Ferroin reagent

Abstract

3-(2-pyridyl)-5,6-bis(phenylsulfonic acid)-1,2,4-triazine and certain salts thereof, e.g.--sodium, are provided together with a method for forming such compounds. These compounds are useful as reagents in the spectrophotometric determination of iron in water or other solutions.

I claim as my invention: 
     
       1. 3-(2-pyridyl)-5,6-bis(phenylsulfonic acid)-1,2,4-triazine. 
     
     
       2. A compound having the structural formula ##STR3## wherein x is a member selected from the group consisting of hydrogen, sodium, potassium and ammonium. 
     
     
       3. The compound of claim 2 wherein x is hydrogen. 
     
     
       4. The compound of claim 2 wherein at least one x is sodium. 
     
     
       5. The compound of claim 2 wherein x is sodium. 
     
     
       6. The compound of claim 2 wherein x is potassium. 
     
     
       7. The compound of claim 2 wherein x is ammonium. .[.8. A process for making 3-(2-pyridyl)-5,6-bis(phenylsulfonic acid)-1,2,4-triazine which comprises reacting 2-cyanopyridine with at least a stoichiometric amount of hydrazine in a first solvent, cooling to precipitate 2-pyridyl hydrazidine, reacting the 2-pyridyl hydrazidine with benzil in a second solvent and allowing the precipitate of 3-(2-pyridyl)-5,6-bis(phenyl)-1,2,4-triazine to form, separating the precipitate, reacting the 3-(2-pyridyl)-5,6-bis(phenyl)-1,2,4-triazine with fuming sulfuric acid to form a reaction product, raising the temperature of the reaction product to form about 195° C. to 205° C. within less than about 30 minutes and then immediately cooling to ambient temperatures in less than 30 minutes and recovering 3-(2-pyridyl)-5,6-bis(phenyl sulfonic acid)-1,2,4-triazine..]. .[.9. The process of claim 8 wherein the first solvent is isopropanol..]. .[.10. The process of claim 8 wherein the 2-pyridyl hydrazidine is treated to remove impurities..]. .[.11. The process of claim 8 wherein the 2-pyridyl hydrazidine and the benzil are each placed in a solvent and then added together to allow reaction and the formation of 3-(2-pyridyl)-5,6-bis(phenyl)-1,2,4-triazine..]. .[.12. The process of claim 11 wherein the solvent in which the 2-pyridyl hydrazidine and the benzil are placed is isopropanol..]. .[.13. A process for making a salt of 3-(2-pyridyl)-5,6-bis(phenyl sulfonic acid)-1,2,4-triazine which comprises reacting 2-cyanopyridine with at least a stoichiometric amount of hydrazine in a solvent, cooling to precipitate 2-pyridyl hydrazidine, reacting the 2-pyridyl hydrazidine with benzil in a solvent and allowing the precipitate of 3-(2-pyridyl)-5,6-bis(phenyl)-1,2,4-triazine to form, separating the precipitate, reacting the 3-(2-pyridyl)-5,6-bis(phenyl)-1,2,4-triazine with fuming sulfuric acid to form a reaction product, raising the temperature of the reaction product to from about 195° C. to 205° C. within less than about 30 minutes and then immediately cooling to ambient temperatures in less than 30 minutes, recovering 3-(2-pyridyl)-5,6-bis(phenyl sulfonic acid)-1,2,4-triazine, adding the 3-(2-pyridyl)-5,6-bis(phenyl sulfonic acid)-1,2,4-triazine to a salt solution containing ions selected from the group consisting of sodium, potassium and ammonium and recovering a salt of 3-(2-pyridyl)-5,6-bis(phenyl sulfonic acid)-1,2,4-triazine selected from the group consisting of sodium, potassium and ammonium..].