ADDENDA
Cerium*.
The fubftance called cerium by Hifenger andBerzelius , two Swedifh chemifts, and ochroitesby Klaproth , is an earthy powder of a white,yellowifh, or reddifh-brown colour, and is con-fidered by the former, with whom Vauquelinalfo coincides, as the oxyd of a new metal,while it is regarded by Klaproth as an earth,which, like yttria, holds a fort of middle rankbetween the proper earths and metallic oxyds.Upon the whole we incline to the opinion ofV auqueiin, and {hall therefore in the followingarticle confider cerium as a metallic fubftance.
§ I. Ores.
Sp. I. Cerite. Ochroite of Klaproth . ReddifhTangJIen of Scheele. Falfe Tungden of Elhuyars.
Its colour is between rofe and flefh-red, red-difh-brown and clove-brown ; it occurs maffiveor diffeminated. Its fracture is compaeft fplin-tery. Internally it is fhining. It varies fromfemi-tranfparent to opake. It fcratches glafs,and gives fire with difficulty when itruckagainft the fteel. It is brittle and eafily fran-gible. Sp. gr. 4.53—4.66. _
.before the blow-pipe it is infufible, but be-comes. friable, and acquires a brown colouraccording to Klaproth , but a yellow one ac-cording^ to Vauquelin. It is very fparinglyfoluble in glafs of borax.
Two varieties appear to have been analyfed:that by Klaproth was opake, and becamebrown by calcination ; that by Vauquelin wasfemi-tranfparent and became yellow by calci-nation. The refults are as follow:
Klapr. Vauq.
4, — 2. Oxyd of Iron
o. — 4. Lime
5. — 12. Water
It occurs at BaftnaCs, near Riddarhyttan, inSweden , in gneifs, accompanied by copperpyrites, bifmuth, and molybdena, hornblende,and aftynolite.
»Nich. Svo. viii j>. »ojr.
Analyfts.
The analyfis of cerite is upon the whole bell:conduced in the following way.
a. Having minutely pulverized the ore, weighit, then ignite it and weigh it again; the diffe-rence may be fet down as the amount of water.
b. Digeft the calcined ore in repeated por-tions of nitro-muriatic acid, and when nothingfurther is taken up fufe the refidue with caufticpotafh ; then difl'olve out the mafs by muriaticacid, evaporate to drynefs, and digeft again invery dilute muriatic acid ; the infoluble refidueis Silex.
c. AdcTtogether the muriatic and nitro-muri-atic folutions, and decompofe the whole at aboiling heat by faturated carbonat of potafh.Rediffolve the whole in as little muriatic acidas poffible, heat the folution to drive off thelaft remains of carbonic acid, and add perfectlycauftic ammonia till there is an evident excefs.Separate the precipitate and add to the clearliquor as much muriatic acid as will faturate it,and then throw down from it the Lime in theftate of carbonat, by means of a mild alkali.
d. The ammoniacal precipitate confifting ofthe oxyds of cerium and iron, is to be diffolvedin muriatic acid, and liquid hydrofulphuret ofpotafti is to be dropped in till the precipitate,which at firft will be greenifh, becomes white.The clear liquor being feparated and treatedwith carbonat of potafti, affords a white preci-pitate, which is carbonat of cerium.
e. The greenifti precipitate is to be diffolvedin as little muriatic acid as poffible, and thpfolution being neutralized by an alkali to thepoint of precipitation, fulphat of foda is to beadded, which will throw down a fulphat ofcerium. The refidual fluid being then decom-pofed by ammonia" depofits oxyd of Iron .
f The fulphat of cerium (e) is now to beboiled with thrice its weight of carbonatedfoda, by which it will be converted into carbo-nat, which is to be diffolved in dilute muriaticacid, and again precipitated by carbonat of pot-afh or of foda.
g. ,EThe carbonats of cerium (J and f) arenow to be calcined, by which the pure brownoxyd of Cerium will be obtained.
An. de Ch isn. liv. p* *