Urea

Urea osmotic pressure vs. molality at different temperatures

Reference: Stokes, R. H. "Thermodynamics of aqueous urea solutions." Australian Journal of Chemistry 20, no. 10 (1967): 2087-2100.https://doi.org/10.1071/CH9672087. 

Robert Harold Stokes
molality, mol/kg20C50C100C200C250C300C400C
0.50.4870.4870.4880.4890.4900.4910.491
10.9500.9520.9550.9600.9620.9640.968
1.51.3941.3981.4051.4161.4201.4251.432
21.8231.8301.8411.8591.8661.8731.885
2.52.2392.2502.2652.2912.3022.3122.330
32.6452.6592.6792.7142.7292.7432.766
3.53.0413.0593.0853.1293.1483.1663.197
43.4303.4513.4833.5383.5623.5833.621
54.1884.2174.2624.3394.3724.4024.455
64.9244.9635.0215.1205.1645.2045.274
75.6455.6925.7645.8885.9435.9936.081
86.3546.4106.4966.6466.7106.7706.877
9 7.1247.2237.3947.4697.5387.662
10 7.8417.9508.1398.2218.2978.431
11   8.8818.9669.0449.180
12   9.6299.7079.7789.899

Urea osmotic pressure vs. molality at 25 degrees Celsius

Reference: Shumilin, Ilan, Ahmad Tanbuz, and Daniel Harries. "Deep Eutectic Solvents for Efficient Drug Solvation: Optimizing Composition and Ratio for Solubility of β-Cyclodextrin." Pharmaceutics 15, no. 5 (2023): 1462. https://10.3390/pharmaceutics15051462. 

Shumilin et al.
molality, mol/kgOsmolality, Osmolal
0.1010.091
0.1770.151
0.2530.227
0.5060.479
0.7630.717
0.9980.924
1.0120.939
1.2001.094
1.2711.166
1.4001.258
1.5201.370
1.6011.423
1.7651.574
1.8031.584
1.9971.745
2.0001.821
2.0171.783
2.1231.900
2.5132.148
2.9932.616
2.9962.481
4.0133.479
4.9924.277
6.0325.139
7.0005.838
7.9866.665
8.9967.422
9.9738.144
11.0058.902
11.9709.739

The data set is adequately captured by the quadratic fit:
Osmolal = -0.00711m^2 + 0.89132m.