Independent variables | Code levels | ||
−1 | 0 | +1 | |
Initial concentration of dye (mg/l) or (absorbance (a.u) at 212 nm) | 12.31 or (0.500 a.u) | 21.155 or (0.875 a.u) | 31.540 or (1.250 a.u) |
I (A) | 0.5 | 1 | 1.5 |
NaCl (g/l) | 1 | 3.5 | 6 |