This method is for determining rhenium in relatively pureperrhenic acid and ammonium perrhenate over a concentration rangefrom 40 to 70 mass-%. Molybdenum is an interference when it ispresent at concentrations higher than 10% of the rhenium content.Molybdenum can be determined by UOP Method 833. Other elements thatproduce colored ions in the dissolution or color-development stepconstitute a positive interference.