Artificial radioactive elements have found extensive application in chemistry, physical chemistry, and especially in biochemistry, as indicators in the study of metabolic processes. For example, organic compounds containing pa2 or C '1 have been synthesized in the animal body, 1 in plants, 2 and in vitro.a, 4 Little attention has been given to S a~ apparently on account of its very soft beta rays which make quantitative measurements difficult. Recently Miss R. G. Franklin, of this Foundation, has reported 5 on the biological synthesis of glutathione .6 by yeast grown in a medium containing MgS*O4. The author has now succeeded in synthesizing in vitro two compounds containing radioactive sulfur, 4,4'dinitrodiphenyl disulfide* and p-nitrobenzenesulfonyl chloride*, which are intermediates in the synthesis of the biologically important sulfanilamide*.
S a5 was obtained as a by-product in the bombardment of CC14 with neutrons accelerated by the Cyclotron of the Biochemical Research Foundation, located at the Bartol Research Foundation. The S a5 was then isolated, after the addition of ordinary sulfur, by distilling off the CC14. Only 55 mg. of S* with an activity of 345 counts per minute for I mg. were available. This sample contained about IO per cent. of carbonaceous material, due to an accident in distilling off the