Tungsten pentaboride, 99% pure

Assay of tungsten (W): 87.5%
Assay of boron(B): 11.5%
Assay of tungsten (W): 87.5%
Assay of boron(B): 11.5%
"It is impossible to learn chemistry in any way without seeing the practice itself and not starting chemical operations."
(M.V.Lomonosov)