Letters Sent to Dudley S. Ingraham, December 11, 1928

December 11th,1928. Mr. Dudley S. Ingraham, The E. Ingraham Company, Bristol, Conn. Dear Ingraham: Mr. Lee has handed me your letter of December 6th, in which you enclosed a letter of the same date addressed to Dr. Stoll. In the main you have covered the situation,as we outlined it to you, very well in your letter to Dr. Stoll, but there are one or two points which I believe we had better clarify: Pure radium, that is the element, does not exist commercially as such. When we speak of refined radium we ordinarily mean one of the salts, such as the chloride, bromide or sulphate. Radium occurs in native ores in complex combinations, the exact nature of which varies in different ores. Radium continuously produces its first docay product, radon, which is a gas. This gas has what is known as a one half decay period of 3.85 days, which means that after 3.85 days one half of the amount present at any given time has decayed. It is possible to remove this gas from a radium preparation, and it is common practice to do this for use by the medical profession. However, it must be rememberod that when the gas radon is separated from the parent radium, and starts to decay there is being formed a new quantity of gas by the parent radium at the same rate as that which has been separated is decaying. Different radium compounds vary in their property of freely emitting this gas radon - that is, from some preparations the gas doés not escape, but lives and dies in the preparation itself. Other preparations emit the gas, and it may become dissipated through out the air or wherever the preparation exists. In this connection we speak of various compounds emitting varying percentages of the radon produced. That is radium as chloride or bromide has what is commonly termed a free emanating property of 10 to 12%. Radium sulphate 3% to 5%. Native carnotite ores exhibit a free emanating property of 15 to 25%, while it is rare that the native pitchblend exhibits a free emanating property exceeding 5% In this connection it is of interest to note that radium when mixed with zine sulphide exists there as radium sulphate whose free emanating property does not exceed 5%, which means that 95% of the gas, radon, lives and dies within the compound itself, and not more than 5% excapes into the atmosphere. It is for this reason that we maintain that there is not sufficient gas existing in the atmosphere of the ordinary application plant to constitute a hazard.