THE WORLD’S RADIUM

Otago Daily Times, Issue 18545, 4 May 1922, Page 8

THE WORLD’S RADIUM

SIR ERNEST RUTHERFORD AT THE ROYAL INSTITUTION. <Fbom Ohb Own Cobrebtondent.l ' LONDON, March 14. Sir Ernest Rutherford delivered the first of a series, of lectures on “Radio-Activity’ at the Royal Institution on Saturday. Although the lectures are not exactly intended for the uninitiated . and the unscientific there are bound to be some interesting statements which it needs no scientific training to appreciate. .... The last 25 years of investigation into the, subject of radio-activity had beetn most fertile, said Sir Ernest. It had disclosed new worlds in process of transformation; it had revealed the dissolution of atoms before our eyes. It had disclosed also more than 30 new elements, and at the same time had provided us with the main clues in investigating dhe structure of the atom. Apart from the main direction of advance, it had thrown light on many interesting problems, especially in connection with the internal heat of the earth and the electrical state of the atmosphere. , ’ IIT , One learned much about pitch blend. f it had been said,” remarked Sir Ernest, "that when the Creator got tired of inventing minerals separately He , put the rest into pitch blend.” Certainly, the list of minerals which it contains is a, formidable one. It was from the uranium in this that some of the radium had been obtained. But by far the greater part of the radium came from oarnotite, a mineral found in a sandstone of America. It was also found in Australia and in Cornwall, One ton of the mineral could be obtained from 10 tons of stone, but it needed 500 tons of the minerna to produce one gramme of radium. There were about 160 grammes of radium in man’s possession to-day, the value being in the neighbourhood of £4,000,000. Of this about 120 grammes were in America. Large quantities were used during the war and the bulk of it was undoubtedly in use to-day in various hospitals all over the world. The scientists and men investigating radium and its power to effect the destruction of atoms and the transmutation of metals had only about five or. six grammes in their joint possession. Sir Ernest used for demonstration purposes a tube containing three milligrammes of radium which has been lent t(*-him by the Vienna Academy of Science. The' academy, he said, were always ready to help scientists of whatever nationality, which showed how international their point of view was. A substitute which was being used for radium to-day was meso-thorium. It had most of the properties of radium except the permanency of power. Whereas a milligramme of radium cost £2O or £3O, a milligramme of meso-thorium cost about £lO. The great beauty of buying radium, be skid, was that fraud was so easily prevented. Some time ago a committee, of which he had the honour to be chairman,, had, been set up and standard tubes of radium were agreed upon. These are kept at' the Pittsburg Laboratory. By means of a special type of delicate' electroscope, which was shown in action, the quality and amount of radium in a tube can, be measured. The number of vibrations per minute caused by the proximity of ‘ the standard tube on the sensitive; leaf of the electroscope is first registered, and then ,the‘ material to be tested is brought into contact' and the vibrations of the leaf compared 5 with those sot up by the standard tube. By this process there is no chance of fraud except in one direction. Poor meso-thorium might be mixed with the' radium and the vibrations be as rapid as if it were pine radium. Experiments conducted over several months could detect this fraud, as the power of the meso-thorium •would diminish, while that of radium would remain constant. Radium, said the lecturer, played a valuable part during the ‘ war, being used for making gun-sights and the points of the compass. visible by* night. Use was made of the fact that zinc Sulphide under the influence of the radium rays, became phos-i phorescent, and shone in the dark, and. in order to make luminous paint jt was arranged that a small _ proportion of radium should be used for this purpose. The Government had collected the surplus stocks of tiiis luminous paint, and had extracted about a. gramme of radium from it.' The penetrating power of radium had been used in America for the discovery of some lost radium. It had been recovered from a dust-' heap by means of a portable electroscope used by a physicist, who , soon discovered indications of penetrative radiation. Ho knew that radium was lying somewhere below, and after the refuse had been removed in buckets the missing radium was found.