METHOD OF PRODUCING UNIVERSAL ACID-BASE INDICATOR PAPER Russian patent published in 2012 - IPC D21F11/14 G01N31/22 

FIELD: chemistry.

SUBSTANCE: universal acid-base indicator paper for determining pH of a solution is obtained by saturating chromatographic paper with a solution of a mixture of acid-base indicators and a fixing agent. The fixing agent used is tetraalkylammonium halide with content thereof in the solution of 0.2-2.0 wt %, which is selected from: tetramethylammonium chloride, bromide or iodide, tetraethylammonium chloride, bromide or iodide, tetrapropylammonium chloride or bromide, trimethyloctylammonium bromide, wherein the solution of the mixture of acid-base indicators and fixing agent is turned yellow by 0.1 n sodium hydroxide solution.

EFFECT: invention enables to obtain a universal acid-base indicator paper, having contrast colour transitions on a wide pH scale, from 2 to 12, resistance to washing off of the resultant colour after contact with the analysed sample, which enables to determine pH in aqueous solutions, suspensions and emulsions with high accuracy.

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