Stable ferrous-ferric nitrate solutions for fischer-tropsch catalyst preparation

A method of producing a stable Fe(II)/Fe(III) nitrate solution comprising ferrous nitrate and ferric nitrate and having a desired ratio of ferrous iron to ferric iron, the method comprising:

• obtaining a stable ferrous nitrate solution by dissolving iron in a nitric acid solution consisting of aqueous nitric acid having a first nitric acid concentration to form a ferrous nitrate solution and maintaining the solution at a first emperature for a first time period greater than thirty minutes;
• dissolving iron in nitric acid having a second nitric acid concentration to form a ferric nitrate solution, wherein the second nitric acid concentration is greater than the first nitric acid concentration;
• maintaining the ferric nitrate solution at a second temperature;
• and
• combining amounts of stable ferrous nitrate solution and ferric nitrate solution to produce the stable Fe(II)/Fe(III) nitrate solution having the desired ratio of ferrous iron to ferric iron,
• wherein the Fe(II) content of the stable Fe(II)/Fe(III) nitrate solution changes by less than about 2 weight percent over a time period of at least one day.