Aurin tricarboxylic acid, ammonium

VII,10. AMMONIUM SALT OF AURIN TRICARBOXYLIC ACID ( ALUMINON )... 

Alnminon (qualitative test for aluminum). The reagent consists of 0.1% solution of the ammonium salt of aurin tricarboxylic acid. A bright red precipitate, persisting in alkaline solution, indicates aluminum. 

Aurin tricarboxylic acid [4431-00-9] M 422.4, m 300". The acid is dissolved in aqueous NaOH, NaHS03 solution is added until the colour is discharged and then the tricarboxylic acid is ppted with HCI [Org Synth Coll Vol I 54 1947]. Do not extract the acid with hot water because it softens forming a viscous mass. Make a solution by dissolving in aqueous NH3. See Aluminon for the ammonium salt. 

Formaldehyde condenses with salicylic acid in the presence of nitrite-containing sulphuric acid to give aurin tricarboxylic acid this is converted by ammonia solution into the ammonium salt, which is employed as a reagent for aluminium ( aluminon ) ... 

Aluminum in solution of its salts is detected by the reaction (1) with ammonium salt of aurin tricarboxylic acid ( aluminon ), which yields a red precipitate persisting in NH4OH solution, (2) with alizarin red S. which yields a bright red precipitate persisting in acetic acid solution. 

Aluminon (a solution of the ammonium salt of aurine tricarboxylic acid) Quinalizarin, alizarin-S, alizarin Chromium (III), Cr3 Ammonia solution... 

---