OC. Hl. Wing on certain Double Sulphates. B57 
solved, again precipitated, and this process repeated till six 
successive precipitations as a basic salt had been effected. The 
final precipitate was dissolved in sulphuric acid, reduced by 
sulphurous acid, the solution evaporated and the excess of acid 
expelled by heating in, what I shall, for brevity, term a “radi- 
ator.” This is a crucible of sheet iron in form like the ordin 
porcelain crucible, midway in which is fixed a triangle of plati- 
num wire by which a smaller crucible may be supported so as 
to leave a space of about 2 c. m. intervening between the walls 
of the two crucibles. The substance being placed in the inner 
crucible and the heat of a Bunsen gas lamp re to the outer 
one, a very uniform heat may be maintained, variable at will, 
to a temperature considerably above the boiling point of sul- 
phurie acid. 
The neutral cerous sulphate thus obtained was dissolved in 
cold water, filtered, and crystallized by slow evaporation on the 
r bath. 
A saturated solution of this salt was placed in a 12-inch sac- 
charometer tube before a powerful spectroscope, and light, con- 
densed by a ‘ bulls eye” lens and transmitted through this tube, 
howed no traces of didymium. is 
The cerium also from the mother liquor from the last precipi- 
tation as basic salt, subjected to the same rigid test proved free 
m didymium. 2 
The first precipitation of basic sulphate was of a dirty buff, 
every 2 ieee | one lighter in color, the last three being al- 
white. 
The cerous oxalate from both precipitate and mother liquor 
of the last precipitation was of a snowy whiteness, with no trace 
of amethystine tint by reflected light, and gave on ignition a 
white ceroso-ceric ox : : 
The cerous sulphate, the preparation of which has just been 
deserit was, after repeated ¢ lizations, subjected to analy- 
2 
z 
& 
5 
Fs 
| 
$ 
: 
F 
$9 
& 
ou 
: 
EB. 
FE 
ay iti corresponding 
of cerous oxyd, the experiments of J egel* and Wolft made in 
: ’s laboratory, give the following factors. 
Jegel, -9504 9507 _... .--- ---- mean 95055 
Wolf, -9507 -9518 -9494 -9509 °9518 mean 95089 
* Annalen d. Chem. u. Pharm., ev, 1858. } This Journal, vol. xlvi, May, 1868, 
