A Worldwide Search for Rhenium

The mineral samples they found are rare and contain very low contents of rhenium. 

Some examples from their analysis are given in Table 29.1. 

With renewed support from Notgemeinschaji, Walter and Ida Noddack could take home a considerable quantity of molybdenum ore from Norway. Its rhenium content was 2-4 mg per kg. The ore was treated at the tantalum factory of Siemens Halske, and the one gram goal agreed upon was reached in the summer 1929. The Noddacks now possessed the large rhenium quantity of 3 g. 

High Concentrations oTRhenium are Unexpectedly Found at Home  

The sludge, containing copper, molybdenum, nickel, iron, vanadium and rhenium, was dried and then allowed to weather in air for several months. This treatment oxidized the sulfides to sulfates. The weathered sludge was leached with water. Concentration by evaporation led to precipitation of the sulfates of calcium, copper and nickel. Ammonium sulfate was added to the mother liquor and nickel ammonium sulfate precipitated. Vanadium and molybdenum were then precipitated as polyphosphates. 

---