144 CHEMICAL DISCOVERY AND INVENTION 



was the bromide of the previously unknown element about to 

 become so famous under the name of radium. 



According to Professor Rutherford the amount of radium 

 present in a mineral is uniformly about 34 parts for 10,000,000 

 parts of the uranium present. Consequently in a mineral con- 

 taining 3 kilograms of uranium there is present about 1 milli- 

 gram of radium. 



The process of extracting radium on a large scale from pitch- 

 blende residues which contain barium and radium together is 

 extremely expensive and laborious. A complete account of the 

 operations required as well as of the properties of radium 

 examined and recorded up to that date is provided in the Thesis 

 presented by Madame Curie to the Faculty of Sciences of the 

 University of Paris in 1903. This is printed in exlenso in the 

 Annales de Chimie et de Physique. 



The nature of the process has already been sufficiently stated. 

 The first supplies of material were given by the Austrian Govern- 

 ment from the residues left after the extraction of uranium 

 from the pitchblende in the State mine at Joachimsthal in 

 Bohemia. But a company has been formed to work the pitch- 

 blende found in certain Cornish mines. The most productive 

 sources of radiferous ores are at present found in the United 

 States, but as the search for uranium is now proceeding in many 

 countries other minerals will probably be found at least as good 

 as those already known, and perhaps more abundant. The case 

 is parallel to that of the rare earths which fifty years ago were 

 known almost exclusively in connection with Swedish minerals 

 but are now obtained from copious deposits on the other side of 

 the Atlantic. One of the most promising of uranium minerals 

 appears to be the substance called Carnotite, which is a complex 

 vanadate of uranium. 



Radium bromide is still very costly, the price being about 15 

 per milligram at the present time. The enquirer must therefore 

 not expect to see anything more than what appears as a contemp- 

 tible little grain of salt at the bottom of a small glass tube 

 perhaps an inch long. There is, however, a reason other than the 

 cost, which would preclude the exhibition of any large quantity 

 such as a quarter of a pound if at any time so much should 

 become available. Its physiological effects are so powerful 

 that any large quantity is dangerous to handle. 



A small tube containing only a few milligrams was long ago 



