A 5.25 mg sample of protein was digested to convert all nitrogen (AW 14.01) to

ammonia before the sample was diluted to volume in a 100-mL volumetric flask.

Then, 5.0 mL of this solution was pipetted into a 50-mL volumetric flask, treated

with phenol that forms a blue-colored product with ammonia and diluted to volume.

The product gave a net absorbance of 0.486 at 625 nm in a 1.00 cm cell. A

standard containing 0.518 ug N /mL gave a net absorbance of 0.184 in a similar

1.00 cm cell. Calculate the w/w % of nitrogen in the protein.