Florence Test

FLORENCE TEST (Florence, 1896), a microcrystalline test proposed by Florence for determining the presence of semen in forensic investigations of suspicious objects. For this purpose, Florence proposed the following reagent: potassium iodide 1.65, pure iodine 2.54, distilled water 30.0. Since the object under examination is usually some tissue (e.g., clothing), the reaction is performed as follows: a small piece is cut from the stain and moistened with distilled water on a watch or slide, then pressed out, and a drop of the extract is mixed with a drop of Florence's reagent. Very quickly, brownish-red crystals form, which are needle-shaped or rhombic, and sometimes resemble Teichmann crystals. Florence crystals form better with sufficient concentration of seminal extract, for which the drop obtained from the stain is recommended to be somewhat concentrated by drying. Florence considered this reaction specific to human seminal fluid, but it was later proven that this reaction can also be obtained with a number of other substances: with animal semen, vaginal and cervical mucus even of infants, secretions of the prostate gland, putrefied human organs, egg yolk, and vegetable proteins. According to Bokarius, the substance causing the appearance of Florence crystals is choline, which forms a compound with iodine. Therefore, not being specific, the Florence test can have, like a number of other preliminary tests (see Forensic Medical Tests, Barbieri reaction), orienting value in terms of selecting an object from among stains for examination. The only conclusive evidence for the presence of semen is the finding of individual spermatozoa.