Public domain
Dr. D.C. Bardwell, of the Research Lab. of the U.S. Bureau of Mines, collecting gaseous radium emanation. The radium is in the little safe at the right. Collections are made at intervals of from 4 to 10 days. The gas is drawn off under vacuum and purified by a liquid air refrigeration. The purified
From the collection of Library of Congress. Free to download, adapt and use — no permission needed.
Subjects
Credit lineDr. D.C. Bardwell, of the Research Lab. of the U.S. Bureau of Mines, collecting gaseous radium emanation. The radium is in the little safe at the right. Collections are made at intervals of from 4 to . 1924-01-01. Harris & Ewing. Harris & Ewing Collection, Library of Congress. Public domain.