h/ f 15-20) yielded an ochre-colored and pyrogallol (hRf 35-40) a brown chromatogram zone on a colorless background. The detection limits were 20 ng substance per chromatogram zone. 

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