. Biological stains, a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy). zation. This reaction is ordinarily very readily reversable and makes such dyes useful indicators of acidity. It is discussed more fully under acid fuchsin (p. 64) and phenolphthalein (p. 83). CLASSIFICATION OF DYES On the basis of the chromophore present the simple synthetic dyes are classified into several groups. If each of these groups were characterized by a single color or by a few closely related colors, dye chemistry would be a comparatively simple
. Biological stains, a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy). zation. This reaction is ordinarily very readily reversable and makes such dyes useful indicators of acidity. It is discussed more fully under acid fuchsin (p. 64) and phenolphthalein (p. 83). CLASSIFICATION OF DYES On the basis of the chromophore present the simple synthetic dyes are classified into several groups. If each of these groups were characterized by a single color or by a few closely related colors, dye chemistry would be a comparatively simple proposition. As a matter of fact a single chromophore may occur in dyes of practi- cally all colors of the rainbow. It is ordinarily impossible to deter- mine, a priori, from the chemical formula of a dye what particular color the compound may have; but there is, nevertheless, a certain general rule which correlates chemical formula with color. In any group of compounds, the simpler ones are converted into the more complex by substitution of radicals for hydrogen atoms. In the dyes the substituents are generally methyl or ethyl groups, or sometimes phenyl groups. Now the general rule is that the larger the number of hydrogen atoms that have been replaced by these groups the deeper the color. The tendency is for the color of the simplest dyes in any group of homologous compounds to be yellow, passing thru red to violets and then greens and blues, as the homo- logs become higher thru the introduction of successively larger numbers of methyl or other substituting groups. Thus the com- pound pararosanilin, which is very frequently sold as basic fuchsin, but should more properly be called basic rubin, is a tri- phenyl methane, with an amino group attached to each benzene ring, but without any methyl groups; thus: H \ CI Rosanilin, which is similar in composition, but contains one methyl group attached to one of the benzene rings,. Please note that these images are extracted from sc
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