Abstract: An analytical test, color change reagent preparation comprising peroxidase, an oxygen-oxidoreductase specific to a particular substance to be tested and a chromogen-reactive-indicator formula selected from (a) those having the general formula ##STR1## wherein X is the divalent carbonyloxy or sulfonyloxy group, W is hydrogen or another cation compatible with the aforesaid other ingredients of said reagent preparation, the subscript n is 0 or 1, and (i) when X is the carbonyloxy group, A is a divalent alkylene chain with from 2 to about 7 carbons, and (ii) when X is the sulfonyloxy group, n is 0 when A is the divalent alkylene chain of from 2 to about 7 carbons, and n is 1 when A is straight chain trimethylene or tetramethylene, and (b) the acid addition salts of said disubstituted benzidine derivative, compatible with the aforesaid ingredients of the chromogen-reactive-indicator, when X is the carbonyloxy group.

Abstract: Disclosed are benzidine derivatives substituted in each of the 3,3'-positions by the substituent ##STR1## wherein W is hydrogen or an alkali metal, the subscript n is zero when A is the divalent branched chain alkylene having from 2 to about 7 carbon atoms, and n is one when A is straight chain divalent alkylene with 3 or 4 carbons. Also disclosed are the corresponding derivatives wherein the sulfonyl group is replaced by the carbonyl group. Further disclosed are chromogen-reactive indicator compositions having as their chromogen constituent one of the foregoing benzidine derivatives. These compositions (1) are useful to test for a substance for which there exists a specific oxygen-oxidoreductase, such as a sugar, an amino acid, uric acid, and the like, and thus (2) contain also a peroxidase, a hydrogen-peroxide-oxidoreductase, and a specific oxygen-oxidoreductase for the specific material in the testing of which the composition is to be used.