Report, January 25, 1926

A Few Significant Facts to be Kept in Mind in Considering the Poesible Effects of Radium and Nesothorium on the Human Organism. 1. Mesothorius decays 250 times as rapid as radium and conse- quently in its pure state, weight for weight, its activity would greatly exceed that of radium. However, the quantity of meso- thorium is not expressed in milligrams by weight, but it is rated in terms of radium, thus the activity of two compounds compared bear the same ratio as the values assi ned to the preparations. 2. Although meso horium itself is rayless, its first product, which is rapidly formed after mesothorium has been separated, gives powerful beta and gamna radiations. Consequently, in the commercial production of mesothorium the operator must protect himself against these penetrating radiations This is not so necessayin the commercial production of radium as the product giving rise to the penetrating gamn radiation (Ra C) ia formed rather slowly. 3. The half value period of radium is 1580 yenra while that of mesothorium is 6.7 years. This is of impotance in consider- ing the accumulative effects of naterial that may be deposited in the system. 4. In the decay of radium we have as the first product the emanation with a half period of 3.8 dyas, followed by the active deposit of rapid change (RaA, RaB, RaC), and then the active deposit of slow change (RaD, Raz, RaF). Radium D and E enit aoft beta cays and have half periods of 16.5 years and 4.85 dygs respectively. Radiun P or Polonium enits alpha rays and has a half period of 136.5 days. In the case of mesothorium the emanation has a half period of 54.5 seconds, which is followed Th A, B, & C, comparable to the active deposit of rapid change in the radium series. ThC is followed by Thorium D (Th lead) which is stable It is important to note, that while there is generated from Radon a product of comparatively long life emitting alpha rad- iatuon there is no similar product generated in the thorium series. 5. The maximum range of an alpha particle from the thorium series is 8.6 cm, while from the radium series it is 6.94 em. H. H. Barker. Physical Laboratory, January 25, 1926