LIEBEN'S IODOFORM TEST.—To a few cubic centimetres of the distillate a few drops of a solution of potassium and some drops of a solution of iodine and iodide of potassium are added, the solu tion of potassium being added in excess. When acetone is present, a thick, yellow precipitate of iodoform will immediately form. This test will reveal 0.01 milli gramme. By heating, the iodoform evaporates and accumulates on the sides of the test tube in the form of small yellow plaques, consisting of the charac teristic crystals of iodoform. The most serious objection to Lieben's test is that many (at least seventeen) other sub stances, and especially alcohol, may give the same result.
Lieben's iodoform test recommended both for delicacy and ease of application. A yellow opacity, with precipitation of iodoform, occurs if acetone be present. Nothing else that occurs in the urine, except acetone, is able to give this pre cipitate of iodoform, without warning.
When hut small quantities are present the urine should first he made acid with sulphuric acid and distilled. When half the urine has been distilled all the ace tone has been found to he in the die tillate. Ruttan (Montreal Med. .Tour., Mar., '9I).
The most satisfactoiT test for acetone in the urine is Lieben's. It is performed by adding, a few drops of Lugol's solution to the first 10 cubic centimetres obtained by distilling 400 cubic centimetres of fresh urine, then adding sodium-hydrox ide solution until the brown color disap pears. In the presence of acetone a milky precipitate of iodoform is produced, and may be recognized by its violet colora tion with caustic soda and thyinol, or by its yellow hexagonal crystals under the microscope. Ronsse (Annales de Gyn. et d'Obstet., Mar., 1900).