Radium compounds

Radium, Ra, is a radioactive metallic element. There are 14 radioactive isotopes of radium however, only radium 226, with a half-life of 1620 years, is usable. It is a brilliant, white solid that is luminescent and turns black upon exposure to air. Radium is water-soluble, aud coutact with water evolves hydrogeu gas. It is iu the alkaliue-earth metal family aud, like calcium, it seeks the boues wheu it euters the body. It is highly toxic aud emits iouiziug radiatiou. Radium is destructive to liviug tissue. 

An x-tay machine at a hospital is a source of radiation only when the machine is turned on. There is no radioactive source when the power is off. 

It is used in the medical treatment of malignant growths and industrial radiography. Compounds formed with radium all have the same hazards as radium itself. Most are used in the treatment of cancer and for radiography in the medical and industrial fields. The compounds are all solids, and the degree of water solubility varies. Radium bromide has a molecular formula of RaBr2 it is composed of white crystals that turn yellow to pink. It sublimes at about 1650jF and is water-soluble. The hazards are the same as for radium. It is used in the medical treatment of cancers. 

Radium carbonate, with the molecular formula of RaCOj, is an amorphous, radioactive powder that is white when pure. Because of impurities, radium carbonate is sometimes yellow or pink. It is insoluble in water. 

Radium chloride, with the molecular formula of RaClj, is a yellowish-white crystal that becomes yellow or pink upon standing. It is radioactive and soluble in water. It is used in cancer treatment and physical research. 

---

We must now more fully consider the radium emanation — a substance with more astounding properties than even the radium compounds themselves. By distilling off the emanation from some radium bromide, and measuring the quantities of heat given off by the emanation and the radium salt respectively, Professors Rutherford and Barnes proved that nearly three-fourths of the total amount of heat given out by a radium salt comes from the minute quantity of emanation that it contains. The amount of energy liberated as heat during fre decay of the emanation is enormous one cubic centimetre liberates about four... 

In addition to being radioactive, radium is extremely chemically reactive and forms many compounds. These radium compounds are not only radioactive but also toxic and should be handled by experienced personnel. 

Uranium mineral first is digested with hot nitric acid. AH uranium and radium compounds dissolve in the acid. The solution is filtered to separate insoluble residues. The acid extract is then treated with sulfate ions to separate radium sulfate, which is co-precipitated with the sulfates of barium, strontium, calcium, and lead. The precipitate is boiled in an aqueous solution of sodium chloride or sodium hydroxide to form water-soluble salts. The solution is filtered and the residue containing radium is washed with boiling water. This residue also contains sulfates of other alkahne earth metals. The sohd sulfate mixture of radium and other alkahne earth metals is fused with sodium carbonate to convert these metals into carbonates. Treatment with hydrochloric acid converts radium and other carbonates into chlorides, all of which are water-soluble. Radium is separated from this solution as its chloride salt by fractional crystallization. Much of the barium, chemically similar to radium, is removed at this stage. Final separation is carried out by treating radium chloride with hydrobromic acid and isolating the bromide by fractional crystallization. 

Since the discovery of radium compounds, many radio-active substances have been isolated. Only exceedingly minute quantities of any of them have been obtained. The quantities of substances used in experiments on radio-activity are so small that they escape the ordinary methods of measurement, and are scarcely amenable to the ordinary processes of the chemical laboratory. Fortunately, radio-activity can be detected and... 

Like all radioactive elements, it undergoes continuous, spontaneous disintegration into elements of lower atomic weight. M. and Mme. Curie had noticed that when air comes into contact with radium compounds it, too, becomes radioactive. The correct explanation was first given in... 

Table 3-2 lists important physical properties of radium and selected radium compounds. Radioactive properties of the four naturally-occurring radium isotopes are listed in Table 3-3. In addition to the naturally occurring isotopes, there are 12 other known isotopes of radium. The principal decay schemes of the uranium and thorium decay series that produce the naturally-occurring radium isotopes are presented in Figure 3-1.

Pure metallic radium oxidizes when exposed to air, but radium compounds suspended in air are not subject to transformation or degradation mechanisms. 

