Sodium hydrogen bicarbonate (99.7%), sodium carbonate (99.9%), and ammonium carbamate (98%) were supplied by Sigma-Aldrich (Steinheim, Germany).
Brooker, "Ammonium carbonate, ammonium bicarbonate, and ammonium carbamate equilibria: a raman study," Journal of Physical Chemistry[R], vol.
Although ammonium carbonate (([NH.sub.4])[H.sub.2][CO.sub.3]), ammonium bicarbonate ((N[H.sub.4])HC[O.sub.3]), and
ammonium carbamate (([NH.sub.4])[H.sub.2]NC[O.sub.2]) have significant vapor pressures, they are easily handled as solids and can be compounded with BUR without difficulty.