Table 1. Resolved Design of Four Factors and Three Levels with Two Center Points.

experiment	NaNO3 (g/L)	Na2CO3 (mL/L)	K2HPO4 (mL/L)	trace metals (mL/L)
8	1.0	6	0.7	0.3
2	0.4	2	0.7	0.3
26	0.7	4	0.23	0.9
4	0.4	6	0.7	0.7
9 (C)	0.7	4	0.23	0.5
23	0.7	4	0	0.5
21	0.7	0	0.23	0.5
11	0.4	2	0.7	0.7
20	1.3	4	0.23	0.5
10	0.4	2	0.08	0.3
13	0.4	6	0.7	0.3
18 (C)	0.7	4	0.23	0.5
24	0.7	4	0.85	0.5
6	1	2	0.7	0.7
12	0.4	6	0.08	0.7
1	0.4	2	0.08	0.7
7	1	6	0.08	0.7
22	0.7	8	0.23	0.5
17	1	6	0.7	0.7
3	0.4	6	0.08	0.3
25	0.7	4	0.23	0.1
15	1	2	0.7	0.3
14	1	2	0.08	0.7
19	0.1	4	0.23	0.5
5	1	2	0.08	0.3
16	1	6	0.08	0.3