Lately, while testing a urine for acetone by means of Lieben's and also Gunning's test, I found both tests to be negative when applied to the urine direct,but positive when applied to the distillate. Naturally, one would think that some substance was present in the urine interfering with the formation of iodoform, the reaction on which the above-mentioned tests are based.
This urine gave a marked reaction for protein and it was found that it was the presence of this substance which interfered with the above tests on account of the fact that after removal of the protein by means of dilute acetic acid, the urine responded to Lieben's and to Gunning's test.1
It is well recognized that only the distillate of the acidified urine should be used for acetone tests, but many workers often apply Lieben's test to the urine direct and if it is found to be
Rosenbloom J. A DISTURBING FACTOR IN LIEBEN'S AND IN GUNNING'S TEST FOR ACETONE IN URINE. JAMA. 1912;LIX(6):445. doi:10.1001/jama.1912.04270080127022