Subject pigment synthesis

Cochineal pigments are extracted from dried bodies of female insects with water or with ethanol the result is a red solution that is concentrated in order to obtain the 2 to 5% carminic acid concentration customary for commercial cochineal. For carmine lakes, the minimum content of carminic acid is 50%. An industrial procedure applied in Spain uses ammonium hydroxide as the extracting agent and phosphoric acid as the acidifying agent. For analytical purposes the extraction is carried out with 2 N HCl at 100°C. The chemical synthesis of carminic acid has also been reported and is the subject of European and United States patents. ... 

The synthesis of carbonyl colorants uses a wide diversity of chemical methods, in which each individual product essentially has its own characteristic route. This is in complete contrast to the synthesis of azo dyes and pigments (Chapter 3) where a common reaction sequence is universally used. The subject is too vast to attempt to be comprehensive in a text of this type. The following section, therefore, presents an overview of some of the fundamental synthetic strategies which may be used to prepare some of the more important types of carbonyl colorants. 

The early work by Gripenberg et al. on P. sanguinea infected wood afforded the dark red pigment xylerithrin (118) and its simple derivative 5-O-methylxylerythrin (119) [97, 98], The synthesis of 118 was carried out also by other authors [99], Subsequently, the related peniophorin (120) [100] and peniophorinin (121) were isolated [101], Both compounds were subjected to further confirmative X-ray studies, allowing the unambiguous location of all hydroxy group in the former [101], and a revision of the structure for the latter [102, 103],... 

A synthesis of the nanosized pigments on a basis of zinc phosphates was the subject of the investigation with the use of the chemical methods of synthesis, electron microscopy and electrochemical impedance spectroscopy. 

The synthesis of Vitamin D3 in vivo takes place in the skin. UV-B radiation ( = 290-315 nm) cleaves 7-dehydrocholesterol, an intermediate product of cholesterol metabolism, in the epidermis, which isomerises spontaneously at body temperature to cholecalciferol. While the photolysis is very efficient, it is subject to seasonal and climatic fluctuations. Strong pigmentation and aged skin lead to a considerably reduced capacity to produce Vitamin D. 

Although the synthesis of polymer colloids has been known for almost a century, the elaboration of organic/inorganic particles is only in its infancy. Some fifty years ago, early methods focused primarily on pigment encapsulation for the paint industry, and were mainly motivated by the problem of pigment dispersion. Since then, research interest in polymer-encapsulated minerals and the so-called colloidal nanocomposites has exploded such that the subject now relates to a wide variety panel of inorganic particles including mineral oxides, aluminosilicates, metal colloids, and semiconductors. 

---