49 New Acid obtaintdfrom the Oxide ofCohalt 



20. With the faturated folution of foda, it affords an irregular tranfparent fait foluble 

 in water, and not deliquiefcent. 



21. With pot-afli it affords a cryftallizable fait in fquare cryflals, which are tranfparent 

 and permanent In the air. 



,22. With ammoniac it forms a fait foluble In Its acid. 

 23. With barytes it forms an opake fait, cryftallizable with difhculty. 



Supplement. 



The prefence of an acid In zaffre, Induced me to fufpe£l: that it might probably be ar- 

 fenical : but this doubt foon vanifhcd, by comparing the charafters of each. 



I. The arfenical acid does not precipitate the folutions of fdver, as does the cobaltic 

 acid. 2. The arfenical acid precipitates lime water ; this arfeniate is re-dilTolved by the 

 acid, as well as by a new quantity of lime water. The contrary happens with the acid of 

 cobalt. 3. The arfenical acid does not decompofe the muriate and acetite of barytes, as 

 does the cobaltic acid. 4. The arfenical acid is foluble in alcohol, which precipitates the 

 cobaltic in a concrete form. 



It remained to be proved, whether the acid obtained from zafFre exifted ready formed in 

 that oxide, or whether It was produced by the adlion of the ammonia. 



As the acid of cobalt Is very foluble in water, I boiled fix pounds of zafFre in eight 

 pounds of water for a quarter of an hour, and filtered the liquid while yet warm. That 

 which pafTed was tranfparent and colourlefs ; but had a perceptible tafte. I evaporated the 

 liquid, taking care to cover the vefTel with a piece of filk. When It was reduced to one 

 half, it became turbid, but the matter which was feparated was not perceptibly coloured. 

 1 continued the evaporation till no more than one-third of the liquid remained, and then 

 removed it from the fire. It depofited a very white matter, which the contaft of the air 

 changed to a beautiful rofe colour, I feparated this matter, and colIe£led it on the filtre. 



The filtered fluid was of a bright yellow colour, and perfctlly tranfparent. It had a 

 very decided acid tafte ; reddened the tindure of turnfole, fpeedily decompofed lime water, 

 the falts of barytes and of Giver, was precipitated by alcohol, &c. In a word, its habitudes 

 were in every refpedl the fame as thofe of the cobaltic acid obtained by the foregoing 

 procefTes. 



The red depofition which remained on the filtre had no tafte, and coloured the muriatic 

 acid of a very fine green. It was the pure oxide of cobalt. This oxide is largely foluble in 

 its own acid, and is precipitated in proportion as the acid is concentrated. 



The acid which the ammonia feparated froni the zaffre, exifts therefore ready formed 

 in that fubftance. Its radical ftill remains to be pofitively afcertained. In the mean time 

 I have thought it proper to defignate it by the name of the Cobaltic Acid. 



X. The 



