^O'^ Analjjls of the Atfemates 



of it that happens to be in contaiSl with a filter, becomes 

 green, and then blackidi, leaving a mark of the tame (liade 

 upon the paper. Were it not for this property of changing, 

 it might be of ufe in the art of painting; for the colour is 

 t'xiremelv beautiful, and would be highly valuable if durable. 

 The precipitate caul'cd tn the muriate of copper by the car- 

 bonates of potafh and foda, is of a brighter yelloWy and is a 

 real carbonate of fuboxide of copper. But, if ammonia is 

 poured, at lirll in a fmall quantity, into the al>ove fokition, 

 the precipitate is blue; and, upon adding an excefs ot the 

 precipitant, the whole is rcdiOolved, and the liquor is like 

 any other ammoniacal folution ot copper. 



In order, however, to determine in what ftate the copper 

 was diflblved by that alkali, I poured tome ammonia upoit 

 lOO parts of this fuboxide in a well-clofed phial. The liquor 

 became blue ; and 1 e.Npe<Sled to tind that part of the ore had 

 been reduced, as with phofphoric acid ; but the rcliduum was 

 entirelv foluble in muriatic acid, with the ufual phaenomena. 

 A fplrituous tinfture of galls, poured into muriate of iub- 

 o.xide of copper, aflorded no ])recipitate, owing, I fuppofe, 

 to the excefs of acid ; but fulpiiurated hydrogen gas threw 

 down a black, and prufliate of ammonia a lightilh brown, 

 precipitate. 



I endeavoured to obtain muriate of fuboxide of copper by 

 evaporation, and by diflillation in a retort j but, as I eouH 

 perceive the liquor condantly aflume a blueilh tinge, 1 could 

 not reckon upon the purity of the fall, fufficicntly to fubmit 

 it to analyfis. 



, Such were tha princrpsl experiments, which the fleeting 

 and precarious exiiience of the lalt allowed me to make upon 

 it. But, froiM fome properties \\ hich 1 had remarked, I could 

 ]>frecive that this ore was a natural oxide of copper, nearly in 

 the fame liate as that artificial oxide which Mr. Proud had 

 Ibund in the while muriate of copper, obtained by pouring 

 a lecent Iblutiou of muriate of tiit into a Ibluiion of muriate 

 of copper. 



If, however, by the vcw nature of the fubftance, (which, 

 as I faw it ever changing, I thought it would be lofs of time 

 to examine furth.'r,) 1 have been turned atide from more cer- 

 tain refults, I have been: more fucceisful in imitating by art 

 the dale of this natural produil. 



By expofmg oxide, hydrate, or carbonate of copper, with- 

 out addition, to a violent heat, in- an open crucible, I fre- 

 quently obtained the fuboxide, which then prefented all the 

 properties already recognized in the above fpecies of copper 

 ore. Ill one inllance, I fo far fuccecded, that, upon the very firft 



infpe£lion. 



