Base pigment

Owing to environmental regulations, the consumption of lead-based pigments, lead chromate [7738-97-6], in particular, has been decreasing steadily at an average aimual rate of about 5% since the early 1980s. In 1993 production was estimated to be around 20,000 t (see Lead compounds). 

Cadmium-based pigments have been hit particularly hard by environmental regulations. As the result, consumption in 1993 was estimated to be between 1.5—5 thousand metric tons. The future of this pigment category is particularly questionable in North America. 

Fig. 5. Color and composition correlation of cadmium-based pigments.

A primary source of environmental pollution from printing ink comes from the metal-based pigments used, as well as various resins, waxes, and drying agents that are also part of the inks. These materials are added to inks regardless of the source of the oil. As a result, petroleum inks are just as suitable for landfill disposal under U.S. EPA regulations as are vegetable oil inks. 

The only components in a coating powder which might cause the waste to be classified as hazardous are certain heavy-metal pigments sometimes used as colorants. Lead- (qv) and cadmium-based pigments (qv) are seldom used, however, and other potentially hazardous elements such as barium, nickel, and chromium are usually in the form of highly insoluble materials that seldom cause of the spent powder to be characterized as a hazardous waste (86). 

The physical properties of the base pigments produced from both processes are further improved by sluirying in water and selectively precipitating on the finely divided particles a surface coating of Si02, AI2O3. or TiOi itself. 

TiOSUj 1 Boil to hydrolyse, and then seed to 1 produce aaataae or rutile as desired TiO, H,0 1 Wash, then calcine at 800-900 C "Base pigment ... 

An accurate observation of the first crater produced during the LIBS measurement with a camera revealed the presence of a blue substrate under the upper red layer of painting. The LIBS analysis demonstrated that the underlying blue substrate is composed by azurite (a copper based pigment) mixed with white lead (Figure 7). 

Bicchieri M., Nardone M., Russo P.A., Sodo A., Corsi M., Cristoforetti G., Palleschi V., Salvetti A., Tognoni E., Characterization of azurite and lazurite based pigments by LIBS and micro-Raman spectroscopy, Spectrochim. Acta B 2001 56 915-922. 

G. Gautier, M.P. Colomhini, GC MS Identification of Proteins in Wall Painting Samples A Fast Clean up Procedure to Remove Copper based Pigment Interferences, Talanta, 73,95 102 (2007). 

Lead arsenates, 74 797 Lead azide, 70 727-729 74 792 Lead babbitt, 3 52, 52t arsenic addition to, 3 271 Lead-base babbitts, 24 797 Lead-based paint, 74 765 Lead-based paint remediation, 18 75 Lead-based pigments, 79 386. See also Lead chromate pigments Lead benzoate, 74 794 Lead bisilicate, 74 796 Lead blast furnace, 74 737 Lead borate, 74 797 Lead bromide, 74 785 Lead bullion, 74 742, 745... 

The oldest monoazo yellow pigment is Pigment Yellow 1, which continues to be produced and shipped on a large scale. Its discovery and introduction in 1910 was followed by the development of a variety of related pigments of this type, not all of which have turned into a commercial success. A few, such as pyrazolone-based Pigment Yellow 10, are still produced by some regional companies and are targeted for smaller niche applications. 

There are a number of other media which are also pigmented with P.V.23. The list includes office articles and artists colors, such as drawing inks and fiber-tip pen inks, wax crayons, oil paints, and high quality water colors, water- or solvent-based pigmented wood stains, cleaning agents, and mass colored paper. 

Oxygenic photosynthetic bacteria include the nitrogen fixer Trtchodesmtum and the cyanobacteria Synechococcus and Prochlorococcus. The latter represent a major fraction of the microbial biomass in the ocean and are probably the most abimdant primary producers in the ocean. They were not discovered until the late 1980s, probably because of their small size as they are members of the picoplankton. These cyanobacteria are photosynthetic. They use bacteriochlorophyll a and plastocyanin, a blue Cu-based pigment, for light harvesting. 

