294 Proceedings of the Royal Physical Society. 



1786, discovered a planet to which the name Uranium had 

 been given. Prior to this date the most common occurring 

 ore of uranium was considered not as one of that metal, but 

 of zinc; however, at the period I have just mentioned, 

 Klaproth came to the rescue, and brought to light an entirely 

 new element. But even this great chemist was mistaken in 

 so far as he considered what turned out to be an oxide of the 

 metal to be the metal itself, and it was not until the year 

 1840, or more than half a century afterwards, that Peligot 

 proved what had hitherto been regarded as metallic uranium 

 to be the protoxide (UO). This ore, which is by far the 

 most plentiful one of uranium, is found in Cornwall, in 

 Saxony, and in Bohemia, and is no other than the now 

 well-known pitchblende, which is essentially uranoso uranic 

 oxide. 



There are, indeed, a number of ores of uranium (such as 

 uranotantalite, Johannite, Fergusonite, etc.), but the only 

 other important one is uranite, in which the uranium as 

 uranic oxide is in combination with phosphoric acid. I in- 

 tended to have shown to the Society a piece of metallic 

 uranium, but from the great pressure upon my time, I am 

 unable so to do, to-night at any rate. Uranium — according 

 to the process employed for obtaining it — may be of a brown- 

 black colour, or it may be almost white, and of great metallic 

 lustre ; or as in its compact form, it may strongly resemble 

 iron or nickel, but it changes pretty readily on exposure to 

 the air. When heated to a temperature of about 207^ C, or 

 about 400^ F., it burns with great splendour, forming by that 

 process the uranoso uranic oxide. 



(At this stage Mr Hunter exhibited and described nearly 

 all the oxides and salts of uranium, and demonstrated their 

 characteristic reactions with re-agents.) 



I have striven for some days past to prepare a specimen of 

 this newly described salt, but unfortunately, although our 

 artificial sources of heat are no doubt very powerful, they do 

 not possess the property which sunlight does of effecting the 

 change — along with suitable re-agents — from uranic to uran- 

 ous compounds. I am consequently unable to exhibit the 

 uranous oxalate to-night ; but if any member of the Society 



