Pigments considerations

The retention values demonstrated that the separation of anka pigments considerably depends on the composition of the mobile phase, furthermore, it was found that the TLC... 

An elegant publication from Aman and Thoma [84] outlined the various options open to the stabilisation of photolabile oral products. The addition of lightabsorbing agents is a well-established approach to stabilising photolabile products [85]. Aman and Thoma [84] reported that the incorporation of light-absorbers and pigments considerably improved the photostability of the very light sensitive... 

Ordinary xanthophyll absorbs in a region quite close to the Soret band (400 nm). Stacking moves the absorption closer to 500 nm. Other xanthophylls and carotenoids also absorb in the upper visible region. Thus, the accessory carotenoid pigments considerably improve the total absorption power of green plants. 

The performance of the pigments considerably depend on the system in which they are processed and applied. 

Animals that do not readily accept pelleted feeds may be enticed to do so if the feed carries an odor that induces ingestion. Color development is an important consideration in aquarium species and some animals produced for human food. External coloration is desired in aquarium species. Pink flesh in cultured salmon is desired by much of the consuming pubHc. Coloration, whether external or of the flesh, can be achieved by incorporating ingredients that contain pigments or by adding extracts or synthetic compounds. One class of additives that imparts color is the carotenoids. 

Other pigments are consumed in considerably smaller amounts. Moreover, the market data for these pigments are not as readily available as those for carbon blacks, titanium dioxide, and iron oxides. 

To produce the titanium white mtile pigment, the hydrated Ti02 gel prepared in the presence of mtile seeds is calcined at temperatures of 900—930°C. This temperature is quite important because pigments having a particle size of 200—400 nm are produced at these temperatures. When the calcination is carried out at temperatures above 950°C, the particles of Ti02 become considerably larger and do not have optimum pigmentary properties. 

Two blue pigments can be prepared in transparent form cyanide iron blue and cobalt aluminum blue. These pigments are used in achieving a blue shade of the metal effect pigments in metallic paints. Transparent cyanide iron blue is prepared by a precipitation reaction similar to the one used for the preparation of the opaque pigment, but considerably lower concentrations of solutions are used. It is produced by Degussa (Germany), Manox (U.K), and Dainichiseika (Japan). 

These pigments are sensitive to heat and bleed ia most paint solvents. They are, however, resistant to acids and bases. Their tinctorial strength is considerably greater than that of inorganic yellows but they are weaker than the diaryUde yellows. They are used extensively ia emulsion paints, paper coating compositions, inks (qv), and, depending on particle size, can ia some cases be used outdoors because of excellent lightfastness ia full shades. 

In the dyestuff industry, anthraquinone still ranks high as an intermediate for the production of dyes and pigments having properties unattainable by any other class of dyes or pigments. Its cost is relatively high and will remain so because of the equipment and operations involved in its manufacture. As of May 1991, anthraquinone sold for 4.4/kg in ton quantities. In the United States and abroad, anthraquinone is manufactured by a few large chemical companies (62). At present, only two processes for its production come into consideration manufacture by the Friedel-Crafts reaction utilizing benzene, phthahc anhydride, and anhydrous aluminum chloride, and by the vapor-phase catalytic oxidation of anthracene the latter method is preferred. 

The choice of parameter used in the determination of size distribution should include consideration of the information needed in the interpretation of the data. For example, in the case of a manufacturer of paint pigment, the size parameter that best describes the hiding power (performance of the pigment) is the projected area of particles. A powdered catalyst manufacturer is primarily concerned with surface-area equivalence. 

The quaHty, ie, level of impurities, of the fats and oils used in the manufacture of soap is important in the production of commercial products. Fats and oils are isolated from various animal and vegetable sources and contain different intrinsic impurities. These impurities may include hydrolysis products of the triglyceride, eg, fatty acid and mono/diglycerides proteinaceous materials and particulate dirt, eg, bone meal and various vitamins, pigments, phosphatides, and sterols, ie, cholesterol and tocopherol as weU as less descript odor and color bodies. These impurities affect the physical properties such as odor and color of the fats and oils and can cause additional degradation of the fats and oils upon storage. For commercial soaps, it is desirable to keep these impurities at the absolute minimum for both storage stabiHty and finished product quaHty considerations. 

Natural Sensitizing Dyes and Photodynamic Therapy. The chlorophylls are, of course, among the natural sensitizers for photosynthesis. Considerable iaterest exists ia chlorophyll and related pigments as photosensitizers ia biology and medicine (75), isomeric retinal chromophores as visual pigments (76,77), and the use of synthetic photosensitizers ia neurobiology (9), hematology (78), and photodynamic therapy (79). 

Thus the requirement for the use of man-made drugs and dietary additives as veterinary medicines for the treatment of farmed animals is considerable and worth about 100 million pounds sterling annually in the UK ( 104 million in 1994j io jjjg investment in dietary additives such as vitamins, trace minerals, coccidiostats, pigmenters, enzymes and other probiotics to feed compounders in the UK is worth about 110 million, assuming an addition rate of 2.5 kg per tonne and a cost of approximately 3% of the total concentrate dietary cost (calculated from MAFF data, 1995). ° These data can be increased by a factor of about 10 when the compound feed produced within Europe is considered. 

In general the selection of pigments for polypropylene follows the same considerations as for polyethylene. Because of the higher processing temperatures and the lesser resistance to oxidation, selection does, however, require rather more care. 

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