RE: bichromate gum
The "reply-to" of Loris' message was set to his personal address instead of The List, so I post my reply again
this is for Na2Cr2O7.2H2O.sodium dichromate's (NaDi) molar mass is 298.02g
For the anhydrous form, the M.W. is 262.01. In this case the math changes accordingly.