T 3825 (OTTO) Tantalum chunks, 1-10 mm, 99.95% Cas 7440-25-7 - used is in the manufacture of heating elements, vacuum tubes and other high temperature parts. T 3825 (OTTO) Tantalum chunks, 1-10 mm, 99.95% Cas 7440-25-7 - used for electronic components, and due to its absorption properties, tantalum is an excellent getter of residual gasses in evacuation tubes.