HOW RADIUM WAS ISOLATED?

Oamaru Mail, Volume XXXIX, Issue 10671, 21 January 1911, Page 3 (Supplement)

HOW RADIUM WAS ISOLATED?

The 'fact -that metallic radium ha: now been extracted from-its salts m briefly announced in these column! some time ago. We are now able tc supply details from an article in llu Scientific American. As is well known until a few months ago -what was popularly called radium was merely some one of the salts of this substance generally the bromide or chloride—tin binary compound of radium, and bromine or chforine. To get the chlorine away from the radium, leaving pure metal, was a task whose difficulty was increased by.the.very small quantities of the salt that were available. -It has finally been .accomplished by Madame Curie, the discoverer of the metal, working in collaboration, with-A. Debierhe. These two experimenters availed themselves of a method suggested by Gunz for the production ot metallic barium involving the .separation of the metal by first combining jt witl mercury, forming an amalgam, and then expelling the mercury by distillation. We'read:' . . , "After some preliminary experiments on barium' . .... Mme. + Cune and M Debierrie ''■• proceeded to. prepare the amalgam of radium by the elec trolys* 3 f a perfectly pure solution of radium chloride, using; a mercury cathode and a platinum-iridium "anode. . - ■■ -Uie amalgam was found to decompose water and to be extremely inconstant tact with air, being perfectly .-liquid ., m opposition to barium amalgam, wliicH under, identical conditions, contains numerous crystals. After being dried, the-amalgam was rapidly introduced into-an iron vessel, previously .reduced in pure hydrogen.. After placing this vessel int&Va. quartz tube, the whole apparatus was evacuated. "The distillation of mercury is an extremely delicate operation- which- should be so conducted as: to avoid even a moment's boiling, -lest some particles ot the substance be projected; . the .experimenters carried out distillation;:-iH in atmosphere of pure hydrogen, keepin'"- the pressure of that gas permanently above tne pressure- of saturated mercury vapor at the temperature of. the iron vessel as determined by the aid. v ot i thermo-electric couple. /.. ;.;■■;■■ "In view of the'very qiiaptibiesof material !r at-the disposal of_the two experimentersV care- had tc- be-taken to warrant an absolute, purity of the avdrogen. : As hydrogen purified and lried according to the ordinary process is-still acted upon by the amalgam-and metal, the gas, Defore entering the apparatus, was made to pass through/a platinum tube heated■ • in the ekctruj : urnace." •' ;> '" ~";.:'..'■'.■ '.. • , --uu The writer describes at some lengtn the process of distillation, which .was. Doth delicatevaiid tedious, and which: vas carried forward, until the metal be'an to, give out vapors whicli would at-:, 'ack the quartz tube. To quote agam> "The iron-vessels were then found. to. ;o'ntain a brilliantly white metal,' Which it about 700 degrees C. would begin-to iiclt- suddenly : arid which, ; in the experimenters' opinion, is practically pure ; adium. -?Tho 'nietal..would adhere itr.origly-io the iron, .teng" separated herefrom with some dimculty: : _ "Metallic 'radium "is ; altered .very •lipidly iit' 4;hc contact- "with air, being ilack'ened mstantaneously, m consequence,: it" a hitrogeii i comlouhct being "formed.- ■>" Some metal parties liaVing been scratched off with a small metal tool, one of them, on being hopped on white paper, was found to iroduca a dark spot as by combustion. ")n coming into contact with water, •licse metal particles instantaneously decomposed, the latter most energetically, lissolving the greater part ot it, which voitld seem to show the solubility of the ixidc. A blackish residue, which doubtess is the nitrogen compound produced iv the reaction of the metal and air, vould be dissolved nearly eompletelv liter adding a very small quantity of ivdrochlorio". aoid. Haviug been dissolved practically completely m the dinted acid, the metal could not contain my appreciable amount of mercury. "The iron vessel containing the renainder of the' metal was then mtroluced into a tube which was sealed in he vacuum. This is to. serve m measurng the penetrating radiat-idli of the netal and ascertaining whether its ■adio-active properties really correspond ,o theoretical calculations. "Though the radio-active .equilibrium la-s not yet been reached, tie first tests

wotdd seem to show the increase of activity to occur in accordance with the law of the production of emanation, the limit; of radio-activity of the metal being about normal. "As -metallic radium is .much more volatile than barium,- the two experimenters expect to purify it by sublimation in the vacuum on a cooled metal plate."