Fig. 2

Assessment of the visual colorimetric change in the boron (2.50 g L^− 1) + silicon mixture (1.00; 1.25 and 1.50 g L^− 1) immediately (a) and 360 min after solution preparation (b); and boron (2.50 g L^− 1) + silicon mixture (1.00; 1.05; 1.10; 1.15; 1.20 and 1.25 g L^− 1) at 0 (c); 60 (d); 120 (e); 180 (f); 300 (g) and 360 (h) min after solution preparation