Stains and Dyes

The aminophenols are versatile intermediates and their principal use is as synthesis precursors their products are represented among virtually every class of stain and dye. 

The derivatives of the aminophenols have important uses both in the photographic and the pharmaceutical industries. They are also extensively employed as precursors and intermediates in the synthesis of more compHcated molecules, especially those used in the staining and dye industry. All of the major classes of dyes have representatives that incorporate substituted aminophenols these compounds produced commercially as dye intermediates have been reviewed (157). Details of the more commonly encountered derivatives of the aminophenols can be found in standard organic chemistry texts (25,158). A few examples, which have specific uses or are manufactured in large quantities, are discussed in detail in the following (see Table 6). 

At one time, uranium was considered to be a relatively unimportant element. It had a few applications in the making of stains and dyes, in producing specialized steels, and in lamps. But annual sales before World War II (1939—1945) amounted to no more than a few hundred metric tons of the metal and its compounds. 

Another difficulty with the direct microscope count is the fact that the method views both viable and nonviable (dead) cells. Depending on stage in the growth cycle, as well as history of the sample, the ratio of viable to nonviable cells may vary considerably and makes comparing results to those of direct plating difficult. Because of this, plating normally provides lower estimates of viable populations than microscopy. To make the distinction between viable and nonviable cells, various stains and dyes can be used either singly or in combination (Section 14.4.2, 14.4.3, and 14.4.4). 

Both fiber producers and fabric mills have realized that many of the performance variants that are difficult to iacorporate iato fiber melt spinning can be accompHshed by post-treating yams or fabrics. Mills ia the 1990s can apply flame retardants, softeners, dye-fade inhibitors, and stain- and soil-resisting agents as part of the finishing of a fabric. 

This mixture is known as Quinoline Yellow A [8003-22-3] (Cl 47000) and is most widely used with polyester fibers (109). Upon sulfonation, the water-soluble Quinoline Yellow S or Acid Yellow 3 [8004-92-0] (Cl 47005) is obtained. This dye is used with wool and its aluminum salt as a pigment. Foron Yellow SE-3GL (Cl Disperse Yellow 64) is the 3-hydroxy-4-bromo derivative. Several other quinoline dyes are commercially available and find apphcations as biological stains and analytical reagents (110). 

There are various types of wood stains and criteria used to choose the right type for a job. Although there are several distinct groups or types of stains, it is safe to categorize wood stains into two groups dye stains and pigmented stains. 

Another form of equalizing stains is through the use of sap stain. Color differences between the sapwood and late-growth area of the lumber can be made uniform by using this type of stain. Sap stains are usually alcohol-based dye stains that tie lighter areas of the wood into darker areas. Transparency of sap stain and equalizers is important to ensure a natural, nonpainted appearance. 

The color and effect produced by NGR stains and any stain mixture depend on several factors other than the colors or type of dyes used. Those factors include strength of the mixture, the amount appHed, the type of substrate, and the solvent system used for the stain. The role of the wood stain is not to provide protection rather, the primary function of the stain is to impart color effects by accentuating grain patterns. The transparency and brightness needed to enhance the natural beauty of the wood are optimized by using dye-type stains for wood. 

A good example of the effect of regulations on wood stains is the issue surrounding methanol (qv). Methanol is the most widely used solvent for wood stains because of its fast-drying properties, low cost, and the solubiHty of dyes in methanol. Because methanol is Hsted by the U.S. EPA as a ha2ardous air poUutant (HAP), and because of the extremely low soHds of wood stains, it is most likely that wood stains such as NGR, body stains, and sap stains will need to be reformulated before the end of the twentieth century. 

Preparation for Dyeing. A hot alkaline scour with a synthetic surfactant and with 1% soda ash or caustic soda is used to remove size, lubricants, and oils. Sodium hypochlorite is sometimes included in the alkaline scouring bath when bleaching is requked. After bleaching, the polyester fabric is given a bisulfite rinse and, when requked, a further scouring in a formulated oxahc acid bath to remove mst stains and mill dkt which is resistant to alkaline scouring. 

Basic dyestuffs are usually used for dyeing of unbleached pulp in mechanical pulp such as wrapping paper, kraft paper, box board, news, and other inexpensive packaging papers. Their strong and brilliant shades also make them suitable for calendar staining and surface coloring where lightfastness is not critical. 

W. Yu, W. K. Dodds, M. K. Banks, J. Skalsky, and E. A. Strauss, Optimal staining and sample storage time for direet micro.scopic enumeration of total and active bacteria in soil with 2 fluore.scent dyes, Appl. Environ. Microbial. 61 3367 (1995). 

There is a strong limitation in the concentration range due to the logarithmic relationship between transmission and concentration (optical densities reasonably to measure range from 0.1 to 1.5). Nevertheless, protein quantification by direct UV-measurement or after staining with dyes in the visible range is a very robust method and can be found, e.g., as a common detection mode in HPLC or other chromatographic techniques. 

These dyes, already described in section 2.12, require adequate solubility for the coloration of various organic solvents and must be cheap [79]. The simplest and least polar dyes of this class are used for the coloration of petrol and ball-pen inks, with more polar types being used in lacquers, stains and varnishes. Some products of lower solubility are used in mass coloration. 

Polymeric beads obtained via emulsion polymerization, precipitation, etc. can be stained with dyes providing that both have functional groups available [7]. Covalent coupling is mostly preferred but the attachment based on strong electrostatic interactions is also feasible. This method is mostly used to design pH- and ion-sensitive micro- and nanobeads. The dynamic response of such systems can be... 

---