The metabolism of several 3,3 -dichlorobenzidine-based pigments has been studied in animal experiments to determine if they are metabolized to 3,3 -dichlorobenzidine. In a study where rats were exposed by inhalation to Pigment Yellow 17 (230 mg/m air) for 4 hours, 3,3 -dichlorobenzidine was not detected in either urine or blood during the following 14 days (Hofmann and Schmidt 1993). No detectable residues of 3,3 -dichlorobenzidine were found in urine samples of hamsters administered a single dose of... 

Epidemiological and Human Dosimetry Studies. The potential for occupational exposure exists in the use of 3,3 -dichlorobenzidine in the synthesis of 3,3 -dichlorobenzidine-based pigments for printing ink applications and to a lesser extent in paints. Workers exposed to 3,3 -dichlorobenzidine (and simultaneously to other chemicals) have complained of gastrointestinal upset, upper respiratory infection. 

In metabolism studies of azo dyes and pigments in the hamster, in vivo cleavage of the benzidine-based dye, Direet Black 38, to benzidine was shown by analysis of the urine. However, studies of the 3,3 -diehlorobenzidine-based pigment. Pigment Yellow 12, showed no evidenee for in vivo cleavage to release 3,3 -diehlorobenzidine (Nony et al. 1980). 

Because the chemical has no agricultural or food chemical application, it is very imlikely that 3,3 -dichloro-benzidine occurs in food in general. [ C]-3,3 -Dichlorobenzidine was foimd to rapidly accumulate in bluegill sunfish as a result of their exposiue to water in which either 5 or 100 g/L of the chemical was intentionally added. Residues were distributed in both the edible and nonedible portions (Appleton and Sikka 1980). However, 3,3 -dichlorobenzidine was not detected in fish samples obtained from rivers near nine textile dyestuff manufacturers known to use 3,3 -dichlorobenzidine-based pigments (Diachenko 1979). 

NIOSH, in 1980, concluded that dming the use of benzidine-based dyes, the greatest potential for exposme would be expected to be by dermal absorption or inhalation by personnel who routinely handle dry powders (NIOSH 1980). However, EPA (1980b) has generalized that dermal absorption in the workplace is probably a minor route of 3,3 -dichlorobenzidine exposure, although dermatitis has occurred in workers in plants where 3,3 -dichlorobenzidine and 3,3 -dichlorobenzidine-based pigments were manufactured. It may be that health risks with regard to 3,3 -dichlorobenzidine exposme depend on the specific operations of the individual plant and the extent of personal protective practices of the individual operator. 

Decad GM, Snyder CD. 1983. Fate of water insoluble and water soluble dichlorobenzidine based pigments in Fischer 344 rats. J Toxicol Environ Health ll(3) 455-465. 

Hofmann T, Schmidt D. 1993. Investigation of possible metabolism of pigment yellow 17, a 3,3 -dichlorobenzidine-based pigment, after inhalation exposure in rats. Arch Toxicol 67(2) 141-144. 

Figure 5.19 Metal oxide - mica based pigments.

Silica and alumina based pigments. These new substrate materials, SiO and Al Oj which were developed by Merck, are absolntely flat and therefore allow the production of very intense interference colonrs that can be coupled with a variety of goniochromic properties." ... 

Metal reflector plate based pigments. Metal reflector based systems, developed by DuPont, Flex Products and BASF," consist of a metal disc, usually aluminium, coated with a dielectric layer, such as SiOj or MgF, followed by an ultra-thin transparent layer or an absorbing layer, e.g. FejOj. Some of the possible combinations are shown in Figure 5.20. 

FIG. 4. A comparison of the pupillary (Lucas et al 2001) and circadian action spectra which best fit an unidentified vitamin A-based pigment with a between 479-481 nm, with the absorbance spectrum of a flavoprotein photopigment, and the action spectrum iot Arabidopsis CRYl. See text for details. (Smyth et al 1988), (Ahmad et al 2002). 

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