. Biological stains, a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy). XH3CI +0 XH. leuco-fuchsin Ordinarily this reaction is reversable under conditions favoring oxidation. It is of especial significance to the bacteriologist, as dj^es can often be used as indicators of reduction. Certain dyes form a still different type of leuco compound, often called a "; We have seen that the basic dyes ordinarily occur as salts of some colorless acid; now, in the case of certain dyes, notably the tri-phenyl methanes
. Biological stains, a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy). XH3CI +0 XH. leuco-fuchsin Ordinarily this reaction is reversable under conditions favoring oxidation. It is of especial significance to the bacteriologist, as dj^es can often be used as indicators of reduction. Certain dyes form a still different type of leuco compound, often called a "; We have seen that the basic dyes ordinarily occur as salts of some colorless acid; now, in the case of certain dyes, notably the tri-phenyl methanes and xanthenes (Chapters VI and VII), as soon as the acid radical is removed, the compound becomes colorless. This is because a rearrangement of the atoms in the molecule takes place upon neutralization so as to give, not the true dye base, but a compound known as a carbinol (see p. 59) in which the chromophore does not occur. Thus the theoretical base of fuchsin which should be obtained upon removal of the acid radical is: CH3 \ C=/ The compound actually formed, however, is the pseudo-base or carbinol:. H,N In this compound, it will be readily seen, there is no chromophore; hence it is colorless. These pseudo-bases are of little significance to the biologist, but they are of importance to the dye manufacturer as intermediates in the preparation of dyes. In the case of many acid dyes the chromophore is similarly broken bj^ a rearrangement of the atoms which occurs on neutrali- 19. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Conn, H. J. (Harold Joel), 1886-1975; Ambler, Joseph Alfred, 1889-; Kornhauser, S. I. (Sidney Isaac), 1887-1959; Mallory, Frank Burr, 1862-1941; Sharp, Lester W. (Lester Whyland), b. 1887. Geneva, N. Y. , The Commission
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