Color Pigments in General

As this new technology, which can find virtually any amount in any media, is applied to other areas, it continues to have profound impacts. We have aU seen reports of the new blood and tissue testing of humans which has uncovered Usts of trace substances in extremely minute quantities. It is only in recent years that these analytical results became technically possible. Instead, a nondetect level would be given below which we would assume zero or a level of no concern. We will now see these methods used in laboratory toxicology tests on test animals and cells. The results will create a never ending equivocal debate over how much is safe, since, for the first time, positive numbers above zero will be reported in final laboratory conclusions. 

There are so few issues that would apply to only one pigment that this general discussion should cover most of the issues for all color pigments. We have discussed briefly the shifting and disappearing de minimis level. 

We now have the PBT-TRI reporting rules for chlorinated contaminants and the PBT-TRI rule for lead. The PBT rule for lead will apply to all pigment production in the United States. First, we should briefly review the background for PBTs and how this evolving scheme developed. 

This movement to identify PBTs follows logically from the reaUzation that many of the most difficult environmental problems have been caused by specific organic, generally chlorinated, compounds, which include polychlorinated biphenyls (PCBs), dioxins, DDT, organic mercury, and other pestiddes. This internationally recognized list has been the subject of bans and restrictions in many countries. The issue for the near future is to find a way to define and eliminate similar compounds. 

Shortly after the first list of 80 chemicals targeted for voluntary PBT data gathering was complete, the EPA issued the Waste Minimization Prioritization Tool 

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The earlier results in the application of thin-layer chromatography (TLC) for the analysis of natural color pigments, in general, and especially in plants, have been reviewed. Pigments are more or less strongly bonded to cellulose, protein, cell-wall components, and so forth in... 

This section provides an overview of the synthesis of dyes and pigments used in textiles and related industries. Dyes are soluble at some stage of the application process, whereas pigments, in general, retain essentially their particulate or crystalline form during application. A dye is used to impart color to materials of... 

Generally, there are two basic types of inks. The first type contains finely dispersed carbon black or colored pigments in both solvent and water based systems. Pronounced improvements have been achieved in stabilizing aqueous pigment formulations for ink-jet applications by adding specific polymeric dispersing agents [18], The second type of ink is based on water or solvent soluble dyes. 

Microfiltration membranes can be used as pretreatment for other membrane technologies and to remove microbes and total suspended sohds (TSS) including fibers and particles. Retention of salts and dissolved organics is negligible, if they are not bound to the suspended sohds. MF can be used for the recovery of coating color pigments. MBRs generally use UF or MF membranes. The materials used in microfiltration are polyvinylidenefluoride (PVDF), polypropylene, polyethylene, polysulfone, polyether suUbne, Teflon, and ceramic materials. 

Cobalt as a Colorant in Ceramics, Glasses, and Paints. Cobalt(II) ion displays a variety of colors in soHd form or solution ranging from pinks and reds to blues or greens. It has been used for hundreds of years to impart color to glasses and ceramics (qv) or as a pigment in paints and inks (see CoLORANTS FOR CERAMICS). The pink or red colors are generally associated with cobalt(II) ion in an octahedral environment and the chromophore is typically Co—O. The tetrahedral cobalt ion, Co—chromophore, is sometimes green, but usually blue in color. 

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