1526.] M. Berzeliui on Uranium. 273 



mentof the uraniate of potash with hydrogen gas, it is obvious 

 that compounds exist containing a still larger proportion of 

 base.* 



From these experiments it follows ; a. That the quantities of 

 oxygen combined with uranium in the oxide and oxidule are to 

 one another in the ratio of 3 : 2. b. That in the neutral double 

 salts which oxide of uranium forms with other bases, that relation 

 by preference takes place, in which the oxygen of both bases is 

 equal; although it might have been expected that the oxygen 

 of the oxide of uranium, as is the case with alumina, and the 

 oxides of iron and manganese would have been thrice that of the 

 alkahne base with which it is associated, c. That oxide of 

 uranium, when acting as an acid, contains either thrice or twice 

 the oxygen of the base. In the first case the oxide is sufficient 

 to saturate the base ; in the second, the soluble base exists in 

 excess. 



We see also that in the analysis of a substance containing 

 uranium, we are exceedingly liable to be deceived by the property 

 which the oxide possesses of carrying down with it during its 

 precipitation all insoluble bases; after the oxide has been 

 ignited, therefore, we ought never to neglect, as M. Arfwedson 

 recommends, to examine whether any portion of it be soluble in 

 dilute muriatic acid, which infallibly detects the presence of a 

 foreign base. 



Uranium has a Very weak, affinity for sulphur. Rose has 

 shown that the sulphuret may be prepared in the dry way by 

 igniting the oxidule in an atmosphere of sulphuret of carbon. In 

 the humid way it may be obtained by precipitating a salt of the 

 oxide with hydrosulphuret of ammonia. The precipitate is 

 black, and is soluble in an excess of the hydrosulphuret, yielding 

 a dark brown coloured solution. Washed and dried, it forms a 

 black heavy mass, which has all the appearance of a metallic 

 sulphuret, but if it be digested in muriatic acid, it proves to be a 

 mere mechanical mixture of the oxidule (which passes into solu- 

 tion) and sulphur. The same spontaneous decomposition and 

 absorption of oxygen from the atmosphere take place, when the 

 newly precipitated and still moist sulphuret is allowed to remain 

 for a few hours upon the filter. If sulphuret of uranium prepared 

 in the humid way, and still mixed with a small quantity of its 

 solution in the hydrosulphuret, be exposed to the air for a num- 

 ber of days, its colour gradually changes to a beautiful flame 

 yellow. The same compound may also be formed by diflusing 

 thehydrated oxide through water, and passing through the mix- 

 ture a current of sulphuretted hydrogen gas ; but if after the 



• From M. Arlwednon's experiment, in which 1'087 gnu. of oxide of uraiiiuni com- 

 bined with 0'iT33 grni. of oxide of lead, retained its oxygen in a red heat, it luijzlit bo 

 concluded that the oxide of uranium retains its oxygen in a red heat, when conibmcd 

 with a quantity of base whose oxygen is no more than one-sixth of the oxide of uranium. 



New aerien, vol.. i\. t 



