304 SUPPOSED COBALT1C ACID. 



milar to thofe which the fame fubftances aflume when preci- 



tut does not pitated by the artificial hidrofulphurct of foda. It does not 



throw down the precipitate the earths when diflblved in the acids, excepting 



whence the al- alumine, zircone, and yttria ; which proves that the alkali is 



kali is faturated* perfectly faturated with fulphurated hidrogen gas. 



With fulphate of This fait, when decompofed by fulphate of iron, afforded 



iron it affords hidroiulphuret of iron, and fulphate of foda, which were ob- 



of iion, and ful- ta ' ne( * cryftallized by evaporation and cooling of the liquor; 



phate of foda. whence this fait is a true hidroiulphuret of foda. 



The manufaau- The prefence of this fait in the foda of Meffrs. Payen and 



r ? rs 11 didnot " fc Bourlier, proves that thefe manufaaurers did not ufe a fuffi- 

 chalk enough, r 



&c. ciently large quantity of chalk to faturate the whole of the 



fulphur arifing from the decompofition of the fulphate of foda 

 by charcoal ; unlefs we fuppofe that it is formed during the 

 deco&ion the alkali is made to undergo when extracted from 

 the carbonate of foda. 



Remark. The whole novelty of this obfervation confifts in the pro- 



perty which this fait has of cryftallizing, and the determination 

 of its figure. Its other properties have been defcribed by Ci- 

 tizen Berthollet with great exactnefs. 



XIII. 



Memoir refpeGting a neiu Combination difcovered in Zaffire, which 

 Cit. Br u gn at ell i juppofed to be a peculiar Acid, which 

 he denominated the Cobaltic Acid. By Cit. Darracq*. 



Suppofeddifco- V/ITIZEN Brugnatelli, in a memoir printed in the Annales 



Icid bf cobalt! de Cmmie f° r the month of Pluviofe in the year 8, page II 3 f , 



by Brugnatelli. relates various experiments upon zaffre, or the grey oxide of 



cobalt, from which he concluded that this fubftancc contains a 



new acid. I fhall defcribe fome of thefe experiments,, as well 



as certain properties attributed to his cobaltic acid. 



He digefted zaf- He took zaffre, which he left in digeftion with ammonia. 



filterLfTndTva' ^ ter f° me days maceration in the fun he obtained a fluid of 



porated to dry- a red colour, known by the name of ammoniuret of cobalt, 



nefs. The refi- wn ; c h [ ie filtered and evaporated to drvnefs. The concrete 



due gave oxide . ~~1 . 



and the fuppofed refidue thus obtained appeared to him to eonfift of two very 



new acid, united diilincc. fubftances, one of a deep red colour, and the other of 

 with ammonia. r 



* Annales de Chimie, No. 121. Vol. XLI. p. 66. 

 ■f Philof, Journal, quarto, IV. 36, 



a pale 



