256 M. Atfwedsoti On Uranium. [April, 



was heated by a spirit lamp, in order to drive off any moisture 

 that might have been adhering to the powder, and this moisture 

 was sucked out of the tube by the mouth. The tube was then 

 placed in continuity with an apparatus from which hydrogen gas 

 was extricated from a mixture of zinc and dilute sulphuric acid. 

 This gas was made to pass in the first place through a tube filled 

 with fused muriate of lime in order to dry it. It then entered 

 into the tube containing the protoxide of uranium ; and as soon 

 as it had expelled the atmospheric air, heat was applied to the 

 protoxide by means of an Argand's spirit lamp. The reduction 

 took place immediately, and with such violence that the matter 

 became red-hot. Water was generated, and at the end of the 

 process, which only lasted a few minutes, the green protoxide 

 was changed into a powder of a liver-brown colour. 1*1 87 parts 

 of protoxide of uranium had lost by this process 0*042 part, 

 which amounts to 3*53 per cent. In another experiment 1*468 

 lost 0*052, which amounts to 3*54 per cent. The experiment 

 was repeated once more in a porcelain tube which was heated to 

 whiteness ; but the product was the same brown powder. 



This substance remains unaltered at the ordinary temperature 

 of the atmosphere ; but when heated to the commencement of 

 redness, it takes fire, swells, and is converted into green oxide. 

 It is insoluble in sulphuric and muriatic acids, whether concen- 

 trated or diluted ; but it dissolves with facility in nitric acid with 

 the evolution of nitrous gas, and the solution has a lemon-yellow 

 colour. It is exceedingly probable that the protoxide of ura- 

 nium is by this treatment reduced to the metallic state ; but it is 

 certainly possible that I only reduced it to a lower state of oxi- 

 dizement. 



Meanwhile I undertook some experiments in order to deter- 

 mine the composition of the yellow oxide of uranium, by means 

 of which I expected to be able to throw some light on the ques- 

 tion, whether the substance obtained in the preceding experi- 

 ments should be considered as a metal or not. If I could 

 prepare a neutral salt with peroxide of uranium and sulphuric or 

 muriatic acid, I should have an easy way of determining the 

 quantity of oxygen in the oxide by the analysis of the salt ; but 

 neither'of these salts could be obtained in the state of crystals ; 

 for on evaporating the solutions, I obtained at last a thick syrup, 

 which, when further evaporated, became greenish-yellow from 

 the formation of protoxide of uranium. On the other hand, 

 when I added to the permuriate of uranium a portion of muriate 

 of potash, a triple salt separated on evaporating the liquid in 

 small lemon-yellow crystals. Since hydrogen gas reduces the 

 protoxide of uranium with such facility, I thought it likely that 

 this triple salt might also be decomposed by means of it, and 

 that its analysis could be best performed in the way that Berze- 

 lius proceeded with the analysis of potash-muriate of platinum ; 



