Lawrence Scientific School, 855 
double sulphates of sodium and glucinum, aluminum, yttrium, 
_ protoxyd of iron, and sesquioxyd of uranium, are readily solu- 
ble in sulphate of soda and may easily be washed out from the 
highly erystalline insoluble double sulphates of the cerium group. 
In the analysis of minerals in which cerium occurs with one or 
more of the other oxyds, the following method may be employ- 
ed with great advantage. The oxyds are to be brought into the 
form of sulphates, dissolved in the smallest quantity of water, 
and a saturated solution of sulphate of soda added, together 
with a sufficient quantity of the dry sulphate in powder, to sat- 
urate the water of solution. It is most advantageous to use hot 
solutions. The insoluble double sulphates of soda and the ceri- 
um metals separate immediately, as a white, highly crystalline 
powder, which is to be brought upon a filter and thoroughly 
washed with a hot saturated solution of sulphate of soda. After 
washing, the double sulphates upon the filter are to be dissolved 
in hot dilute chlorhydric acid, the solution largely diluted with 
water, and the cerium metals precipitated by oxalate of ammo- 
ia, in the manner already pointed out (4). From the filtrate, 
the oxyds of the yttrium group may be precipitated at once by 
oxalate of ammonia, after peroxydizing the iron by means of 
orine water, and rendering the solution slightly acid with 
chlorhydric or sulphuric acid. The only precaution to be taken 
in this process is to reduce the iron completely to the form of 
protosulphate before precipitating the cerium with sulphate of 
soda. This is best accomplished by means of a current of sul- 
phydric acid gas passed into the hot solution. The precipitated 
sulphates always contain iron when this precaution has been neg- 
lec This iron is easily detected in the filtrate from the oxa- 
lates, and may be precipitated by ammonia and added to that 
obtained from the main solution. 
6. On the employment of fluohydrate of fluorid of potassium in 
analysis. 
The facility with which the double fluorid of titanium and po- 
fassium, or fluotitanate of potassium, separates In a crysta line 
state from hot aqueous solutions, on cooling, suggested to Woh- 
ler the best method at present known for obtaining pure titanic 
acid. In Wohler’s process, rutile or titaniferous iron is fuse 
With an excess of carbonate of potash, the fused mass treated 
with water, which leaves the greater part of the iron undissolved 
and the filtrate saturated with Faediydtic acid. By recrystalliza- 
tion the fluotitanate TiF , KF, or perhaps more correctly, ph ge 
AY, may be obtained in white, scaly crystals, resembling boric 
acid; from this salt pure titanic acid is easily obtained by pre- 
tion with ammonia. Marignac modified this process very 
“Cvantageously in the treatment of zircon to obtain pure zirconic 
