COB

COB

( 310 )

which muriatic acid, or common fait, or muriat folves in this acid without difengaging any gas.of ammonia, or muriatic acid in any form is The green colour of the muriatic folution ap-added, will anfvver as well. Hence the fym- pears entirely to depend upon its concentration,pathetic ink is made at once by digefting zaffre for, when diluted, whether hot or cold it isin nitro-muriatic acid with a moderate heat for rofe-coloured. It appears therefore that thefome time, and diluting the folution with juft black oxyd is in its higheft ftate of oxygenation,fo much water as will make writing appear of and the blue in the leaft, and that the olive anda full green when hot and invifible when cold, brown are in intermediate ftates. With regardAs the nitric or muriatic acid is apt to corrode to the rofe and lilac colours fo common to thethe paper, a ftill better ink is made by adding a folutions of cobalt, it is not certain that the oxydslittle common fait to faturated acetite of cobalt, when dry ever retain thefe fhades, except whenand diluting fufficiently with water. alloyed with arfenic or arfenic acid.

The acetous acid only diflblves the oxyd of The fixed alkalies have fcarcely any actionthis metal. The folution is of a claret red. on cobalt or its oxyds in the moift way, butThe ufe of repeated digeftions in this acid to ammonia diflblves the oxyd with eafe, and thusfree cobalt from iron has already been men- feparates it from iron and fome other metals,tioned. The particulars of this folution have been men-

The action of the arfenic acid on cobalt has tioned in the analyfis. The ammoniated cobaltalfo been noticed in the analyfis of the cobalt is decompofed by potafli, but flowly, whereasores. This folution is rofe-red, and by evapo- the ammoniated nickel which often exifts inration leaves a violet mafs, which again becomes the fame folution is precipitated thereby in ared by digeftion with hot water. This fait cryf- very fhort time.

tallizes without difficulty. Tin&ure of galls added to the acid folutions

Molt of the other acids diflolve the oxyd of of cobalt give a yellowifh white precipitate whencobalt, forming metallic falts but little known free from iron.

and of trifling importance. Prufliat of potaflr caufes a green precipitate

Muriated ammonia digefted with oxyd of when the cobalt is pure,cobalt alfo diflblves a portion and forms a green Cobalt unites with great difficulty with ful-fympathetic ink. phur by artificial combination. Beaume p pro-

_ A triple fait of oxyd of cohalt, ammonia, and jccted fulphur on cobalt in fufion, but the metalnitric acid is alfo formed by adding ammonia to did not appear to be fenfibly altered by it, andnitrated cobalt. Slowly evaporated, this forms all the fulphur burnt off without difficulty,regular cryftals, partly cubical, partly in the Monch q found however that cobalt could belhape of inverted hollow pyramids, according fufficiently fulpliuretted to furnifh a true cin-to the obfervations of Thenard. 0 nabar when afterwards heated with the white

This accurate chemift has alfo given fome oxyd of mercury.

■obfervations on the different ftates of oxidation All the hydrofulphurets combine with thiswhich cobalt is capable of afluming. When metal without difficulty, both in the liquid andpure potafh is added to a folution of cobalt, the the dry way. Hydrofulphuret of potafli addedprecipitated oxyd appears at firft blueifh, but in to a folution of cobalt turns it black, and givesthe air it becomes olive. When wafhed with a black precipitate, which an excefs of the ful-oxymuriatic acid it pafies through fucceflive phuret rediflolves.

fhades of brown red, and finally becomes black. Beaume, on melting in a crucible 4 ouncesThis black oxyd therefore appears to be cobalt of calcined cobalt ore, as much calcined gyp-in the higheft ftate of oxygenation, and when fum, 6 ounces of fait of tartar, and 4 ouncesput into muriatic acid it diflblves therein with of pitch, obtained a ready fufion of the wholedifengagement of oxymuriatic gas, and the fo- mats in the fulphuret of potafh formed in thelution, if concentrated, becomes green, but in procefs (the fulphuric acid of the gypfum beingthe air it foon turns to purple, and immediately deoxygenated by the pitch and then uniting torofe coloured if diluted with water. The brown the alkali), which gave a metallic-looking mafsand olive coloured oxyds alfo give oxymuriatic in large brilliant facets, beneath which was thegas when diflolved in common muriatic acid, earth of the gypfum and other fcoria. Thishut lefs copioufly than the black ox-yd. Alfo if metallic fulphuret was of a golden yellow colourthe black oxyd is heated of a cherry red for and weighed 3 ounefes. It foon tarniflied inhalf an hour it becomes blue, which then dif- the air and deliquefeed entirely. Its folution in

* Thenard. An. Chim. torn. 42. t Thymic . Exper. *• Leonhardi Worterbuch.