RADIOLARIA 



4912 



RADIUM 



image of the coin. This experiment proved 

 that the salts of uranium gave off rays that 

 affected the photographic plate. These rays 

 were named Bictjmril rays, and the power of 

 giving off the ray lied radiuartirity. 



Further experiments proved that thorium, polo- 

 nium and other similar substances wriv also 

 radioactive. Attempts to separate this radioac- 

 tive substance from the ores containing it were 

 made by a number of physicists, and separa- 

 tion of radium (which see) from pitchblende 

 was one of the result of tlu <t- experiments. 



Radium is the strongest radioactive substance 

 known, but the rays given off by other radio- 

 active substances produce effects similar to 

 those given off by radium and similar to the 

 effects of Roentgen rays. These effects are 

 described under RADIUM and ROENTGEN RAYS. 



Consult Letts's Some Fundamental Problems 

 in Chemistry. 



RADIOLARIA, radiola'ria, an order of mi- 

 nute one-celled animals found in the warm 

 seas. They belong to the lowest branch of 

 the animal kingdom (see PROTOZOA), and have 

 the body covered with a tiny shell of silica. 

 After a radiolarian dies its shell sinks to the 

 ocean floor, and the accumulations of count- 

 less shells have caused the formation of thick 

 layers of ooze in many parts of the sea. Fos- 

 sil remains of these shells constitute a large 

 part of the rock known as tripoli and of Bar- 

 bados earth, both of which are used as polish- 

 ing powder. The name of the order has refer- 

 ence to fine threads of protoplasm which pro- 

 ject from the cell body through apertures in 

 the shell and radiate in all directions. 



RAD'ISH, a little vegetable cultivated for 

 the root, which is eaten as a relish or salad. 

 It grows either turnip shape or elongated. The 

 plant is related to the mustard, and above 

 ground looks very much like it except that the 

 flowers are white 

 instead of yellow. 

 The seeds may 

 be sown in very 

 early spring, i f 

 sheltered spots 

 are chosen, in 

 well-prepared rich THE RADISH 



soil, about an inch below the surface. They 

 should not be allowed to mature closer than 

 one in each two inches of the row, and should 

 be ready to eat about three weeks after plant- 

 ing. Seeds may be planted every two weeks 

 during the spring, which insures crisp, good 

 radishes for table use throughout the season. 



The food value of the radish is low, and 

 as a heat producer it has very little value 

 only 135 calories per pound (see CALORIE). 



RA'DIUM, the most costly and most won- 

 derful substance in the world, valued at $9,000,- 

 000 a pound, was discovered in 1898 in Paris by 

 Professor and Madame Curie. Radium is a 

 simple substance, or an element, and in its pure 

 state looks like silver, but it is used in the 

 form of a chloride which resembles common 

 salt. Radium is a hundred times more precious 

 than diamonds, in proportion to its weight. A 

 glass tube of this substance which looks like 

 a bit of fine straw and is shorter than a pin is 

 worth $4,000. The wonders of radium are not 

 yet fully known, and the cause of its intense 

 activity has never been explained. 



Properties. Radium gives off but little light, 

 and its activity is learned only through the 

 effects produced. It gives off enough heat to 

 melt its own weight of ice every hour, or to 

 raise its own weight of water from freezing to 

 boiling point. When a tube of radium is placed 

 on a surface coated with sulphite of zinc, or 

 some other similar substance, the screen be- 

 comes luminous. It discharges electrified bodies 

 and makes any gas on which it acts a con- 

 ductor of electricity. It affects photographic 

 plates. If a photographic plate is wrapped in 

 black paper and an opaque object such as a 

 penny is coated with radium and laid upon 

 the paper with the coated side up, a picture 

 of the object will be produced on the plate. 



Radium destroys the life in seeds, and causes 

 severe burns and ulcers when placed near the 

 flesh, even for a short time. Tubes contain- 

 ing it cannot be safely handled with the bare 

 hands. Radium and some other like substances 

 when dissolved in water produce a peculiar 

 emanation or gas that is used in the treatment 

 of certain diseases. This intense activity of 

 radium does not cause appreciable loss of 

 weight or power. It is estimated that the 

 number of atoms lost is so small that during 

 a period of over 1,700 years a quantity of 

 radium would lose only half its weight. 



Uses in Medicine. The action of radium 

 upon the tissues of the body makes it a valu- 

 able agent in the treatment of superficial can- 

 cer, for the removal of scars, warts and corns, 

 and in the treatment of that form of goiter that 

 causes the eyes to protrude from their sockets. 

 The radium may be applied directly to the 

 part to be treated or it may be given inter- 

 nail}' in solution. So powerful an agent re- 

 quires care and skill in its use. See CANCER. 



