. Biological stains; a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy); Stains and Staining; Dyes. 24 Biological Stains The double bonds in benzene are believed not to be fixed but to oscillate between adjacent carbon atoms. The importance of benzene in organic chemistry is because of the infinite number of ways in which it can combine with other radicals and elements, forming compounds of extreme complexity. If the elements in such compounds are combined in certain ways the substance is colored, and such colored compounds, af
. Biological stains; a handbook on the nature and uses of the dyes employed in the biological laboratory. Stains and staining (Microscopy); Stains and Staining; Dyes. 24 Biological Stains The double bonds in benzene are believed not to be fixed but to oscillate between adjacent carbon atoms. The importance of benzene in organic chemistry is because of the infinite number of ways in which it can combine with other radicals and elements, forming compounds of extreme complexity. If the elements in such compounds are combined in certain ways the substance is colored, and such colored compounds, after slight additional changes in the molecule, become dyes. In this respect the colored benzene derivatives are unlike the colored pigments of simpler composition; many of the latter may show intense color, but do not act as dyes. One type of substitution in the benzene ring is specially impor- tant in dye chemistry. Two atoms or groups having two'valency bonds instead of one may also replace two hydrogen atoms, pro- vided the replacement takes place simultaneously and the hydro- gen atoms replaced are situated either in the ortho or in the para position to each other. Thus two oxygen atoms (which are bi- valent) may replace two hydrogen atoms (which are monovalent) forming the compound known as quinone 0611400, the formula for which is o It /\ HC CH I 11 O or as commonly written. In printed formulae, such as those that follow in this book, the quinone ring is often abbreviated still further by omitting the double bonds within the ring. The substituent atoms or groups may or may not be alike, so long as both have two valency bonds entering into the combination. This type of substitution involves a rearranging of the double valency bonds in the benzene ring; and in compounds of this type, called quinoid compounds, the double bonds are supposed to be fixed, not mobile as in benzene. This. Please note that these images are extracted from scanned page images that may have been digi
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