University of San Francisco - USF Don Yearbook (San Francisco, CA)

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BA DIO-ACTIVE SI BSTAXCES 37 Radium. Radium is the only now radio-element that has so far been isolated in the form of pure compounds, or which has been found to give a new spectrum. The quantities of pure radium compounds obtained are excessively small. Only a few tenths of a gram of radium chloride can be extracted from a ton of pitchblende, and this is in the ratio of one part to several millions of the original mineral. On the other hand, the radio-activity of the pure compound is correspondingly increased, and the tiny quantity extracted from a ton of ore retains in concentrated form the greater part of the radio-activity of the original mineral. Weight for weight, the radium compounds arc at least a million times more active than the compounds of uranium and thorium. The atomic weight of radium is 225 which places it in the position of the third heaviest element known, the two heavier being the other radio-elements—thorium 232 and uranium 238. Source and Method of Extraction. Radium is now obtained chiefly from carnotitc, though a small amount is derived from pitchblende. Practically all of the world’s radium until nine years ago, came from deposits in Portugal. The first important radium operations in the United States did not commence until 1912, although a small plant designed to recover uranium from carnotitc ore was erected in Colorado in 1900. The following method of the treatment of radium extraction has been taken from Madame Curie’s Thesis on the subject:—To extract the uranium, the ore is roasted with sodium carbonate, lixiviated with warm water and then with dilute sulphuric acid, when the uranium passes into solution. The insoluble part consists of the sulphates of lead and calcium, alumina, silica and iron oxide, together with greater or less quantities of nearly all the metals. These residues possess an activity four and one-half times that of uranium, and constitute the raw material used for the extraction of radium.

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26 T1IE I (iS AT I AN spontaneously give out heat and other manifestations of energy which are able to affect a photographic plate; to cause certain substances to fluoresce; and to render the air in their neighborhood a conductor of electricity. These other manifestations of energy are called rays; and from this comes the term radio-activity. Three different kinds of these rays arc distinguished; the alpha, beta, and gamma rays. The alpha rays are responsible for most of the ionization of the air produced by radio-active substances; they can penetrate the air only a few centimeters and are easily stopped by paper. They are connected with the development of the greater part of the heat evolved by such substances. When uninfluenced by external forces they move in straight lines, but under the influence of an electrostatic or a magnetic field, they are slightly bent out of their path and act as though they consisted of a stream of rapidly moving particles charged with positive electricity. The beta rays are more penetrating than the alpha rays and pass readily through paper and even through thin sheets of metal. They are especially active toward a photographic plate. Like the alpha rays they move in a straight line, unless influenced by a magnetic or electrostatic field when they are deflected in the opposite direction from that in which the alphas are turned, and much more strongly. The gamma rays arc characterized by extraordinarily great penetrating power, being able to pass through bodies which will stop the other forms of radiations. No deviation of these rays has been detected in the most powerful magnetic fields it is possible to obtain, and in this respect they arc more nearly allied to the X-rays than to the alpha and beta rays; but in their absorption by different kinds of matter they exhibit an almost complete parallelism to the beta rays. Their effects are insignificant compared with that of the other two types.

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28 THE IGX AT I AS The insoluble sulphates are converted into carbonates by boiling with a concentrated solution of carbonate of soda, and the soluble sodium sulphate produced is removed by repeated washing. The residue is treated with hydrochloric acid, which dissolves most of it, including the polonium and actinium, but the radium remains undissolved, as unconverted sulphate . It is washed with water, again boiled with concentrated sodium carbonate (which completes the transformation of the sulphates into carbonates), again thoroughly washed, and then treated with dilute hydrochloric acid free from sulphuric acid. Polonium and actinium are still present in the solution, from which the radium and barium are removed by precipitating with sulphuric acid. From 1 ton of residues 10kg. to 20kg. of crude sulphates are thus obtained, of activity about sixty times that of uranium, and these contain calcium, lead, iron and a trace of actinium. The sulphates are transformed into chlorides as before, and the solution treated with sulphuretted hydrogen, filtered, oxidised with chlorine and precipitated with ammonia. The activity of the precipitated hydrates and oxides is due to actinium. The filtrate is precipitated with sodium carbonate, and the precipitate washed and converted into chlorides, evaporated to dryness, and the chlorides washed with concentrated hydrochloric acid, which removes calcium. The purified chlorides of barium and radium thus obtained possess an activity of about fiO. Eight kilos are obtained from 1 ton of residues. At this stage the material leaves the factory, and is now fractionated in the laboratory. Practical Uses of Radium. Apart from its role of importance in the world of science, radium is today, recognized as a tremendous factor in the world of medicine and industry. The medical fraternity has come to accept radium as a beneficial treatment for cancer. Permanent cures have been accomplished, and practically every large city has at least one hospital that is supplied with a small quantity of radium. In actual practice the surgeon