Congo Red
Structural Formula Vector Image
Title: Congo Red
CAS Registry Number: 573-58-0
CAS Name: 3,3¢-[[1,1¢-Biphenyl]-4,4¢-diylbis(azo)]bis[4-amino-1-naphthalenesulfonic acid] disodium salt
Additional Names: C.I. Direct Red 28; sodium diphenyldiazo-bis-a-naphthylaminesulfonate; C.I. 22120
Molecular Formula: C32H22N6Na2O6S2
Molecular Weight: 696.66
Percent Composition: C 55.17%, H 3.18%, N 12.06%, Na 6.60%, O 13.78%, S 9.21%
Literature References: Prepn: Böttiger, DRP 28753 (1884); Frdl. 1, 470; Whitehead, Chem. Trade J. 77, 386 (1925); Kline, J. Chem. Educ. 15, 129 (1938). Purification: Bedaux et al., Pharm. Weekbl. 98, 189 (1963). See also Colour Index vol. 4 (3rd ed., 1971) p 4166; H. J. Conn's Biological Stains, R. D. Lillie, Ed. (Williams & Wilkins., Baltimore, 9th ed., 1977) p 148. Toxicity: Richardson, Dillon, Am. J. Med. Sci. 198, 73 (1939). Clinical evaluation as diagnostic aid: E. Ouchi et al., Tohoku J. Exp. Med. 118, Suppl., 191 (1976). Use in combination with Sirius red as histological stain: I. R. Hinds, Lab. Med. 16, 366 (1985).
Properties: Brownish-red powder. Absorption max (pH 7.3): 488 nm (E1%1cm 595). Sol in water (yellowish-red) and in ethanol (orange); very slightly sol in acetone. Practically insol in ether. LD50 i.v. in rats: 190 mg/kg (Richardson, Dillon).
Absorption maximum: Absorption max (pH 7.3): 488 nm (E1%1cm 595)
Toxicity data: LD50 i.v. in rats: 190 mg/kg (Richardson, Dillon)
Derivative Type: Congo Red Paper
Additional Names: Riegel's paper; Herzberg's paper
Properties: Paper charged with a 0.1% aq soln of Congo Red.
Use: As indicator, usually in 0.1% aq soln for estimating free mineral acids, particularly in presence of organic acids. pH: 3.0 blue-violet, 5.0 red. Detecting and estimating free HCl in gastric contents; detecting acidity of papers. As addition to culture media; reagent for bitter-almond water; dye; biological stain.
Therap-Cat: Diagnostic aid (amyloidosis).
Keywords: Diagnostic Aid.

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