Ochre brown

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. 

Iron oxides (sienna and ochre) brown Fe203 H20, clay, etc. 

Proline yellow yellow brown yellow ochre... 

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. 

Also called 2,6-Dinitro-4-Picrylaminephenol in Ger). (O, N)3C6H2NHC6H2(N02)20H mw 410.22, N 20.49%, OB to C02 -62.4% ochre-yel crystals (from HAc), mp 248° insol in water, si sol in ale sol in alkalis with formation of a deep-brown color. Prepd by heating picryl chloride, isopicraminic acid NaAc in aq ale. No explosive props are mentioned for it nor for the tetranitro derivatives (Ref 2). The Na salt, of the pentanitro derivative NaCi2HsOuN6, red platelets, explodes above 300°. The 3 -Hydroxy-4-methyl-pentanitro diphenylamine is not explosive (Ref 3)... 

A total of 65 ochre samples recovered from a range of excavated contexts at Jiskairumoko were analyzed by INAA (Table II). Ochre samples were recovered as both singular lumps and powdered material. Only ochre masses were analyzed to prevent any possible contamination issues. Samples ranged in color from yellow to dark brown, with varying shades of red and red-brown in between. These color variations may indicate differing iron concentrations or particle sizes, and may be due to inherent impurities in the mineral (47) or heat treatment. Table II lists the examined samples with Munsell values. 

An artificial pigment analogous to the ochres is Mars yellow, consisting of a mixture of hydrated ferric oxide with calcium sulphate, alumina or zinc oxide of analogous composition are the pigments derived from it by more or less pronounced heating (Mars orange, red, brown, violet, purple). 

The composition of ochres is very variable -. the content of ferric oxide anti its degree of hydration, on which the quality and intensity of the colour depend, may vary widely. The colour may be changed to brown (brown ochres) by oxides of manganese. A good ochre should not contain carbonates or sulphates and should not be adulterated with chalk, gypsum or barium sulphate or " improved with other colours. Ochres containing arsenic should not be used, especially for internal walls or wall-papers. 

The most common of these pigments are certain earths, such as Sienna or Italian earth—which is a brown ochre—umber, Cologne earth or Cassel brown blacks with a carbon basis graphite, consisting of more or less impure crystalline carbon. 

This is a species of earthy peat, ground and suitably punnett tt- consists principally of humous and carbonaceous matter. It forms a light, brown powder, which, when heated in the air, burns with moderate ease, giving no flame and emitting a bituminous odour. It may be mixed with ochre, umber and ferric oxide, such mixtures (prepared Cologne earth) being sold under various names. 

The reaction products of interest to us in this respect are the salts of hydrogen cyanide, called cyanides,314 in particular, the iron cyanide group, formed by a compound of iron and cyanide. Iron occurs universally in nature. It is iron which gives brick its red color, sand its ochre color, and clay its color ranging from yellowish to reddish-brown. More precisely, we are speaking of iron oxide, popularly known as rust . Basically, all walls consist of at least 1% rust, as a result of sand, gravel, clay, and cement, of which the wall is constructed. 

Mixtures for Matches, For sulphur dips Phosphorus, 3 parts glue, 5 parts sand, 1 part incorporated below 100° Fahr., with 10 parts of water. Or, phosphorus, 5 parts fine sand, 4 parts red ochre, 1 part (or, ultramarine), part gum-arabic, 5 parts, in 6 pints of water (or, 4 parts of glue in 9 parts of water). For etearine dips Phosphorus, 3 parts brown oxide of lead, 2 parts turpentine, i part, softened in 3 parts water. Instead of the brown oxide, 2 parts of red lead stirred up with i part of nitno acid mar bo used. 

As with iodine, starch forms an inclusion complex with bromine vapor.205 Depending on the starch variety, different colors are developed by the complex. Maize and wheat produce an ochre color, rice produces a light-buff color, potato and sago develop a pale-yellow color, and cassava forms a cream color.69 Iodine cyanide (and bromine)-amylose complexes are brown-black and dark brown, respectively.206 The adsorption of chlorine and iodine proceeds according to the Freundlich isotherm. A discontinuity on the Freundlich isotherm plot is reported, which possibly results from the swelling of starch granules454... 

In the pure condition auric hydroxide resembles ferric hydroxide in appearance, and has the colour of brown ochre, but impurities impart to it a yellowish or greenish tint. It is soluble in nitric acid and hydrochloric acid, and in hot potassium-hydroxide solution, but insoluble in solutions of the carbonates of the alkali-metals and ammonium.6 It dissolves in solutions of the chlorides of sodium, potassium, and barium with production of complex salts.7 Prolonged heating at 140° to ISO0 C. eliminates all its water, with formation of auric oxide, Au2Oa. At 155° to 165° C. auric oxide is converted into gold monoxide, AuO.8... 

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