Thermophysical Properties of Aqueous Piperazine and Aqueous (N-Methyldiethanolamine + Piperazine) Solutions at Temperatures (298.15 to 338.15) K Muhammad, A.; Mutalib, M.I.A.; Murugesan, T.; Shafeeq, A.; Journal of Chemical & Engineering Data 2009, 54, 2317-2321