. Cytological technique; the principles underlying routine methods. Histology -- Technique; Cytology -- Technique. Skeleton-formula for haematein dyes O Haematein Catechol formula shows, this is not only an acid dye, but actually an acid, related to catechol. It is of a brownish-red colour, but becomes blue in alkaline solution. It is therefore used as an indicator of pH, but it is not valuable by itself as a dye. When used with an intermediary or 'mordant' (p. 110) between itself and the tissues, it becomes one of the most important dyes used in micro- technique. Haematein is derived from the
. Cytological technique; the principles underlying routine methods. Histology -- Technique; Cytology -- Technique. Skeleton-formula for haematein dyes O Haematein Catechol formula shows, this is not only an acid dye, but actually an acid, related to catechol. It is of a brownish-red colour, but becomes blue in alkaline solution. It is therefore used as an indicator of pH, but it is not valuable by itself as a dye. When used with an intermediary or 'mordant' (p. 110) between itself and the tissues, it becomes one of the most important dyes used in micro- technique. Haematein is derived from the heart-wood of a small legum- inous tree, Haematoxylon campechianum, native to Central America. This contains a non-quinonoid substance, haematoxylin, which is not a dye and is indeed colourless, since it lacks a chromophore; but it is readily oxidized to haematein by weak oxidizing agents, including atmospheric oxygen. Haematoxylin is often sold in a partially oxidized form, as a brown powder that is really a mixture of haematoxylin and haematein. Anthraquinonoid dyes. These are related to anthraquinone, a yellow, crystalline substance. The simplest is alizarine, the chief coloured constituent of madder, a vegetable dye. Alizarine is easily synthesized from anthraquinone. It is not used in micro- technique. Its more complex relative, carminic acid, is a parti-. 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 Baker, John Randal, 1900-. London, Methuen; New York, Wiley
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