jg Kcw Acid ohta]ntdfrom ihe Oxide ofCohdlt, 



a ycUowUh folution, which lofes mod of its colour by the addition of a fmall portion of dif- 

 tilled water. 



8. This folution may be ufed as a fympathetic ink, like th^ common muriate of cobalt. 

 Sometimes the acid rcfufei to diflblve the whole of the oxide ; but the folution is com- 

 pleted by tiie addition of a fmall quantity of water. 



9. This folution is precipitated by the prufllate of pot-afli, of a blueifli green, -which 

 does not change. It is not precipitated by the gallic acid, but the folution becomes of 

 a deeper colour. In other refpefts this folution has the fame habitudes as the common 

 folution of cobalt in the fame acid. 



10. The muriatic acid diflblves the yellow oxide very well, and afliimes a very deep green 

 colour, which immediately difappears with the nitrous acid, and alfo by a fmall portion of 

 water. But it is revived again by the addition of a fmall quantity of well concentrated 

 muriatic acid. 



Of the pure Atmnoniuret of Cobalt. 



11. The yellow oxide is totally foluble in ammonia, and forms the pure ammoniuret. 

 Its colour is yellow, and fometimes rofe coloured ; the acids do not decompofe it ; the 

 muriatic acid difcolours it : prufllate of pot-afh gives it a grey colour, and afterwards 

 throws down a precipitate of the fame colour. The fulphuret of pot-afh caufes it to 

 aflume a deep colour, inclining to black, and throws dbwn fulphuret of cobalt *. 



Ccncernhtg the Acid obtained from the Ammoniuret of Cobalt, and its Properties. 



12. The red fubftance of the preceding experiments was feparated from the yellow 

 oxide. For this purpofe I evaporated the liquid ammoniuret in the fun, and when it was 

 reduced to about one-fourth of its volume, and no longer aiforded any yellow precipitate, 

 I filtered it through paper. The fluid was of a deep red colour, like that of cochineal. 

 This liquid emitted no fmell, but its tafte was very {harp. It was expofed to the fun's 

 light till perfedlly dry. 



13. The remaining mafs was diflblved in diftllled water, which acquired a fine ruby 

 colour. This folution exhibited unequivocal figns of acidity. It depofited on cooling" 

 fome fmall brilliant cryftals, which I found to be a combination of the acid with am- 

 monia. This acid appearing to be diftinft from every other, I have thought fit to 

 call it the cobaltic acid. 



In order to afcertain whether heat was capable of ralfing the cobaltic add, I fubmitted 

 one pound of the ammoniuret of cobalt to diftillation in ^ retort. When three-fourths 

 of the liquid had pafled into the receiver, I flopped the diftillation. The retort contained 



* The fulphuret of cobalt, dried in the air, refembles zaffre in its colour. When nibbed on paper, it 

 affumes the metallic brilliancy, as do moft of the other metallic fulphurets. It emits a fulphureous fmcH 

 when heated, and takes fire when thrown on ignited coals. B. 



3 a liquid 



