a real Acid of Cobalt. 90 



of these experiments evidently showed that the oxide of co- 

 balt itself could not be converted into an acid by a very large 

 quantity of nitrous acid, and repeating the process several 

 times, i did not consider this experiment as sufficiently de- 

 cisive. In consequence of this idea I resolved to repeat it, 

 changing the process a little with a greater quantity of ma- 

 terials. 



Experiment IV. 



Eight ounces of pure nitric acid, of the specific gravity 

 of 1-280, was poured over half an ounce of oxide of cobalt, 

 purified a€ much as possible from arsenic and iron, and 

 distilled from a tubulated retort to dryness ; which was the 

 case in four hours. Durhig the operation there was no ap- 

 pearance of nitrous acid vapours : the liquor which passed 

 over was nitric acid, perfectly pure. The latter was again 

 poured into a retort, and redistilled under the same circum- 

 stances. The phainomena during this distillation were ex- 

 actly the same as before. Having repeated the process with 

 the like result, the saline mass remaining in the retort, 

 which when heated had a garnet red coluur, was dissolved 

 in distilled water and evaporated to dryness in a porcelain 

 dish. It then weighed six drams. When dissolved in 

 four ounces of distilted water, the solution was divided into 

 •two portions, and subjected to the following experiments : 



Experiment V. 



One-half was evaporated to dryness, and the saline mas^ 

 thus obtained was heated in a porcelain dish till the greater 

 part of the nitric acid was decomposed; so that, if any 

 cobaltic acid had been formed, it must have remained with 

 the oxide of cobalt. The residuum had a black and dry 

 appearance, and in the pure state weighed 50 grains. It was 

 digested seme hours with pure ammonia, and boiled for it, 

 qiuirter of an hour, by which means 30 grains of black 

 oxide were dissolved, and formed a beautiful ruby red solu- 

 tion. This solution was then evaporated to dryness, and 

 during this operation the dissolved oxide of cobalt was se- 

 parated in a a;rayish state. Being again dissolved in distilled 

 water, filtcretl and evaporated, the faint ruby red colour of 

 the liquor was changed to pale red inclining to yellow, and 

 a grain of oxide of cobalt was in part separated in yellowish. 

 brown flakes. The dry saline mass was again dissolved in 

 distilled water, and separated by the filter from the sepa- 

 rated oxide of cobalt ; after which the solution was once 

 ■jorc evapuratcd to dryness, and for a short time exposed 

 G y to 



