. Cytological technique; the principles underlying routine methods. Histology -- Technique; Cytology -- Technique. OH Alizarine. CO(CHOH);. OH Carminic acid cularly valuable dye in biological work. Carminic acid is soluble (unlike alizarine) in distilled water, and also in ethanol. It occurs naturally in the fat-body of the wingless females of the coccid Dactylopiiis cacti. This is a scale-insect that sucks the juices of the succulent plant Nopalea coccinellifera. The latter is cultivated in various subtropical parts of the world to provide the insect with food. The dried females consti
. Cytological technique; the principles underlying routine methods. Histology -- Technique; Cytology -- Technique. OH Alizarine. CO(CHOH);. OH Carminic acid cularly valuable dye in biological work. Carminic acid is soluble (unlike alizarine) in distilled water, and also in ethanol. It occurs naturally in the fat-body of the wingless females of the coccid Dactylopiiis cacti. This is a scale-insect that sucks the juices of the succulent plant Nopalea coccinellifera. The latter is cultivated in various subtropical parts of the world to provide the insect with food. The dried females constitute cochineal. Carmine is a crude form of the dye, produced by precipitating an aqueous extract of cochineal with alum (potassium aluminium sulphate). It is com- posed mainly of carminic acid bound to aluminium and to pro- tein derived from the insect. Carmine is insoluble in distilled water; but solutions can be obtained ( by the addition of acid or alkali), and the crude dye is usable in microtechnique. It is best to use the pure acid whenever one wants to know exactly what reactions are occurring. One of the main uses of carmine in microtechnique is explained in the chapter on the use of mordants (p. 122). Xanthene dyes. In these dyes, carbon and oxygen form links between two rings. Not many members of this group are com- monly used in microtechnique. Eosin, however, is particularly familiar. It is a valuable 'background' dye: that is to say, it is anionic, pale, diffuse in action, and used to give contrast with objects picked out vividly in another colour by another 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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