Non-bleeding indicators and dyes therefor used in pH determination process

US4029597A · kind A · utility

Assignee

• E. Merck A. G.

Inventors

• Karlheinz Neisius · Darmstadt, DE
• Wilhelm Baumer

Key dates

• Filing date: Aug 6, 1975
• Grant date: Jun 14, 1977
• Expiry date: Aug 6, 1995

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/31504
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In colorimetric indicators comprising a carrier such as cellulose saturated with one or more azo dyes having reactive groups capable of forming a chemical bond with the carrier material, the improvement wherein the indicator is made non-bleeding by using such dyes which, in addition to the reactive group, contain at least one additional sulfonic acid and/or carboxylic acid group, an example of such a dye being 4-anilino-3'-(2-hydroxysulfonyloxyethylsulfonyl)-azobenzene-6'-carboxylic acid.