In the N determinations made using the comparative technique,
25 mL of extracts prepared by the AOAC procedure were transferred to
Kjeldahl flasks, followed by the addition of about 50 mL of 40% (m/v)
NaOH. After mounting the distillation apparatus, the solution was heated
and distilled until one third of the original volume remained. The distillate
was collected in a receiving flask containing 25 mL of 5% (m/v)H3BO
plus 75 mL of water. Four to six drops of the mixed indicator
were added to the receiving flask and the solution was then titrated
with 0.05 mol L 3−1 H2SOuntil the indicators changed color.