Aqueous amino acid salt solutions might be an attractive alternative over traditional alkanolamines in the removal of CO2 from flue gases especially because of their oxidative stability and negligible volatility. The density and viscosity of the aqueous solutions of the potassium salts of the following amino acids have been measured: β-alanine, 6-aminohexanoic acid, l-arginine, l-aspartic acid, l-glutamic Acid, dl-methionine, l-phenylalanine, l-proline, and sarcosine. Data are reported in the temperature range of (25 to 60) °C and concentration range of (0.25 to 3.5) mol·L−1. The data could be correlated accurately with relatively simple relations. The physical solubility of N2O in the same amino acid salt solutions was also measured at a temperature of 298 K and a concentration of 0.5 mol·L−1 of the amino acid salt. Using the N2O/CO2 analogy on one hand and Schumpe’s method on the other, the physical solubility of CO2 in these solutions was estimated. Both methods yielded results very close to each other.