1908 Journal of the American Medical Association  
and to heat until the fumes of the nitrogen oxids arise faintly, in this way furnishing the mixture of nitric and nitrous acids. The acid is then poured into another clean, dry test tube and, after superimposing the urine on the slightly yellow nitric acid, the usual play of colors is looked for. An error in interpretation, not of the presence of bile, but of the presence of albumin, in the urine is remotely possible after this manipulation. In practically every test made in this way a distinct
more » ... white ring can be seen between the urine and the acid in nonalbuminous urines after the lapse of less than a minute, often at once. This ring, which is practically always just below or associated with the normal brown ring, is sometimes so dense and sharp that under some conditions, remembering the usual Heller's test for albumin, a faulty conclusion respecting the albumin content of a urine may be made. Heating the acid alone to boiling will never give the same result, and the white ring in question is probably precipitated resin dissolved from the wood by the nitric acid. This resin can not be removed by ordinary means. Benzin will not remove it completely, or will give a cloud at the juncture of the urine and the acid after its removal from the benzin. Alcohol is impracticable, for it mixes with the acicl. Consequently,
doi:10.1001/jama.1908.25310470028002e fatcat:mltmy7vtovax5oxad2bekw2j3y