RADIUM 



Radium ( La1 . rtxliti.i. ray ). One 

 of the chemical elements. Its chemi- 

 cal symbol is Ra, atomic weight 

 226, melting point 700 C. (1,292 

 F.). Discovered by M. and Mme 

 Curie in 1898, it was isolated in 

 1910 from radium chloride. It is a 

 silver-white metal, which tarnishes 

 rapidly on contact with air. 



The chief source of radium is the 

 mineral pitchblende, in which it 

 appears in minute quantities, only 

 a few grains to the ton, and from 

 which it is extracted by a lengthy 

 process. The uranium of the ore is 

 removed and the residue treated 

 with hot caustic soda, hydrochloric 

 acid, and a strong solution of 

 sodium carbonate, which gives a 

 mixture of radium and barium 

 carbonates. There are usually 

 various impurities present, e.g. 

 lead, calcium, etc. These are 

 chemically separated, the process 

 converting the radium and barium 

 carbonates into chlorides. These 

 last two are separated by fractional 

 crystallisation. Radium is re- 

 markable for its' radio-active pro- 

 perties. In addition to pitchblende 

 deposits of Joachimsthal in N. 

 Bohemia, and elsewhere, the ele- 

 ment is recovered from the mineral 

 carnotite in the U.S.A., etc. 



Radium is extensively used in 

 medicine, especially in certain types 

 of skin diseases, e.fj. tuberculous 

 lesions, in cases of exophthalmic 

 goitre, sarcoma, carcinoma, rodent 

 ulcer, etc. It has been given in- 

 ternally in certain forms for rheu- 

 matism. The element has also been 

 used in the treatment of cancer, but 

 the results are not sufficiently cer- 

 tain yet to say that it provides a 

 cure for the disease. During the 

 Great War radium and all radio- 

 active substances were controlled. 

 In Great Britain and the U.S.A. 

 Radium Institutes exist for the 

 supply, investigation, and medical 

 treatment by the element. The 

 address of the London Radium In- 

 stitute is 16, Riding House Street, 

 W. See X-rays ; Uranium ; Carno- 

 tite; consult also The Interpreta- 

 tion of Radium, F. Soddy, 1909. 



Radius. Outermost of the two 

 bones of the forearm. It articu- 

 lates at its upper end with the 

 humerus and the ulnar, and at its 

 lower end with the scaphoid and 



Radius 



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lunar bones of the wrist. The upper 

 extremity or head is disk-shaped, 

 and has a depression in the centre 

 which articulates with a protuber- 

 ance on the humerus. At the side 

 of the disk is the articular surface 

 which rotates in the small sigmoid 

 cavity of the ulna. On the upper 

 part of the shaft of the bone is a 

 rough tuberosity to which is at- 

 tached the tendon of the biceps. 



The muscles attached to the 

 shaft are the flexor sublimis 

 digitorum, the flexor longus polli- 

 cis, the pronator quadratus, ex- 

 tensors of the thumb, the pronator 

 teres, and the supinator brevis. The 

 lower extremity has a large surface 

 for articulation with the wrist, and, 

 on its inner side, a small surface 

 which articulates with the ulna. A 



RADNOR 



Radius (Lat., rod, ray). In geo- 

 metry, name given to the straight 

 line drawn to the circumference of 

 a circle or the surface of a sphere 

 from their centres. 



Radius Vector . In astronomy, 

 name given to the line joining the 

 position of a planet at any point 

 in its orbit to the sun. Since the 

 planetary paths are ellipses, the 

 length of the radius vector varies, 

 and the shorter it becomes the 

 faster the planet moves. This fact 

 is stated in Kepler's second law, 

 that the areas described by the 

 radius vector of a planet in its orbit 

 are proportional to the times taken 

 in describing them. 



Radlett. Village of Hertford- 

 shire, England. It is 5 m. from S. 

 Albans and 15 m. from London, 



Radley College, Berkshire. School buildings and chapel 



Radius. Diagram illustrating relative position of 

 bones of the forearm 



sharp protuberance of the bone, 

 which can be felt on the outer side 

 of the wrist, is known as the stiloid 

 process. When the arm is held in 

 the position of supination, i.e. with 

 the palm facing forwards, the 

 radius is parallel to the ulna. When 

 the arm is turned into the position 

 of pronation, i.e. with the back of 

 the hand facing forwards, the 

 radius is crossed over the ulna. 



Dislocation of the radius, which 

 usually results from a fall on the 

 hand, is most frequently in a 

 forward direction, the head of the 

 radius coming to rest against the 

 lower end of the humerus. Reduc- 

 tion is effected by pulling on the 

 wrist with the forearm bent at a 

 right angle, pressure over the head 

 of the bone being applied at the 

 same time. Following reduction 

 the arm should be kept at rest for 

 several weeks. 



Fracture of the radius may occur 

 at any part of the 

 5 bone, but is most 

 1 frequent at the 

 j lower end, being 

 usually due to a fall 

 in which the hand 

 is stretched out 

 palm downwards 

 to break the fall. 

 This is known as 

 C o 1 1 e s's fracture 

 (q.v.) See Arm. 



on the Mid. Rly., and is a residen- 

 tial suburb of London. 



Radley. Village of Berkshire, 

 England. It stands on the Thames, 

 4 m. from Oxford, and has a station 

 on the G. W. Rly. S. John's Church 

 is a modern building, and the hall, 

 once the seat of the Bowyer family, 

 is now the college. Pop. 900. 



Radley College. English public 

 school. Founded at Radley, near 

 Oxford, in 1847, its full name is the 

 College of S. Peter. It is a Church 

 of England school, incorporated by 

 royal charter in 1890, and has 

 about 200 boys. A memorial 

 gateway has been erected, inside 

 the double arches of which are 

 inscribed the names, records, and 

 portraits of the boys and masters 

 who fell in the Great War. 



Radnor, NEW. Village of Rad- 

 norshire, Wales. It stands on the 

 river Somergill, 7 m. from Pres- 

 teigne, with a station on the G.W. 

 Rly. At one time a place of some 

 size, it was incorporated in 1561, 

 and retained its municipal privi- 

 leges until 1883. There are remains 

 of its castle, once a stronghold of 

 the Mortimers, and part of the 

 guildhall is shown. .About 3 m. 

 to the S.E._ is the village of Old 

 Radnor, wnich also had a castle. 

 The waterfall known as Water- 

 break-its-neck is 3 m. to the W. of 

 New Radnor. Pop. 400. 



