1870.] 



of Zirconia and the Oxides of Uranium. 



205 



neither can be seen, especially if care be taken to use excess of zirconia. 

 If, however, the amount of uranium be very small, and so much of other 

 oxides be present as to make the bead very dark, or too opaque from 

 deposited crystals, before it is sufficiently concentrated for the compounds 

 with the oxides of uranium to crystallize out, it may be impossible to detect 

 it. In order to apply the test in the case of complex minerals, a bead of 

 borax, boric acid, and pure zirconia should be prepared, then a small 

 quantity of the mineral added, and, after fusion and sufficient concentration, 

 the bead made to crystallize in the manner already described. If needle- 

 shaped crystals be not deposited in the bead when very hot, and if it do 

 not suddenly turn opaque when reheated, the result may not be satisfactory. 

 In this manner it is easy to detect uranium in -^- Q grain of such minerals 

 as Fergusonite, tyrite, and yttrotantalite, even when they contain no more 

 than 1 or 2 per cent. If in such cases the spectrum of the uranous com- 

 pound cannot be obtained, the bead should always be named and reexamined, 

 to see if that of the uranic compound is thereby developed. 



In a similar manner we may make use of a little oxide of uranium to 

 detect zirconia ; but the test is far less delicate than the converse, because it 

 is almost impossible to obtain the compound in a crystalline state, unless 

 there be an excess of zirconia. Not more than tFtTF g ram °f uranic oxide 

 should be employed, or the bead may be too opaque. There is no difficulty 

 in thus detecting zirconia in zircons, or in katapleiit ; but the presence of so 

 much of other bases in minerals like eudialyte prevents our obtaining a 

 satisfactory result. There certainly could not be a more characteristic test 

 to confirm the results of other methods, or to identify such a small quantity 

 of approximately pure zirconia as could not easily be distinguished in any 

 other way. 



The only other compound of uranic oxide of very abnormal character 

 which I have so far discovered is that with cericic oxide. So much of both 

 oxides should be fused with borax in the oxidizing flame as will yield a bead 

 which is perfectly clear, and of pale yellow colour when rapidly cooled, 

 but crystallizes when gently reheated. If the constituents be present in a 

 certain proportion, it then turns from pale yellow to a deep blue, as though 

 coloured by oxide of cobalt. In mos cases the bead is rendered nearly 

 opaque by the number of crystals ; but sometimes, though it turns deep 

 blue, it remains transparent, owing to the compound being set free in a 

 state similar to that of the red oxide of copper in a borax blowpipe-bead, 

 with carbonate of soda and oxide of tin, treated in the reducing flame. 

 The spectrum of these blue beads shows no absorption-bands, but merely 

 a general absorption at the red end ; and it is curious to find that the com- 

 bination of two yellow substances gives rise to a deep blue, in much the 

 same manner as when the yellow ferrocyanide of potassium is added to a 

 yellow ferric salt. The production of this blue colour on the addition of a 

 little uranic oxide might be employed with advantage to identify moderately 

 small quantities of cerium, even when mixed with a number of other 



