hillebrand.] NOTES ON TYSONITE AND BASTNASITE. fi5 
often with gas bubble. Minute, clear, cuboidal crystals, apparently 
isometric, were also noted in some of these cavities." 
The composition of the minerals was found to be as given by Allen 
and Oomstock, with the exception that the ratios of cerium oxide to 
the oxides of the lanthanum group are not quite the same. The 
formula' are not thereby affected. 
Cerium was separated from the lanthanum group oxides by two pre- 
cipitations by potassium hydroxide followed by long introduction of 
chlorine. After recovery of the earths remaining in solution, they 
were again subjected to this treatment to be certain of having all the 
cerium. In one case a small portion was thus recovered. The cerium 
was most carefully examined for thorium and tiaces of what appeared 
to be thoria were found. The other earths were wholly precipitable by 
potassium sulphate with exception of traces of what may be oxides of 
the yttrium group. Approximate molecular weight determinations of 
the combined oxides of these two groups were made, and they show an 
appreciable difference, which may, however, be due to the uncertainty 
of the method. It may be mentioned that on ignition of the sulphates 
of these earths they acted like the old didymium in that they lost 
exactly two-thirds of their S0 3 on ignition over the full flame of the 
Bun sen burner, a fact which would seem to exclude the presence of 
lanthanum. Their solutions were pink and gave pronounced absorption 
spectra. The ignited oxides freed from cerium were a dull, dirty brown, 
which became nearly white on blasting and acquired a distinct bluish 
cast on ignition in hydrogen. No appreciable reduction in weight fol- 
lowed heating in hydrogen. The material saved is at the disposal of 
anyone desiring to examine these earths spectroscopically. 
Owing to the great difficulty in effecting complete decomposition of 
the minerals by sulphuric acid at a single treatment, the fluorine was 
obtained in condition for estimation by fusing with potassium car- 
bonate after mixing with silica in the proportion of 0.0 gram mineral to 
1 gram silica. 
Fragments of tysonite when held in the blast gave a distinct crimson 
flame showing the lithium red line, but an alkali determination failed 
to reveal more than a trace of this element. 
Of the bastnasite very little pure material could be separated, and it 
was therefore impossible to place with certainty all the loss shown by 
the analysis, but a portion of it is to be charged to the oxides of the 
lanthanum group because of an accident. 
Specific gravity of the bastnasite 5.12 at 27° C. and of the tysonite 
3.10 at 28° 0., which becomes 6.14 when corrected for 2.05 per cent of 
bastnasite. 
Bull. 167 5 
