308 SUPPOSED COBALTIC ACID* 



and of mercury j 3. The nitrate of mercury is thrown down of a flraw co- 

 lour ; and this phenomenon is alfo prefented by the arfenic 

 acid. 



and lime water j 6. It precipitates lime water in a white coagulum infoluble 

 in water, but not infoluble in an excels of acid, as Citizen 

 Brugnatelli affirms ; for in fact, it is re-diifolved with the fame 

 facility in the pretended cobaltic acid as in arfenic acid. I 

 think the miflake of Citizen Brugnatelli arifes from his not 

 having ufed a fufficient quantity of acid. 



and acetite and 7. j t precipitates the acetite and the muriate of barites. I 



muriate of ba- „ . . * . . ... ~ n ,. „ 



riles } from am allured that this precipitation arole from a Imall portion 



impurity. of fulphuric acid contained in the acid called cobaltic. The 



arfeniate of cobalt alfo renders thefe folutions cloudy. 



Precipitates in- 5. It forms an abundant yellowifh precipitate with the 

 fufion of galls. ± . _ r .. . ; _ . ,* , , r . 



tincture ot nut gall newly made. It is known that the arienic 



acid produces the fame phenomenon. 



9. The laft trial. This laft experiment appears to have 

 been coniidered by Citizen Brugnatelli as the molt character 

 The pretended riftic of his cobaltic acid. He found that alcohol feparated 

 feparable from ms ac *d n " om i ts aqueous folution, and alfo that the arfenic 

 water by alcohol, acid diflblved in alcohol enjoys the fame property; by thefe 

 coho^Ic folution P r °ceffes he obtained his concrete acid. This property of the 

 of arfenic acid, cobaltic acid at firft furprifed me ; but prefuming that I ihould 

 difcover the explanation by examining the acid thus precipi- 

 tated, I fubje&ed it to the following experiments. 

 This precipi- i. When heated upon charcoal by the blowpipe it emitted 



Tut aiTeniiTby wmte vapours very eafily diftinguilhable to be thofe of arfenic. 

 heat j 2. A fmall portion heated with borax communicated a vio- 



rendered borax ] e t colour. 



The 'reci itat- *** This acid being precipitated by alcohol alone I examined 

 in g alcohol has the liquid, after having feparated it by the filter. Sulphurated 

 acquired arfenic hidrogen produced an abundant yellow precipitate, which 



was found to be a fulphuret of arfenic. 

 The acid preci- 4, The feparated acid was fcarcely at all foluble in water. 

 fnfoluble'iiTwa" 5 * When mixed with a few drops of arfenic acid it diflblved 

 ter j completely, and refumed its original properties, 



but became (o- From thefe trials I concluded, that the acid of Citizen 

 of arfenic acid. Brugnatelli could be nothing elfe but the arfeniate of cobalt 

 Hence the acid dilfolved in an excefs of acid. 



of Brugnatelli To put this beyond doubt I diflblved pure oxide of cobalt 

 cebaltdifltfjvod m ^ e ar fcnic acid j I evaporated the folution to drynefs, and 



added 



