Umudike Journal of Engineering and Technology

There is no mathematical model that relates the enthalpy, composition and temperature for sulphuric acid-water solution mixtures; rather it is presented in chart. In this research work, the solubility data for sulphuric acid-water mixtures which are usually represented in enthalpy-concentration charts was reduced to empirical models. Double variable Chebyshev polynomial of the first kind was used to formulate models for the solution enthalpy of sulphuric acid-water system as a function of concentration and temperature at 1 atmosphere by developing the models for the different segments of the chart. The solution concentration and temperature ranges covered were 0-100 wt% H₂SO₄ and 0-160^oC, respectively. The data fitting was carried out with Table Curve 3D software. Eight models were generated and each model predicted the experimental solution enthalpy values to a maximum absolute error of less than 4%. Equations (7) to (14) have maximum percentage errors of ±2.75, ±1.58, ±1.75, ±1.39, ±1.78, ±3.66, ±3.5, ±2.92 and degrees of fit of 5, 4, 4, 5, 3, 3, 2, and 2   respectively. The double Chebyshev polynomial fitted the data very well for every segment of the chart and the models are very reliable.