water bath and heat the mixture while stirring for approximately one hour. The solution should initially be very dark and almost black in appearance, but as the reaction proceeds, deep maroon plate-like crystals form as a crust on the surface of the reaction mixture.
Cool the reaction mixture and vacuum-filter the product. Do not wash the product with water. Dry it in air. Weigh the dried product and calculate the percent yield (Eq. 8 and 9).
CO(NH2)2 + H2O 6 2NH3 + CO2 (8)
Cr3+ + 3CH3COCH2COCH3 + 3NH3 6 3NH4+ + Cr(CH3COCHCOCH3)3 (9)
The urea undergoes slow hydrolysis, liberating ammonia, which then controls the pH of the reaction mixture.
Determine the melting or decomposition point.