Sudan III Fat Stain

Microscopy reagent Sudan III Fat Stain for microscope use.

Sudan III Fat Stain

Sudan III for fat. Sudan III, or azo-benzene-azo/3-naphthol, was introduced by Daddi into histology in 1896 (Arch. Ital. De Biologic, t. 26, p. 142), as a specific stain for fat. As it is soluble in all forms of fat and oils and in xylene, alcohol, etc., it is impossible to mount specimens in balsam after staining. As the fat of tissues is removed by the reagents used in the paraffin and collodion methods, only teased, free-hand, or frozen sectioned material fresh or fixed in some non-fat dissolving fixer can be used (Muller's fluid and 5 % f ormaldelhyde are excellent) . The tissues cut free-hand or with the freezing microtome or teased can then be stained with a saturated alcoholic solution of the Sudan. It stains all fat a brilliant red. Preparations can be preserved in glycerin or glycerin jelly. This stain is largely used in pathology.

Daddi used the substance to feed animals and thus to stain the fat which was laid down in the body while the Sudan was fed.

The fat in the body already deposited remains unstained. This substance then serves to record the deposit of fat in a given period. In 1907 Dr. Oscar Riddle fed Sudan to laying hens, and the fat in the layers of yolk laid down during the feeding was stained red (Science, XXVII, 1908, p. 495). For staining the yolks of hen's eggs the hen may be fed doses of 20 to 25 milligrams of the Sudan. Eggs so colored hatch as usual, and the chick in utilizing the colored yolk stains its body-fat pink (Susanna P. Gage).

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