Pigment removal

Transgenic plants"1 0.1-0.3 10-15 Protein extraction lipid and pigments removal Very low cost heavy pretreatments... 

Pigment components have also been identified from their IR spectra. Figure 6 shows the spectrum obtained from a purple pigment removed from... 

Flesh-colored and red pigments removed from MS 232 (Greek gospel book) have spectral features similar to those in Figures 7 and 8. This similarity suggests that cochineal was also used as the red pigment in this manuscript. 

Another example of pigment identification by IR microspectroscopy is shown in Figure 10. The bottom spectrum was obtained from a blue pigment from MS 972 (Archaic Mark) the top spectrum is a reference spectrum of Prussian blue. The band corresponding to the C=N of ferric ferrocyanide is common to both spectra. Replicate spectra of blue pigments removed from different locations in MS 972 indicate that the average frequency of this band is 2083 6 cm"1. The ubiquitousness of an iron blue in this manuscript raises doubts about the authenticity of this manuscript. 

Pigment components have also been identified from their IR spectra. The infrared spectrum obtained from a purple pigment removed from MS 965 showed bands due to ultramarine blue and white lead. A red pigment (cochineal ) must also be present with the blue to produce the purple colour. 

Uric Acid may accompany urates in very acid urine. Acidify 10 ml. urine with a few drops of strong Hd, and set aside for about twenty-four hours. The mic acid is precipitated as a few dark crystals, heavily pigmented. Remove by pipette and identify microscopically. 

The examples in the preceding section, of the flotation of lead and copper ores by xanthates, was one in which chemical forces predominated in the adsorption of the collector. Flotation processes have been applied to a number of other minerals that are either ionic in type, such as potassium chloride, or are insoluble oxides such as quartz and iron oxide, or ink pigments [needed to be removed in waste paper processing [92]]. In the case of quartz, surfactants such as alkyl amines are used, and the situation is complicated by micelle formation (see next section), which can also occur in the adsorbed layer [93, 94]. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Green coloration, present in many vegetable oils, poses a particular problem in oil extracted from immature or damaged soybeans. Chlorophyll is the compound responsible for this defect. StmcturaHy, chlorophyll is composed of a porphyrin ring system, in which magnesium is the central metal atom, and a phytol side chain which imparts a hydrophobic character to the stmcture. Conventional bleaching clays are not as effective for removal of chlorophylls as for red pigments, and specialized acid-activated adsorbents or carbon are required. 

Cmde oils from these processes are often of insufficient quaUty to be used directly, particularly for edible products. Impurities such as pigments, phosphatides, volatile odorous compounds, and certain metals must be removed by further processing. 

Examination. Microscopic examination (123) can identify the fibers present ia the pulp (124). Inks, watercolor pigments and media, etc, are analyzed similarly to the pigments and media for paintings. However, sample removal tends to be far more disfigutiag and hence constitutes an even more restrictive factor. Watermarks are studied with the aid of beta-radiography. Examination ia iafrared illumination can assist ia the reading of documents of which the ink has faded. 

Pigment used for dry blending is dried overnight at 150°C in a vacuum oven to remove absorbed gases and moisture. It is screened through a 149-p.m (100-mesh) screen directly onto the cubes, which are roUed or tumbled for at least 15 min. The pigmented resin is stored in an airtight container to prevent absorption of moisture. 

Solvent extraction removes chlorophyll and other pigments to give a light-colored product but increases processing costs. Furthermore, solvent extraction removes p-carotene and reduces vitamin A activity (89) (see Terpenoids Vitamins). Supercritical CO2 extraction at 30 and 70 MPa (4,350 and 10,150 psi) and 40°C removed 90 and 70% carotene and lutein, respectively, from alfalfa LPC (96). This process avoids organic solvent residues and recovers valuable by-products. 

Melanin Drying. One development (ca 1993) in hair coloring involves the formation of pigments within the hair that are very similar to natural melanin. Thus either catalytic or air oxidation of 5,6-dihydroxyindole [3131-52-0] can be effectively used to permanently dye hair within a short time (38). The formed color can, if required, be further modulated with dilute H2O2 or can be even totally removed from hair by this oxidant. 

Laser removal of tattoos and of colored birthmarks has been widely studied. A high power pulsed laser at a wavelength absorbed by the pigment is used to vaporize the pigment and to bleach the colored area. Ruby, Nd YAG, and dye lasers are favored for this purpose. 

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