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