3667. Eriochrome(R) Black T (Ciba)

Nomenclature

CAS number: 1787-61-7
3-Hydroxy-4-[2-(1-hydroxy-2-naphthalenyl)diazenyl]-7-nitro-1-naphthalenesulfonic acid sodium salt (1:1); 3-hydroxy-4-[(1-hydroxy-2-naphthalenyl)azo]-7-nitro-1-naphthalenesulfonic acid monosodium salt; C.I. Mordant Black 11; C.I. 14645.
C20H12N3NaO7S; mol wt 461.38.
C 52.06%, H 2.62%, N 9.11%, Na 4.98%, O 24.27%, S 6.95%.

Description and references

Prepn: Hagenbach, US 790363 (1904 to Geigy); Colour Index vol. 4 (3rd ed., 1971) p 4067.

Chemical structure

Properties

Brownish-black powder with a faint metallic sheen. Sol in hot water giving a reddish-brown soln when cold. Violet-brown precipitate with excess HCl. Deep blue, then red in aq soln of NaOH. Sol in concd H2SO4 giving a blackish-blue soln which yields a brown precipitate on dilution.

Use

To dye wool from an acid bath reddish-black, which can be converted to blue-black by afterchroming. As indicator for complexometric titrations and in the determn of the total calcium and magnesium content of water.