8.5 After 60 t 5 min,add cthanol up to the 50-mL mark,mix,and return to the waterbath;8.5 After 60 t 5 min,add cthanol up to the 50-mL mark,mix,and return to the waterbath;then after another 60 t 5 min,measure the absorbence of the solution with a spectrophotometer at 630 nm.To avoid corrosion of the instrument by HCI fumes,the cells or cuvettes should be covered 8.6 Read the number ofmilligrams ofxylan in the test specimen from a previously prepared calibration graph(see Section 12)then after another 60 t 5 min,measure the absorbence of the solution with a spectrophotometer at 630 nm.To avoid corrosion of the instrument by HCI fumes,the cells or cuvettes should be covered 8.6 Read the number ofmilligrams ofxylan in the test specimen from a previously prepared calibration graph(see Section 12)