B. Alkaline TiTration Method
Place 10-20 g sample, ground to pass No. 20 sieve, in 800 mL Kjejdahl flask, add approxinately 200 mL H2O and let stand 2-4 hour (Autolysis should be conducted with apparatus completely connected for distillation.) Steam distil, collect 150-160 mL distillaet in NaOH solution (0.5 g in 20 mL H2O), and dilute to definite volume.
To 100 mL distillate (it is preferable to dilute to 250 mL and titrate 100 mL aliquot) add 8 mL 6 newton NH4OH and 2 mL 5% KI solution and titrate with 0.02newton AgNO3, using microburet. End point is faint but permanent turbidity and may be easily recognized, especially against black background.
1 mL 0.0.2N AgNO3=1.08 mg HCN (Ag equivalent to 2 CN)