187.2.] Capt. W. A. Iloss on Pyrology, or Fire Analysis. 



463 



him that the fact itself has been utterly passed over by writers on the sub- 

 ject hitherto, and that the real analytical value of B, therefore, has remained 

 unknown. 



Oxides of Cerium, Didymium, and Lanthanum. 



61. If a good specimen of the mineral "cerite" be powdered and ap- 

 plied to a bead of B in an 0. P., the following phenomenon results. The 

 substance appears to separate into three distinct parts : — (1) red-brown 

 and resinous-looking round spots appear near, but not on the surface ; (2) 

 other round spots, more bulky or puffed out, nearer the middle of the bead, 

 of a pale buff colour ; (3) a slight milky turbidity through the bead, as 

 though a finely divided precipitate were suspended throughout the whole 

 mass. If what is sold or made by the chemists as " pure oxide of cerium " 

 (generally a nut-brown powder) be applied to a S bead in like manner, 

 precisely the same triplicate separation occurs, only the turbidity is very 

 much less. 



62. These round spots are observed to be round through a lens when 

 viewed in every direction ; they are therefore sphericles or globules *, 



After considerably long treatment with O. P. the smaller buff-coloured 

 globules will be dissipated throughout the bead, causing more turbidity 

 with a slight shade of buff in it ; but the red resinous globules remain un- 

 changed, appearing white-hot in the red-hot bead (from which it appears 

 that their fusing-point is higher than that of B), and may be collected, from 

 their superior specific gravity, at the bottom of the bead, by careful mani- 

 pulation with the point of the blue pyrocone, into one large globule. 



63. Professor Stokes has found that, by treating this B bead with dis- 

 tilled water, the general mass is dissolved while the contained globules 

 remain intact, the most minute of which may be thus perfectly extracted. 

 They may be also extracted more quickly, but with less precision, by 

 wrapping the bead when quite cold in paper, and tapping it gently upon 

 an anvil with a light hammer, when the matrix breaks away from the 

 globules. Added to a bead of P under O. P., the red globule first fuses 

 to an intensely lemon-coloured mass on the surface, and then dissolves in 

 the glass with effervescence, giving the reactions of eerie oxide. These red 

 eerie globules have been discovered by Professor Stokes to contain also 

 oxide of didymium i the absorption-bands of which, when spectroscopically 

 examined, they show very distinctly. 



64. It is therefore assumed that the red balls are composed of eerie + 

 didymic oxides, and the buff-coloured ones of lanthanic oxide ; while the 

 turbidity is proved beyond reasonable doubt to be caused by lime, which 

 with baryta are the only substances, except phosphoric acid, capable of 

 causing this opaline turbidity on Jirst application to the B bead f. At any 



* This was written before the writer knew how to extract these globules : vide next 

 paragraph. 



f A trace of phosphoric acid applied to a bead of boric acid and heated in O. P. 

 affords a glass when cool having an almost perfect resemblance to an opal. 



