POLONIUM, an element discovered by Mme. Skiodowska Curie (1898), who, while ex amining some samples containing uranium ob tained it from the complex mineral pitch-blende. Mme. Curie named it polonium in memory of her native land, Poland. Pitchblende is a peculiar and very complex mineral found prin cipally in Joachimsthal, Bohemia; Cornwall, England, and in some parts of this country, notably Colorado. It contains a large amount of the element uranium and is mined and worked over to obtain that element. It was from the refuse or waste left after the extraction of the uranium that Mme. Curie obtained polonium and afterward the far more important element radium. Polonium closely resembles bismuth in its chemical properties, and is found in com pany with that element when it is separated from the rest of the above refuse during the process of analysis. To separate the polonium from the bismuth is a matter of great difficulty and no sample of polonium has yet been ob tained that is free or even approximately free from bismuth. The method usually used is that
of fractional precipitation of the basic nitrates. A .solution of the mixed nitrates of bismuth and polonium is made in concentrated nitric acid. Water is added until the liquid becomes cloudy. The white solid basic nitrates that sep arate at first contain a larger percentage of polonium than the original mixture dissolved in the acid. This process, repeated many times, gives a solid rich in• polonium. The most im portant property of polonium is its radio-activ ity (see RADIUM). While radium gives off three kinds of rays or radiations called a, 0 and Y. polonium appears to give only one variety, the a rays. Polgnium loses its radio activity slowly, thereby differing from radium. It should be noted that some noted investigators in this field of radio-active substances deny the existence of polonium, claiming it to be merely a radio-active form of bismuth, its radio-activ ity having been induced by its association with radium in the pitchblende.