Table 2: Chemical analysis of magnesium vapor reduced niobium powders (in ppm).

ElementNiobium pentoxide1st stage niobium powderAfter 2nd stage niobium powder

Ni<203535
W420550555
Ta92511501160
Co<20<20<20
Cr<20<20<20
Mn<10<10<5
Mg<201200925
O8%6500
Fe<20<20<20