Early studies (Gmelin 1824) at the University of Tübingen on the biological effects of uranium indicated that uranium salts given by mouth present a hazard as a feeble poison, but facilitating death after intravenous injection. This work with pure uranium oxide prepared from pitchblende in the form of uranyl citrate, sulfide, and chloride was performed on experimental dogs and rabbits by oral and intravenous administration of uranium salts. The oral administration of uranium in the form of sulfate (300 mg) or nitrate (900 mg) did not demonstrate any immediate symptoms, whereas 4 g of uranyl nitrate produced emesis in dogs. Chloride salt given by a gastric tube (2 g) produced death in a rabbit in 52 hours.
Pathomorpho- logical examination showed diffuse gastric inflammatory changes with leukocyte
extravasation. Intravenous administration of 600 mg of uranyl nitrate or 180 mg of chloride killed a dog within a minute, with autopsy findings of coagulated blood in the right ventricle and great vessels, as well as considerable pericardial effusion. Only 3 out of 18 metals reported in Gmelin's work produced similar findings: barium, palladium, and uranium (26).