64 CONTRIBUTIONS TO MINERALOGY. [bull. 2ft 
clear glass}^ residue appeared to be improved in appearance and th 
specific gravity of two samples, each composed of small grains uniforr 
in size for each sample, had risen from 4.596 and 4.590 to 4.654 a 
23i°C. and 4.646 at 26° C, respectively. The two sizes were the 
mixed, giving one sample of about 4.65 sp. gr. at 25° C. That of th 
unpuritied material analyzed by Mackintosh was 4.575. 
Qualitative tests showed the absence of zirconium, glucinum, an 
aluminum and the presence of a little more than a trace of fluorine, o 
a very little carbon dioxide, besides some other gases which were se 
free by treatment with acids and by fusion with an alkali carbonate] 
Silica was separated by two evaporations with hj'drochloric acid 
lead was then thrown out by hydrogen sulphide. 
The earths when finally collected together free from all iron, man 
ganese, uranium, titanium, phosphorus, calcium, and magnesium 
were ignited and weighed. No filtrate from a precipitate of eartl 
oxalates was ever regarded as free from earths till after evaporating 
igniting, and retesting. This is a needed precaution in all simila 
analyses. 
The combined earths were dissolved in nitric acid and evaporated t 
dryness. A saturated solution of potassium sulphate was poured upo 
the dry mass, which wholly dissolved but almost at once began to d( 
posit double sulphates. Solid potassium sulphate was then added i 
crystals. After twenty- four hours the precipitate was collected on 
filter and washed Avith the precipitant solution. Twice was this pr< 
cipitation repeated after first dissolving the double salts in acid, pr< 
cipitating by potassium hydroxide, washing, redissolving in nitr: 
acid, and evaporating. Then onty was the extraction of the yttriun 
erbium group practical^ complete. From the combined filtrates t\ 
soluble earths were thrown out, reconverted into nitrates, and agai 
treated with potassium sulphate, whereby a little further insolub 
matter was obtained. Yttrium-erbium oxides obtained from the ox, 
lates gave a light-colored mixture of 265.6 Mol. W. (108.8 At, W. , 
which furnished a pink nitrate solution showing the erbium absorjij 
tion bands strongly marked, with Very faint indications of the stronj • 
est band of the didymium components. 
The insoluble sulphates were converted into chlorides and thH 
treated with potassium hydroxide and chlorine to precipitate thoriu ij 
and cerium. From the filtrates the soluble earths were recovered ai : 
subjected to a repetition of this treatment. Their oxides after puri 
cation were light dirty brown when heated over the Bunsen flame, b 
grayish white when blasted. Their Mol. W. was 335.5 (At. W. 143/ 
their nitrate solution was pink and gave the characteristic didymiuij 
component absorption bands altogether free from those of the erbiu ij 
constituents. 
