Red ochre

Ferric oxide 41S4 Fe203 Brown red colcofhar crocus hematite Indian red iron oxide Won oeroxide jeweler s red red bole red ochre red oxide of iron rouge sesquioxtde of iron soecutar iron ore Venetian red. 

Slip coatings, ochre red and black decoration, impressed designs, by about rouletting, incised decoration, control of oxidation-reduction during firing... 

When dry colouring matters, as vermilion, yellow-ochre, red-lead, and various metallic oxides have to he mixed with the melted soap care must be taken not to allow the paste to become too stif otherwise, when these are incorporated with the mass, it may become unmanageable. 

Silver chromate(Vl), with composition Ag2Cr04, is hsted by the Colour Index (1971 Cl 77825) as a purple pigment precipitated from a nuxture of silver nitrate and potassium chromate, and used as an artists colour under the name of purple red (. v.). It is described by Riffault et al. (1874) as a purple-red pigment, and is mentioned by other late nineteendi century documentary sources such as Scott Taylor (1885) and Salter (1869), the latter of whom describes silver red as being made from silver nitrate and monochromate of potash to give a fine ochre-red colour. 

Iron oxides and hydroxides gronp Hematite Limonite Ochre Red ochre, Venetian red. Yellow ochre Church (1901) 179... 

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. 

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... 

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. 

Naturally occurring iron oxide pigments are widely distributed geographically and can be found in a wide range of colours from black to reds and yellows, depending on composition and crystal structure. Ochres of many kinds and from different sources were often used in oil... 

Erlandson, J. M., Robertson, J. D., and Descantes, C. (1999). Geochemical analysis of eight red ochres from western North America. American Antiquity 64 517-526. 

Diffusion (A). Lipophilic substances (red dots) may enter the membrane from the extracellular space (area shown in ochre), accumulate in the membrane, and exit into the cytosol (blue area). Direction and speed of permeation depend on the relative concentrations in the fluid phases and the membrane. The steeper the gradient (concentration difference), the more drug will be diffusing per unit of time (Pick s Law). The lipid membrane represents an almost insurmountable obstacle for hydrophilic substances (blue triangles). 

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