Physical and Chemical Properties. Although some of the physical and chemical properties of radium and radium compounds have not been determined, many of those that are needed to evaluate its behavior in the environment are known. The adsorption-desorption behavior of radium with geologic materials depends on the specific system under study and should be determined on a case-by-case basis. Also, thermodynamic and kinetic data for solid solution formation are scarce. Research in this area would facilitate modeling the fate of radium in water. 

The presence of radium in biological materials or environmental samples is generally determined by virtue of its radioactivity. Except in the laboratory where radium compounds have been isolated and determined for a certain purpose, determination of radium compounds in biological and environmental samples is relatively rare. As a Group IIA alkaline earth element, radium is similar in its chemical behavior to other members of that group, especially its nearest neighbor, barium. For example, radium tends to precipitate as the sulfate, which is the basis for its isolation for chemical analysis by coprecipitation with barium sulfate. Furthermore, radium associates with calcium in living systems and accumulates in bone. The determination of radium compounds or specific isotopes is usually accomplished by a separation procedure, followed by quantitative analysis of total radium based on its radioactivity. 

Barium platinocyanide, after prolonged exposure to radiation from radium compounds, becomes brown or red and loses its fluorescent properties. The only way to completely restqje the red crystals to their fluorescent state is by solution and recrystallisation,1 although gentle heating will partially restore them. This is well illustrated by the following table ... 

Radium. Compounds of radium are closely similar to those of barium. The only important property of radium and its compounds is its i v idioactivity, which is discussed in Chapter 33. 

Uses. — Radium compounds find a limited use in such instruments as the spinthariscope, Fig. 6, and Strutt s radium clock. The latter is an electroscope so arranged that the leaves are alternately charged by radium and discharged by grounding. It is a curious contrivance which transforms the radiating energy of radium into motion which approaches perpetual. (SeeFig. 7.)... 

The two most important commercial uses for radium compounds at present are in medicine and in the manufacture of luminous paint. 

The formula for calcium oxide is CaO. What are the formulas for magnesium oxide and strontium oxide A common mineral of barium is barytes, or barium sulfate (BaS04). Because elements in the same periodic group have similar chemical properties, we might expect to find some radium sulfate (RaS04) mixed with barytes since radium is the last member of Group 2A. Flowever, the only source of radium compounds in nature is in uranium minerals. Why ... 

Rutherford sought for a similar gaseous emanation from radium compounds, but the quantity of these at his disposal was too small. Within a few months, however, Dorn detected the presence of the gas and three years later Debiernet found that actinium behaved likewise. The three emanations are now known as thoron of half-life 54 secs., radon 3 825 days, and actinon. 3 9 secs. 

IVIarie and Pierre Curie first discovered that air in contact with radium compounds became radioactive. Later experiments by Ernest Rutherford and others isolated the radioactive substance from the air. This substance was an isotope of the noble gas radon (Rn). 

Although the chemistry of radium is relatively simple (like barium), the fact that it produces a radioactive gas (radon) complicates its handling. The decay of radon produces "airborne" radioactive atoms of At, Po, Bi, and Pb. Since uraniiun is a common element in rocks (see 5.4) it is also a common constituent of building materials. Such material emits Rn, as discussed further in 5.6. Work with radium compounds should be carried out within enclosures to avoid exposure to Rn and its daughters. 

Marie Curie, Nobei prize discoverer of the eiements radium and poionium, carried out iaborious recrystaiiization experiments in order to eventually isolate very small amounts of a radium compound from the uranium ore pitchblende, obtained from Bohemian mines. The work was carried out in an old shed and took years of effort - the ore had to be cmshed and stirred with various solvents to remove the... 

His equipment was similar to Marsden s, a small brass box fitted with stopcocks to admit and evacuate gases from its interior, with a scintillation screen mounted on one end. For an alpha source he used a beveled brass disk coated with a radium compound ... 

Intensity of Radiation Radiation Exposure Radioactive Elements and Compounds Uranium Compounds Radium Compounds... 

Shortly after radioactivity was discovered, people thought that radiation had certain curative powers. Radium compounds were made and radium solutions were bottled and sold for drinking and bathing. That was before people knew the harmful effects of radiation exposure—and some early users of these cures paid a dear price for acquiring that knowledge. Today s medical practitioners are much wiser. They have devised sophisticated ways to use radionuclides to examine patients, diagnose their illnesses, and treat their disorders. 

---