A't'iy Combination difcovered in "Zaffer. 49 



Having thus dated the idea of the fucccffive gradations of 

 the prifmatic colours, contrary to what is commonly fiip- 

 pofed, of each being homogeneous; let us now refer to the 

 fa6i, as it aftiially exifts. But before we examine the two 

 gradations here ftated of the red and blue (if blue be a co» 

 It)ur), we will examine the inltryncdiatc green. 

 [To be continued.] 



X. On a neiu Comhtnatioit difcovered in T^affcr, luhich Bru- 

 gnatelli conjidered as ihe Cobaltic ylcid. Bj C. Dar- 

 HACa*. 



B, 



• RUGMATELLI, in a paper piibliflied in the Annale.s. 

 Je Cbimie for the nionth of IMuviofc, year S, mentions fe- 

 veral experiments on zafilr, or the gray oxide of cobalt, in 

 which he thoucht he had difcovered a new acid. I flialJ 

 give aii account of fomc of thefc e.^cpcriments, and alfo of 

 the properties afcribed to his cobaltic acid. 



Having fuftered zaffer to remain fonie time with ammonia, 

 after a few days digeftion in the flui, he obtained a red liquoi' 

 known under the name of ammomure of cohalf, which he 

 filtered, and evaporated to drvncfs. The concrete refiduum 

 obtained appeared to him to be compofed of two diftinft fub- 

 flancesj one of a dark red, and the other of a pale vellowifli 

 colour. The red part dilfolved in water, and the ycllowifh 

 temained in the filter. This refidmnn he found to be pure 

 okidc of cobalt. The part foluble in water was exaporated, 

 and deprtfited, On cooling, fonie fmall cryftals, which Bru- 

 gnatelli found lo be a combination of the new cobaltic acid 

 with ammonia. The fupernatant liquor ftill pofleffcd an 

 evident charadicr of acidity. 



The author obferves, that his acid could be obtained co- 

 loured or without colour, according to the means employed 

 to obtain It. When the evaporations arc cflc<!^ted by means 

 of fire, thev leave a refidinun, which, when diffolved in water, 

 gives cobaltic acid almoU colourlefs ; while thole cff'crted in 

 the fun give it always more or lefs red. Brugnatclli, de- 

 firous to afccrtain whether his acid was fornied during the 

 operation of which I hcrf fpcak, or whether it cxiCted quite 

 formed in the zafler, boiled for twenty-four hours fix pounds, 

 of this fubftancc in eiu;ht poinids of water. Me filtered the 

 liquor while warm, .and then caufed it lo evaporate. When 



' From the Annaln tie Cbit/tii', No. iit. 

 \ ut. XII. D nduced 



