The degree of conversion of ammonium carbamate into urea and water is determined from both sides of the reaction over the temperature range 135 to 200 degC in Rezistal No. 4 reactors al a weight-volume ratio of 0.9 gram per cc. Similar data are obtained starting from the urea-water side of the reaction in sealed glass tubes at the higher weight-volume ratio of 1.0 gram per cc. The yields of urea are in every case higher than those obtained by other investigators working at lower weight-volume ratios. The effect of the variation of the weight-volume ratio on the yield of urea is studied in sealed glass tubes at 170' C. The range covered is 0.2 to 1.0 gram per cc. Empirically the yield of urea is found to be a linear function of the reciprocal of the weight-volume ratio.