262 M. Arfwedton on Uranium. [April, 



was collected on a filter, and hastily washed with fresh boiled 

 water, to prevent any mixture of carbonate of barytes. The 

 uraniate of barytes, after being dried and heated to redness, had 

 a fine yellow colour, which became lemon-yellow when the salt 

 Was reduced to powder. 



1-343 gramme of uraniate of barytes previously heated to 

 redness, being dissolved in nitric acid, and decomposed by 

 means of sulphuric acid, gave 0-295 gr. of sulphate of barytes, 

 or 0-194 barytes. The solution which contained the peroxide of 

 uranium was evaporated to dryness, and the dry salt heated to 

 decomposition in a platinum crucible ; for this a strong and long 

 continued heat was required to drive ofT the last portion of the 

 sulphuric acid. The residue was protoxide of uranium, which 

 weighed 1-121. When dissolved in nitric acid, no turbidness 

 appeared indicating the presence of any sulphate of barytes : 

 1-343 uraniate of barytes had thus given 0-194 barytes, and 

 1-121 protoxide of uranium, making together T315. The loss, 

 amounting to 0-028, must of course be the difference between 

 the quantity of oxygen in the protoxide and peroxide of ura- 

 nium; but 1-121 : 0-028 :: 100 : 2*5 ; consequently 100 protoxide 

 of uranium, in order to become peroxide, must combine with 2-5 

 oxygen. 



T456 gr. uraniate of barytes of another preparation gave 

 0-364 sulphate of barytes (equivalent to 0-239 barytes), and T186 

 protoxide of uranium. The oxygen driven off in this experi- 

 ment is 0-031 with 1-186 protoxide; this to 100 parts is equiva- 

 lent to 2-61. The mean of 2-50 and 2-61 is 2-55; and 100 

 parts of peroxide of uranium ought, according to these experi- 

 ments, to contain 5-96 oxvsen, and 100 of the metal combine 

 with 6-34 oxygen, in order to become peroxide. 



Although the uraniate of barytes was formed in both cases 

 in the same way, so that the liquid from which it was prepared 

 contained always a quantity of uncombined ammonia; and 

 although a quantity of muriate of barytes in both cases remained 

 unprecipitated in the liquid, yet we perceive that the uraniate 

 of barytes first prepared contained a considerably smaller pro- 

 portion of basis than the second. It is possible that the peroxide 

 of uranium, being a weak acid, may undergo some modification 

 in its capacity of saturation, according as the muriate of barytes 

 is present in a greater or smaller proportion relative to the 

 muriate of uranium. 



Analysis of the Sulphate of Uranium and Potash. 



This double salt being less soluble in water than the muriate 

 of uranium and potash, crystallizes more readily, and may, by 

 means of crystallization, be completely freed from any excess of 

 the salt of potash, I consider this salt on that account as more 

 suitable for analysis than the muriate. 



Potash-sulphate of uranium is obtained by evaporating a 



