Ammoniuret of Cobalt, l^twAcid. 37 



bodies. The ammoniuret of Qpbalt is that to which I direfted my firft refearches*, and I 

 now fend you an account of the peculiarities they have offered. 



I. I had feveral times obferved that the precipitate, formed by ammonia in the folution 

 of the nitrate of cobalt, was rediflblved in that alkali. I collefted this precipitate on a filtre> 

 and waflied and dried it. Its colour was dark. Upon half an ounce of this precipitate I 

 poured two ounces of liquid ammonia, after which I clofed the bottle, and left the mixture 

 at reft ; the temperature of the atmofphere being 20° above the zero of Reaumur, At the ex- 

 piration of 24 hours the alkali had acquired a deep red colour f , and the precipitate was en- 

 tirely diflblved. I fuppofed I had formed a perfeft ammoniuret } but neverthelefs I 

 endeavoured to procure a larger quantity by other means. 



I attempted without efFe£t to dilTolvc fmalt, or the blue (glafs) of cobalt, in cauftic ammo- 

 nia, even with the affiftance of long continued digeftion; but folution took place without 

 difficulty with tlie grey oxide of the fame metal, commonly called ZafFre. This fubftance 

 afforded me an eafy means of procuring the ammoniuret in abundance, and to repeat and 

 vary my experiments in feveral different manners. 



3. I evaporated the ammoniuret obtained from zaffre to drynefs. The concrete refidue 

 which I obtained was compofed of two very diftindt fubftances, one of which was of a deep 

 red colour, and the other of a pale yellowifh tinge. 



4. I poured diftilled water upon this reCdue, agitating the mixture with a fpatula of glafs. 

 The red portion was totally diffolved, and communicated a beautiful rofe-colour to the 

 water. The yellowifli matter remained undiffolved. 



J. The yellowifh fubftance maybe obtained by evaporating the liquid ammoniuret, from 

 which it is feparated, the moment the fluid is reduced to half its original bulk. The red fub- 

 ftance remained diffolved in the laft fourth part of the liquid X- 



6. Ammonia therefore takes from zaffre in its folution two very diftinft fubftances, of 

 which the one foluble in water has a red colour, and the other infoluble in the fame liquid 

 is yellowifh. This laft fubftance is the pure oxide of cobalt. We think we have difcovered 

 a peculiar acid in the former, diftindt in its properties from every other known acid.. 



Concernwg the pure Oxide ofCobalii 



7. The yellowifli fubftance which is feparated by flow evaporation in the air, or in the 

 fun's light, may be conlidered as the pure oxide of cobalt. In fadt it is infipid, inodorous,, 

 infoluble in water, and foluble in the mineral acids. The nitro-muriatic acid forms with it 



• I have fince examined the ammoniuiets of mercury, zlnk, copper, and arfenic. B. 



+ Bergman cbferved only that ammoniae aflumed a red colour with cobalt. " Cobaltum," fays he, "a 

 " niccolo difFert quod omnibus acidis et alcali volatile folvatur colore rubro." This circumftance has been 

 repeated by chemifts without addition. B< "■ 



— t A yellow matter is Separated from the ammoniuret of cobalt,, if kept for a time, even in well clofed 

 battles. B. 



'4 a yel- 



