Finger Blood Method for Micro-Kjeldahl Non-Protein Nitrogen

Into a centrifuge tube, pipette 10 cc. of Folin's micro-tungstic acid solution. Make a reasonably deep wound in the finger to be assured of an adequately free and natural flow of blood, as squeezing appears to contaminate the sample. Using an accurate, capillary-bore pipette, draw up 0.1 cc. of blood. Carefully discharge the blood at the bottom of the centrifuge tube, and rinse the pipette with the clear supernatant solution; mix thoroughly. Allow to stand 2 or 3 minutes, and centrifuge. Decant the clear solution and apply a 4% correction for solution in the precipitate (or use a 5 cc. aliquot) and conduct a micro-Kjeldahl digestion. Collect the ammonia by distilling into 5 cc. of 0.1 N HCl. Fill the receiver tube containing the HCl up to the 25 cc. mark with distilled water, and add 5 cc. of Nessler's solution drop by drop while stirring. Add 5 cc. of the Nessler's solution to 25 cc. of the standard ammonium sulfate solution which should contain 0.1 mg. of nitrogen. Nesslerize the unknown and the standar...