2(1H)-quinolinethione derivatives as organic reagents. II. Properties of some 2(1H)-quinolinethione derivatives and application to the potentiometric titration of the silver ion.

Halogen derivatives of 2 (1H)-quinolinethione, alkyl derivatives of 1, 2-dihydro-2-thioxo-4-quinolinecarboxylic acid, and alkyl 1, 2-dihydro-2-thioxo-4-quinolinecarboxylate were synthesized. The detection limits for metal ions with these reagents were examined by spot tests. The metal ions which gave a precipitate with these reagents were the same as those reported previously. iso-Amyl 1, 2-dihydro-2-thioxo-4-quinolinecarboxylate (ATQ) forms a 1-to-1 compound with silver, and an ethanolic solution of ATQ was used as a titrant to determine 0.01-0.0001 M silver ions potentiometrically. The coefficient of variation was 1.8% (n=10) for 107.4 μg of silver. Silver protein was titrated potentiometrically with ATQ in 50% (v/v) ethanolic solution. The silver content was 8.0%, with a coefficient of variation of 1.8% (n=5).