Definition of Allen test

Allen test

1. for phenol: on the addition of 5 or 6 drops of hydrochloric acid and then 1 of nitric acid to the suspected fluid, a red color develops;
2. for strychnine: fluid is extracted with ether, which is then evaporated by means of “drop-by-drop” pipetting into a warmed porcelain dish or crucible; the residue is treated with drops of manganese dioxide and dilute sulfuric acid; a red-blue or violet color develops if strychnine is present.
3. a test for radial or ulnar patency; either the radial or ulnar artery is digitally compressed by the examiner after blood has been forced out of the hand by clenching it into a fist; failure of the blood to diffuse into the hand when opened indicates that the noncompressed artery is occluded.

[A.H. Allen]